Best planetary scope? 8" APO?

[Travis Morien]

Hey guys,

I'm soon to be in a position to buy a medium to large sized apochromatic
refractor, I am looking at the Meade 7" ED apo. I have heard great things about
them, but does anyone recommend another instrument, like an Astro Physics
perhaps? Something in 8" would be good, but Meade don't make them.

Travis

I'd rather see folks doubt what's true than accept what isn't. - Frank A. Clark

[mark d. doiron]

"Travis Morien" <travis...@yahoo.unspam.com> wrote in message
news:Ic6x6.1950$bY4....@www.newsranger.com...

> Hey guys,
>
> I'm soon to be in a position to buy a medium to large sized
apochromatic
> refractor, I am looking at the Meade 7" ED apo. I have heard great
things about
> them, but does anyone recommend another instrument, like an Astro
Physics
> perhaps? Something in 8" would be good, but Meade don't make them

Travis--

i recommend something else--but based on the following testimony:

http://www.starmastertelescopes.com/html/thin-mirrors.htm

i suggest that you also consider StarMaster scopes, especially the 11.5"
el to maximize portability. i'm a big refractor fan (i own four!), but
if you really want the best planetary scope, i think that the StarMaster
will blow away even an 8" apo.

clear, dark skies--

mark d.

[Ron Wodaski]

Just my 2 cents, but I think the best planetary scope is a 12-16" Newtonian
with superb optics (e.g., Starmaster with Zambuto primary). Put it on a EQ
platform, or get one with goto/tracking, and you are in heaven. You need
steady skies to do the best planetary observing any way, so the larger
aperture means a lot. It means the difference between observing at ~600x
with a superb refractor, and at ~1200x with a superb large Newt on those
perfect nights.

My fondest memories of planetary observing so far have been with a 12.5"
StarMaster, a Tom Osypowski platform, and an AP Binoviewer with a couple of
Tak LE eyepieces in it.

--
Ron Wodaski
http://www.newastro.com

"Travis Morien" <travis...@yahoo.unspam.com> wrote in message
news:Ic6x6.1950$bY4....@www.newsranger.com...

[Ron B[ee]]

Although, I'm not seen one nor use one, I think this is the
best planetary scope, IMHO. Go to this link.
http://www.excelsioroptics.com/
Also, go the CCD image place. I think in the case a picture
is worth 1000 words :-). I've never seen such pictures taken
with amateur scopes.

Ron B[ee]
PS Now, how I wish they would make a 6" f/8 version for
a small guy like me.
------------

"Travis Morien" <travis...@yahoo.unspam.com> wrote in message
news:Ic6x6.1950$bY4....@www.newsranger.com...

[WHALEN44]

Hi Travis,

TMB Optical sells APO's up to 16".
For a decent 8" APO, you better have
a lot of ca$h!

If you want the best planetary scope, a 16" APO is the way to go :-)

Richard Whalen
whal...@aol.com

"Time spent observing the heavens is not deducted from your lifespan"

[Reef1969]

Check out Ed Tings review of the 7" meade, or cloudynights.com may have the
review also. I think Ed's site is scopereviews, or telescopereviews.com.

Richard Beasley

[Allen and Jocelyn Chan]

> If you want the best planetary scope, a 16" APO is the way to go :-)
>

A 12" MN comes very close.....8)

Allen Chan

[Alan Figgatt]

Ahem, "great things about them" is not what I would use to describe the vast
bulk of comments about the Meade 7" ED scopes (aka 178 ED). The general
consensus is, as far as I can tell, is that the bigger Meade EDs can vary all
over the map in quality. For the gory details on one, try Ed Ting's site at
http://www.scopereviews.com/178ed.html. Also, there were a series of threads in
saa a year or two back in regards to Chas P. in Florida (aka Chas...@aol.com)
headaches (nightmares?) regarding a 178 ED which he eventually returned.

The smaller ED models, the 4" and 5", generally get better grades. It's the
bigger EDs that apparently have more problems. However, I have personally only
seen 1 or 2 Meade ED scopes; have seen more TV, AP and Tak scopes in person, so
it may be that Meade has never sold that many of them.

If you have the bucks and want a big APO, makes to look at include
Astro-Physics, Tak, TMB Optical, Aries claims they will be shipping APO scopes
someday real soon, or, heck, Chinese Synta or D&G scopes with a Chromacorr
whenever that hits the marketplace. You also may want to check out the refractor
group on yahoo!groups.

Clear skies,
Alan Figgatt

[Bill Foley]

Hi,
See some telescope reviews before going for the 7" Meade - They are
fabulous if you get a good objective, but it is difficult to get a
really good one. One review is at the URL:
http://www.scopereviews.com/
and you might also want to check out
http://www.excelsis.com/vote/astro/telescopes/Meade13/
where there are good and bad reviews.
I think the upshot is, you might get a real winner right off the bat,
but if you do NOT, then be prepared to work with Meade for a long time
to get it fixed...
I don't think AP makes the really big refractor any more, but the 155 or
whatever is bound to be a winner! Also, I have NOT seen any bad
comments about the Meade 5" APO, so they probably have the quality under
control for that. If you have the money, though, go with a AP or a
TMB. Also, do take a look at some of the big Maks (NOT the hamburgers,
the Maksutovs).

--
Best Wishes,

Bill Foley

P.S. Ignore the reply-to address, it is to foil spammers.

[CHASLX200]

>Subject: Best planetary scope? 8" APO?
>From: Travis Morien travis...@yahoo.unspam.com
>Date: 3/30/01 3:42 PM Eastern Standard Time
>Message-id: <Ic6x6.1950$bY4....@www.newsranger.com>

>
>Hey guys,
>
>I'm soon to be in a position to buy a medium to large sized apochromatic
>refractor, I am looking at the Meade 7" ED apo. I have heard great things
>about
>them, but does anyone recommend another instrument, like an Astro Physics
>perhaps? Something in 8" would be good, but Meade don't make them.
>
>Travis

*************************
You heard great things about the Meade 7" ED???

I would stay as far away as i could, from the Meade 7" ED!
I had one i know.

Chas P.

[CHASLX200]

>Subject: Re: Best planetary scope? 8" APO?
>From: "mark d. doiron" delete@markdoiron@yahoo.com
>Date: 3/30/01 4:48 PM Eastern Standard Time
>Message-id: <Xa7x6.4006$ao6.4...@typhoon.kc.rr.com>

>
>Travis--
>
>i recommend something else--but based on the following testimony:
>
>http://www.starmastertelescopes.com/html/thin-mirrors.htm
>
>i suggest that you also consider StarMaster scopes, especially the 11.5"
>el to maximize portability. i'm a big refractor fan (i own four!), but
>if you really want the best planetary scope, i think that the StarMaster
>will blow away even an 8" apo.
>
>clear, dark skies--
>
>mark d.

***********************
I agree Starmaster is the way to go!
I have the 14.5" Starmaster, and it can handle up to 1200x on the planets, when
seeing allows.
Can't wait to see Mars at over 1000x...

Chas P.

[Rockett Crawford]

I second what Ron says. I got to look at Jupiter through a 12 inch
Starmaster at last year's Okie-Tex and it was the best view I have
ever had of it, except for one super steady night when I looked through
a friend's 18 inch Sky Designs dob.

Rockett Crawford

Ron Wodaski wrote:

> Just my 2 cents, but I think the best planetary scope is a 12-16" Newtonian
> with superb optics (e.g., Starmaster with Zambuto primary). Put it on a EQ
> platform, or get one with goto/tracking, and you are in heaven. You need
> steady skies to do the best planetary observing any way, so the larger
> aperture means a lot. It means the difference between observing at ~600x
> with a superb refractor, and at ~1200x with a superb large Newt on those
> perfect nights.
>
> My fondest memories of planetary observing so far have been with a 12.5"
> StarMaster, a Tom Osypowski platform, and an AP Binoviewer with a couple of
> Tak LE eyepieces in it.
>
> --
> Ron Wodaski
> http://www.newastro.com
>

----------------------------------------------------------------------------

Capella's Observatory (CCD Imaging)
http://web2.airmail.net/capella

[Zane]

Travis Morien<travis...@yahoo.unspam.com> wrote:

>Hey guys,
>
>I'm soon to be in a position to buy a medium to large sized apochromatic
>refractor, I am looking at the Meade 7" ED apo. I have heard great things about
>them, but does anyone recommend another instrument, like an Astro Physics
>perhaps? Something in 8" would be good, but Meade don't make them.

You might check out Excelsior Optics' 10 inch planetary Newtonian. I
haven't seen one but he gets unbelievable planetary images. If I were
after a planetary scope I'd look at one before I bought a refractor in the
8 inch size range. (There are some good reasons why there aren't many that
large around these days.)

http://www.excelsioroptics.com/

Zane

[Tim Povlick]

Travis,

I recommend a look at the TMB APOs, exceptional optics
and well crafted instruments. Excellent for visual as well
as astrophotography.

http://www.apm-telescopes.de

Let us know what you decide, if you don't mind..

Clear Skies,

Tim Povlick
San Juan Capistrano

[Dave Novoselsky]

Buying the 178 Meade is like playing Russian Roulette with a revolver with
five of the six chambers loaded -- and perhaps with all six loaded. But
yes, the right large APO will give the best planetary views, inch for inch
and even more than that. However, the issue cannot be resolved that easily.

I can speak from first hand experience since I have an 8" APO, a TMB 203
f/9. It is superb, but I waited a year for it, and like any large APO, set
up and take down is a bear. Once up, the work is worth it, since the views,
particularly of the Gas Giants and 'concentrated' deep sky objects like
M-42, etc were stunning. The image scale on the Moon is not to be
overlooked either, and the only reason I don't try to use it every night is
time and effort. (However, the roll off is going to go up as soon as the
weather settles down. Any 7" + APO needs at least a semi-permanent mount.

So, no matter what other opinions are out there, all things taken as the
same, a big APO is a wonderful thing to have and use. Indeed, there is a 229
TMB f/9 in California. I meet the owner at Astrofest 2000 and he is getting
even more spectacular views in his, which is under a dome. 9" not enough?
If you want more, Tom Back has a 10" APO which I believe he can deliver
later this year.

But having said that, I agree with the others that you can get a marvelous
planetary view with a Carl Zambuto mirror in one of Rick S's GOTO
Starmasters. I differ when they claim an 11 or 12.5 will beat a Tom Back 8"
APO. My 11 EL Starmaster will trounce my 6" AP under good seeing conditions,
but not the 8". I know, they were out the same night pointed at Jupiter
and Saturn this fall.

No, while the 11 and 12.5 ELs will surely provide the best planetary views
for the money, and deliver 6" APO or even more performance, a top of the
line APO will, however, do better in light polluted skies or poor seeing
conditions, where the larger mirror and the central obstruction, albeit
minimal in a top of the line Dob, won't give you the views in the 'soup'
that a refractor will. No, I suggest an 18 or prob a 20"
Zambuto/Starmaster is the way to go toe to toe with an 8" APO, and that will
be the fight of the season as soon as I can get my 8 and 18 out along with
some of my observing friends from Cloudy Nights later this year. Even then,
the contrast issue will still have to be resolved. (Bad pun Dave.)

I have also heard that Maurzio's Newts may be the way to fly. Don't know
first hand, but the photos look great and my phone conversations with him
have been a joy. If he says he can do it, I believe him.

Bottom line is that most of the people you have heard from here are all
right -- to an extent and within the parameters they mention. A large
APO -- and you can prob get Tom to build you one up to 16" with enough time,
and enough $$$ -- is the least 'challenged' of any telescope inch for inch.
It is also the most expensive inch for inch as well. The winner in the
cost per view would be a Dob with one of Carl's mirrors on board. A Newt
with optics like Maurzio maks may also come into the cost/benefit picture
here. Then you have the true 'wild cards' like the 300mm Mewlon (the 250
Mewlon will meet or even beat most 6" APOS, weighs about 27 pounds, and
offers marvelous planetary/lunar views. The 300 should be even better --
but the price goes up from about 6k to a bit more than double that.)

So the list, and opinions, may be endless and all of us are right -- and
perhaps the real answer is there is no one answer -- EXCEPT THIS, DON'T BUY
THE MEADE 178. Dave

"Travis Morien" <travis...@yahoo.unspam.com> wrote in message
news:Ic6x6.1950$bY4....@www.newsranger.com...

[Bill Becker]

Hi Ron B[ee],

Would you believe a 7"? Maurizio is seriously considering this aperture
for his next project.(he used to make 6"ers...not sure of the focal
ratio)
Would you like to stand in line behind me? <g>

Best regards,
Bill

[Bill Becker]

Hi Chas,

No one should have to go through what you did. Travis, listen to Chas.

Best regards,
Bill

[LucaG.]

My Eleven Inch Ultima Celestron Schmidt Cassegrain is among the best
planetary scopes.
Very portable and lots of aperture.

Take a look at my planetary pictures
http://photos.yahoo.com/luca_grella

my best regards

-luca

[vahe sahakian]

> I'm soon to be in a position to buy a medium to large sized apochromatic
> refractor, I am looking at the Meade 7" ED apo. I have heard great things about
> them, but does anyone recommend another instrument, like an Astro Physics
> perhaps? Something in 8" would be good, but Meade don't make them.
>

> Some years ago I decided to go for an 8" apo, at that time I was using an AP 6"
> apo, superb as was it did not have the aperture for serious planetary detail, this
> was before TMB line of large apos. I finally settled for a 10" f/20 TEC MCT, I
> have not compared this scope to an 8" apo side by side but the planetary
> performance is definitely better than any 7" apo that I know of.

> If you live in a moderate climate you should check into large MCT's, a well made
> MCT with small secondary comes awfully close to a refractor in planetary
> performance.

Whatever that you decide, by all means stay away from Meade 7".

Thanks,
Vahe

[Ron B[ee]]

Thanks Bill for the info. 7" sounds even better providing it's an f/7 (or
f/5.6
like the classic Starmaster); I can't take anything more than 48" long :-(.
If so, I'd definitely *cut in line* to get in front of you :-). It's also a
shame
that Starmaster doesn't make the Classic 7" anymore; I bet the wait would
be even longer than for an AP. I think there's a market for a small, light,
and
somewhat portable Newtonian but with *exquisite* APO like quality.
Although,
I'm bias toward a refractor and personally never like a Newtonian, this is
one great exception. Someone told me about the PortaBall, but I don't
like the truss concept and the shroud works poorly.

Do you know when Maurizio is planning to make it? If very soon, I can
junk my current plan for a new scope and wait for his.

Ron B[ee]
-----------
"Bill Becker" <bb...@rmisp.com> wrote in message
news:3AC5569C...@rmisp.com...

[Del Johnson]

What do you have against trusses and shrouds? It is the truss that makes
the high performing large reflector possible for most of us. They have no
liability.

Del Johnson

"Ron B[ee]" <ro...@home.com> wrote in message
news:e5fx6.96680$o7.38...@news1.rdc1.sdca.home.com...

[Chris1011]

>>but does anyone recommend another instrument,>>

You will get dozens of different opinions on what is best, but I will tell you
that for any given type of scope configuration, be it Newtonian, Cassegrain or
Refractor, there will be excellent, just acceptable and rather poor examples
for each type. No one type can lay claim to being the absolute best. If you are
looking for an outstanding planetary scope you should consider the following:

In a Newtonian 8" to 12" with small central obstruction under 20%, very thin
spider, longish F ratio above F6, excellent tube construction with well
ventilated mirror and a decent flotation mirror cell (no mirror glued to
plywood). Shorter F ratios require that the object be exactly centered in the
field to avoid comatic aberrations. Also, the shorter the mirror, the more you
will have to fiddle with the collimation. The mirror should have the best
coating you can afford, avoid cheap coatings that lose contrast over time. Get
a coating that you can clean without introducing pinholes. Add to that a smooth
functioning focuser and you will have a very effective planetary instrument.

In a Cassegrain (this includes open and closed tube systems, Dall Kirkam,
Maksutov, classical, Schmidt Cass. etc) 8 to 10" minimum diameter. I would aim
for a system with less than 30% obstruction by diameter, F12 or longer. The
tube should have good ventilation for the mirror so it is useable during early
evening when the air cools down. Expect to pay more for the tube assembly than
for a Newtonian. If it's cheap, it probably has too many compromises. Look for
a system from a precision builder with a top reputation.

Refractor, 7" to 9" Apo, F8 to F11, or 8" to 12" achromat, F12 or longer. These
scopes will cost the most, although excellent achromats can be gotten at
reasonable prices from builders like D&G Optical. Inch for inch, refractors
will have more light grasp, and in my own experience, an edge on contrast which
is important in making out planetary detail. Achromats will have chromatic
aberration effects that turn some people off but others have learned to ignore.
You can minimize this by use of filters, or perhaps with the introduction of
color correcting lenses such as the Chromacorr (made by Aries) this defect can
be corrected at a reasonable cost. Apochromats solve this problem entirely, but
at a high cost. There are other advantages such as astrophotography that make
Apos the first choice among some amateurs. Be aware, just because a
manufacturer claims to use an ED element, it is not necessarily an Apochomat
with full correction of chromatic aberration. Avoid cheap Apos, rather buy a
good achromat if your budget does not allow a real Apo.

Whatever system you choose, you might want to consider your local viewing
conditions. For planetary, light pollution has zero effect, so you can observe
right from your backyard in a downtown area. The most important thing is the
stability of the air above. The better your seeing i.e. steadiness of the
image, the larger the instrument I would install. The farther south you live,
the larger the scope that will be most effective. If you can only afford a 6"
or 7" instrument, don't despair that you will not see anything. I know some top
planetary amateurs who regularly observe with those apertures and have seen
amazing detail on the planets.

Good luck in your choice.

Roland Christen

[Ron B[ee]]

I've read that a few people said the the shroud would creep down the tube.
I also realized that truss makes the scope very light and thus portable.
I think a tube will be best for *me* because of stray lights from the
neighbors,
just my personal preference and not a generalization.

Ron B[ee]
----------
"Del Johnson" <dela...@san.rr.com> wrote in message
news:BIox6.136796$GV2.34...@typhoon.san.rr.com...

[Del Johnson]

I think that "shroud creep" is a solvable problem. You could even make your
own shroud. A solid tube is going to introduce more problems than it
solves. Balance (in the Portaball) and transportability (for all large
reflectors) to name two. Look how much more Discovery charges for a truss
telescope over a solid tube. People would not pay that much more unless
there was reason for doing so. The truss is the definitely the way to go.

Del Johnson

"Ron B[ee]" <ro...@home.com> wrote in message

news:AYqx6.99479$o7.38...@news1.rdc1.sdca.home.com...

[Michael Spooner]

Great post Roland. Also, no matter what scope one uses, please spend time
discerning what it takes to get the most out of it. I've seen folks take
beautiful scopes and plonk them down on a slab of concrete, point them
across a heat soaked tile roof and then gripe because they can't see
anything. Even a poor to mediocre scope that has been setup to avoid body
heat from the observer, no light paths across warm car hoods, etc. and well
cooled and collimated will outperform the first setup by a wide margin. And
superb optics that are pushing their limit will take one's breath away. Most
folks have never even see the limit of a 6" to 8" class scope on planetary
viewing. Those nights are indeed rare IMHO.

--Mike Spooner

--
Posted from MAIL.DCACCESS.COM [64.212.3.142]
via Mailgate.ORG Server - http://www.Mailgate.ORG

[Ratboy99]

>Also, no matter what scope one uses, please spend time
>discerning what it takes to get the most out of it.

That is an excellent comment. It took me years before I even figured out that
there were things that I could do to make a significant difference in my
scope's performance. As I continue to use the same scopes I get better and
better at tweaking their performance. They have all become increasingly 'works
in progress'. There is a real sense of satisfaction in getting something like
this 'sussed', as well. The great views are all the more meaningful.
rat
~( );>

email: remove 'et' from .com(et) in above email address

[Esmail Bonakdarian]

Chris1011 wrote:
>
Hi

Interesting post, thanks.

> image, the larger the instrument I would install. The farther south you live,

^^^^^^^^^^^^^^^^^^^^^^^^^^^

why would this make a difference? Are you talking about weather?

> the larger the scope that will be most effective. If you can only afford a 6"
> or 7" instrument, don't despair that you will not see anything. I know some top
> planetary amateurs who regularly observe with those apertures and have seen
> amazing detail on the planets.

--
Esmail Bonakdarian - esm...@uiowa.edu - http://www.cs.uiowa.edu/~bonak

[Sjoplinh]

Roland C. writes;

>>
In a Newtonian 8" to 12" with small central obstruction under 20%, very thin
spider, longish F ratio above F6, excellent tube construction with well
ventilated mirror and a decent flotation mirror cell (no mirror glued to

plywood)...<<

Re the mirror cell: Isn't it OK to silicone the mirror to plywood if it's of
"full" thickness? I just finished shellacking and painting the (3.4" ply) cell
for my mirror, which is a 4.25", 0.75" thick. I was planning to attach it with
three blobs of silicone at about 60% radius.

Cheers,

Scott

[Alan]

Us folks in the north often find the planets low in the sky where the seeing
is poor. Mars, for instance, will not get very high in our skies this year.
It will be higher for folks down in the southern part of the US and they are
likely to benefit from better seeing.

Clear skies, Alan

"Esmail Bonakdarian" <esm...@uiowa.edu> wrote in message
news:3AC681C5...@uiowa.edu...

> Chris1011 wrote:
> >
> Hi
>
> Interesting post, thanks.
>
> > image, the larger the instrument I would install. The farther south you
live,
>
^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> why would this make a difference? Are you talking about weather?

> [SNIP]

[Ron B[ee]]

Hi Del,

Umm, sounds like you know a lot of this shroud thing. Suppose if I
were to get an 8" portaball, would a *permanent* shroud be possible
with this scope? I don't plan to travel with the scope.

Thanks,
Ron B[ee]
-----------

"Del Johnson" <dela...@san.rr.com> wrote in message

news:frrx6.136952$GV2.34...@typhoon.san.rr.com...

[Del Johnson]

I don't own a PortaBall but I did design and build the structure for my
reflector. I have encountereed and solved numerous problems, and the shroud
seems like a minor issue. Velcro will probably do the trick.

Del Johnson

"Ron B[ee]" <ro...@home.com> wrote in message

news:%hxx6.100336$o7.39...@news1.rdc1.sdca.home.com...

[Dan Chaffee]

On 01 Apr 2001 01:57:05 GMT, sjop...@aol.com (Sjoplinh) wrote:

>Re the mirror cell: Isn't it OK to silicone the mirror to plywood if it's of
>"full" thickness? I just finished shellacking and painting the (3.4" ply) cell
>for my mirror, which is a 4.25", 0.75" thick. I was planning to attach it with
>three blobs of silicone at about 60% radius.

You are taking your chances; it may be stable enough, or it may
not, depending on that particular piece of wood. It takes surprisingly
little force to distort even a small full thickness substrate. With
direct boundage to plywood everything may be fine until you
get a day of higher humidity and suddenly the images are
astigmatic.

D Chaffee

[Valery Deryuzhin]

Roland Christen wrote:

>or 8" to 12" achromat,

>F12 or longer. Thesescopes will cost the most, although excellent achromats can
>be gotten atreasonable prices from builders like D&G Optical. Inch for inch,
>refractorswill have more light grasp, and in my own experience, an edge on
>contrast whichis important in making out planetary detail. Achromats will have
>chromaticaberration effects that turn some people off but others have learned to
>ignore.You can minimize this by use of filters, or perhaps with the introduction
>ofcolor correcting lenses such as the Chromacorr (made by Aries) this defect can

>be corrected at a reasonable cost. Apochromats solve this problem entirely, but
>at a high cost.

 

 

Just for info:

 

I can add to this, that due to very high interest to a so called "converted apos"

(achromats with pre-installed color corrector like Chromacor) ,  we already

begin  five  8" F/8  "converted  apos"  .  They will have excellent correction

within 470 - 620nm  - no spherochromatism at all.   Each scope will be specially

matched with its larger than normally (actually 40mm) Chromacor to eliminate

spherical aberration. This will be fully optimized  visual scope,  purposed for

planetary and other  high resolution works. 

 

 

Valery Deryuzhin 

ARIES

 

 

 

 

 

 

 

 

 

[Dan Chaffee]

On Sat, 31 Mar 2001 20:51:23 GMT, "Del Johnson" <dela...@san.rr.com>
wrote:

>I think that "shroud creep" is a solvable problem. You could even make your
>own shroud. A solid tube is going to introduce more problems than it
>solves. Balance (in the Portaball) and transportability (for all large
>reflectors) to name two. Look how much more Discovery charges for a truss
>telescope over a solid tube. People would not pay that much more unless
>there was reason for doing so. The truss is the definitely the way to go.

I have done extensive experimentation with solid tubes, tubes with
vents, and truss variants and _generally_tend to agree with this.
Actually, the best solution I have arrived at is a carefully carved up
tube that protects the optical path from body heat with an expanse of
tube intact at the upper end, and yet enough overall openess that
I rarely see tube currents. I don't have a web page, but will
email a jpg to anyone curious about my particular design. This
scope, a 9.65" full-thickness f/7.4 newtonian cools VERY fast and
images are rarely improved upon by leaving a fan on longer than 40
minutes for initial cool down.
Now then, I say 'generally' because let's not forget that some of the
best planetary images out there, such as Parker, Di Sciullo, et al
are fetched with solid tube newtonians--so it CAN be done in the
right environment with the right modifications and materials to
dispense with thermal issues.
On another note, observers that freaquent star parties
with their bare bones dobs often sweat bullits when so and so with
that fat cup of Pepsi gets a little too close to the merchandise,
so well fitting shrouds are a wise accessory.

D Chaffee

[Jon Isaacs]

>I think that "shroud creep" is a solvable problem. You could even make your
>own shroud. A solid tube is going to introduce more problems than it
>solves.

As the fellow said, he prefers a Solid tube. While it is true that truss tubes
have some advantages, it is also true they have some disadvantages, you named
the big one, COST. If one is comfortable with a solid tube DOB, and is able to
transport it or use it only in a fixed location, the added cost may buy
nothing.

Also there are those of us who like the ease of setup of a solid tube DOB.

jon isaacs

[mark d. doiron]

"Jon Isaacs" <joni...@aol.com> wrote in message
news:20010401084513...@ng-fz1.aol.com...

snip

> If one is comfortable with a solid
> tube DOB, and is able to
> transport it or use it only in a fixed
> location, the added cost may buy
> nothing.
>
> Also there are those of us who like the
> ease of setup of a solid tube DOB.

Jon--

since the original poster was considering very large apo's, cost doesn't
seem to be a significant issue. regarding the ease of setup up a solid
tube dob: the StarMaster el series provide similar ease of setup
features to a solid tube dob. the new 14.5" StarMaster also has this
"el feature" in that the trusses and secondary cage can be left
assembled as one unit, allowing the owner to split the scope into two
pieces for transport. more info and pic's at:

http://www.starmastertelescopes.com/html/new14.htm

what does the extra money then buy? well, the option in the future to
transport the scope--on a camping trip, to a star party, to dark skies
for a particular viewing challenge, whatever may be unforeseeable today,
but desired tomorrow. on top of that, the 14.5" StarMaster is offered
with goto and tracking--many of us would consider motorized tracking as
a necessary feature of the "best planetary scope", which is the subject
of this thread. :-)

[Alan]

Dave,

To me, it seems rather odd that large APOs are generally not considered
portable, yet large Dobs certainly have parts that are much heavier and
bulkier than an 8" APO and many people think nothing of hauling a 25" Dob
out to a dark sky site.

Generally, I consider a telescope and mount that fits in our mini-van, has
no parts over about 60 pounds, and can be comforably set up by myself in
about 20 minutes to be "portable." When you get into scopes that take two
people to handle or require a large number of tools for set up then I lose
interest.

Clear skies, Alan

"Dave Novoselsky" <DN...@ix.netcom.com> wrote in message
news:8Bcx6.17463$4D.3...@typhoon.mw.mediaone.net...
> [SNIP]

> I can speak from first hand experience since I have an 8" APO, a TMB 203
> f/9. It is superb, but I waited a year for it, and like any large APO,
set

> up and take down is a bear. Once up, the work is worth it, [SNIP]

[Reef1969]

Alan, it sounds like the TEC 10" F20 meets those requirements. I would put
that scope up against any mentioned, and I am sure it would do well. You also
dont have to view standing up, which is really important to me.

Richard

[Alan]

Richard,

It probably would, but I am not in the market for anything at the moment.
Perhaps when I retire I will treat myself to something, but that is still
about five years off.

Clear skies, Alan

"Reef1969" <reef...@aol.com> wrote in message
news:20010401104911...@ng-co1.aol.com...
> Alan, it sounds like the TEC 10" F20 meets those requirements. [snip]

[Jan Owen]

OK, Valery,

 

So tell us more about this scope, and what it's price range will be...

""Valery Deryuzhin"" <ar...@selena.kherson.ua> wrote in message news:004a01c0ba7a$91e42b80$3c60dcc1@--------...

[Dave Novoselsky]

Large Dobs break down into multiple parts, and the heaviest can be 'wheeled'
around. Can't 'break down' a large APO. The 8" TMB is a problem for me
only as I am 5' 10" with a bad back. Moving it out and picking it up, etc,
isn't so much the problem as hoisting it into the saddle plate. The
adjustable height pier will cure that, but the roll off will make it even
better. I am sure you have noted the same thing with you own 8" APO. Like
you, I will take it to observing events using the normal tripod for the HGM
200 mount. I am sure I can garner a little help getting it set up. <g>
All in all, I remain a big fan of big APOS. Dave
"Alan" <Sue_and_A...@email.msn.com> wrote in message
news:eHZVZIruAHA.355@cpmsnbbsa07...

[CHASLX200]

>Subject: Re: Best planetary scope? 8" APO?
>From: "Alan" Sue_and_A...@email.msn.com
>Date: 3/31/01 9:53 PM Eastern Daylight Time
>Message-id: <eiDzJ9kuAHA.369@cpmsnbbsa09>

>
>Us folks in the north often find the planets low in the sky where the seeing
>is poor. Mars, for instance, will not get very high in our skies this year.
>It will be higher for folks down in the southern part of the US and they are
>likely to benefit from better seeing.
>
>Clear skies, Alan

>********************************
Mars should be plenty high for me, at Lat 27.8 north. Can't wait to see Mars
in my 14.5" Starmaster, at over 1000x!!!

Chas P.

[Bill Becker]

Hi Ron B[ee],

I suspect it will probably be an f/10, optimized for planetary
observing.

[Bill Becker]

Hi Dave,

If I'm ever around you and your 8"er, you can count on me for help. ;^)
With the fine contrast of your TMB, I'd love to give Sirius a look see
to get a look at the pup.

Best regards,
Bill

[Sjoplinh]

Me: >>...I just finished shellacking and painting the (3.4" ply) cell

>for my mirror, which is a 4.25", 0.75" thick. I was planning to attach it
with
>three blobs of silicone at about 60% radius.

Dan:

>>You are taking your chances; it may be stable enough, or it may
not, depending on that particular piece of wood. It takes surprisingly
little force to distort even a small full thickness substrate. With
direct boundage to plywood everything may be fine until you
get a day of higher humidity and suddenly the images are
astigmatic.<<

Well, now I'm a bit worried!
I should have hit it with additional coats of shellac, or "melted paraffin"
(supposed to be best protectant against humidity changes).
I guess I'll give it some more coats of flat black, and make sure the
silicone pads are thick enough (but not too thick), and hope for the best.
Thanks for the reply.

Scott

[Dave Novoselsky]

You are always welcome. Dave

"Bill Becker" <bb...@rmisp.com> wrote in message

news:3AC75D45...@rmisp.com...

[Reef1969]

I would like to treat myself to the TEC, but my better half?, will treat me to
a butt whooping if I do. I will have to wait awhile.

Richard

[Valery Deryuzhin]

Jan Owen wrote:

 

 

OK, Valery,

 

So tell us more about this scope, and what it's price range will be...

 

 

Jan,

 

This telescope will be 8" F/8 achromat  with  Chromacor D=40mm  pre-installed.

This will allow to have excellent color correction within 470 - 620nm spectral range

without any spherochromatism - in this spectral range this scope will deliver the most

sharp image - sharper than standard apos which always have some amount of sphero-

chromatism. 

Premanent Chromacor installation will allow to match an objective with its corrector

very precisely - we will correct spherical aberration within 1/20 wave P-V .  Because

a spherochromatism is absent,  such correction will be valid for wide enough spectral

range from blue (470nm) to light red (620nm) .  MTF (contrast)  function value will exeed

standard apos because they are not same good corrected (spherically) within this spectral

range. 

A color correction will somewhat degrade out of this range,  but for most interesting objects

like moon, Jupiter, Saturn, Mars,  Mercury  this scope will deliver a color-free images.

Of course, Venus and brighetst white and blue stars will show some amount of deep violet.

 

For amateurs, who like to observe with binoviewers we will add a correction lens which

always needed for coorrection of bino's own spherical and schromatic residual aberration

(for fast systems F/D< 12) .  If this lens is in any case needed, why not add anothet task for

its role - to correct colors even better?  This correction lens for our "converted apos" will be

made with one Chromacor's unique glass and will improve a color correction even more.

 

At this moment we consider to use a BORG 3" or 4" focusers in these scopes.  They will be

also very light weight.  We will save a weight in any part.  We hope to make these scopes

transportable and suitable for viusal use om G-11 and CCD-photo-visual for mounts like AP900.

This scope will have excellent field correction (flat field) enough for largest amateur  CCDs

and 35mm film photography.

 

High transmittion coatings on all surfaces will warranty a minimal light loss.

 

These scopes will be within 10K and will never require any service.   As I wrote, we already

begin to make optics for first 5 samples.  They will be ready before end of September.

May be sooner.

 

 

Valery Deryuzhin.

 

 

[Valery Deryuzhin]

Zane wrote:

>You might check out Excelsior Optics' 10 inch planetary Newtonian.  Ihaven't
>seen one but he gets unbelievable planetary images.  If I wereafter a planetary
>scope I'd look at one before I bought a refractor in the8 inch size range. 
>(There are some good reasons why there aren't many thatlarge around these days.)
>

>Zane

 

 

Zane,

 

We will try to correct this situation on the market .  As I wrote,  soon we will

introduce an 8" F/8 converted apo scope. This will be a good alternative scope

for  $$$$$  true 8" apos.  We _already _ see a high demand on this scope.

Upon special order we can make even 9" F/7.2 converted apo.

Slightest compromise in a marginal spectral parts (for human eye) will be

quite acceptable trade-off for a good prortability,  excellent correction within

true visual spectrum and much cheaper price + short delivery.

 

Valery Deryuzhin

ARIES.

 

[Valery Deryuzhin]

I also think that 10" or even 12" MCT with small central obstruction

like c.o. <25%  will be a nice choice too, especially if an advanced

cooling  system is installed.

 

 

Valery Deryuzhin

ARIES.

[Bill Foley]

Valery,
This sounds great, and we applaud your work in this area. One thing,
while selecting components for their weight, do remember that it is nice
if the BALANCE of the OTA is such that more weight is away from the
front so the focuser is high enough to be comfortable even near zenith.
Thanks again for your good works and results.
--
Best Wishes,

Bill Foley

P.S. Ignore the reply-to address, it is to foil spammers.

[Alan]

Dave,

That was, IMHO, the crux of the assembly process. I solved it with the
proper ladder. The tube is lifted up onto a small jig attached to the
ladder. The top step of the ladder is a fairly wide platform, and from
there it is easy to lift the tube up into the saddle. Neither of the lifts
is much above shoulder height. I do think my ota weighs a bit less than
yours (about 55 pounds). The ladder also makes it very easy to put the RA
assembly on the pier and attach the dec assembly.

But it is not something I would want to do if I had back problems.

Clear skies, Alan

"Dave Novoselsky" <DN...@ix.netcom.com> wrote in message

news:BEIx6.20203$4D.4...@typhoon.mw.mediaone.net...
> [SNIP] The 8" TMB is a problem for me

> only as I am 5' 10" with a bad back. Moving it out and picking it up,
etc,

> isn't so much the problem as hoisting it into the saddle plate. [SNIP]

[Del Johnson]

Don't wax the wood or the adhesive will fail!

You should not bond the mirror at all. Let gravity hold the mirror in place
and use non-contact safety clips in case the tube is inverted. Don't worry
about the tiny little obstruction of the clips! This means nothing at all
to the view quality. What will ruin your images is the mirror being
stressed by the adhesive. A compromise would be to use one blob at the
center and plus a couple more free contact supports (plus non-contact safety
clips). One point of adhesion will not stress the mirror if the substrate
expands.

Del Johnson

"Sjoplinh" <sjop...@aol.com> wrote in message
news:20010401131257...@ng-mh1.aol.com...

[Del Johnson]

People eat food or they look through my telescope, but they don't do both at
the same time!

Del Johnson

"Dan Chaffee" <dcha...@gvi.net> wrote in message >

[Del Johnson]

He also said that he prefers refractors, so this is all moot. :-)

Solid tubes are convenient for smaller reflectors, but are very clumsy above
10 inches of aperture.

Del Johnson

"Jon Isaacs" <joni...@aol.com> wrote in message
news:20010401084513...@ng-fz1.aol.com...

[Del Johnson]

There are two reasons for this:

1. The refractor is generally a lot longer for the same aperture and
generally does not dissassemble to fit in an automobile. I only need the
trunk of a sedan to transport my 12" reflector for visual observing. No van
or SUV required.

2. The refractor must be lifted quite a bit higher when mounted. The
center of gravity of a typical large Dobsonian is typically less than two
feet off the ground.

Del Johnson

"Alan" <Sue_and_A...@email.msn.com> wrote in message
news:eHZVZIruAHA.355@cpmsnbbsa07...

[Travis Morien]

On Sat, 31 Mar 2001 20:51:23 GMT, Del Johnson said...

>
>I think that "shroud creep" is a solvable problem. You could even make your
>own shroud. A solid tube is going to introduce more problems than it

>solves. Balance (in the Portaball) and transportability (for all large
>reflectors) to name two. Look how much more Discovery charges for a truss
>telescope over a solid tube. People would not pay that much more unless
>there was reason for doing so. The truss is the definitely the way to go.

Or you could do what I did while building my last newtonian, have modular
componants that can be transferred from one mount to the next. In my case I
have a heavy offset cradle mount for home, the tube is a box made from oregon
wood with thin veneer as a cover. The bottom of the tube can be taken off,
which takes with it the mirror, the cell and what you might call the "cap" of
the tube.. The secondary is removable in its cell from the spider (standard
spider design, undo the bolt and off the mirror comes.

The optics is then readily put into the transportible, which is a fairly
conventional truss dob. Of course it needs collimation all over again, but I
find the setup satisfactory, I can stick a tarp over the cradle mount and lug
the tube inside. The dob mount is nice because the whole thing is *very* light.
It's an 8" f6 in case anyone is wondering. I have several projects incomplete,
I seem to be unable to find the time to finish off mirrors I start (though I do
have time to start them, apparantly!)

I know very little about refractors and have no knowledge of who makes good
ones. The Meade unit looked great in the pamphlets and the whole computer drive
looks impressive, but after the horror stories I've now read I think I'll join
the waiting list at AP. Do they require a deposit?? I recently landed a job
that pays quite well, and for the first time in my life I can actually afford
something as outrageous as a big APO, *with* a box of Naglers (or would that be
chest of Naglers, given the size of each one of them?) I'd consider an
unobstructed reflector and even have the pyrex blanks for a Yolo I've
designed.... with my new job I have no hope of ever finding the time even to
finish the optics on my 6" RFT, let alone a 12" Yolo, however I do have
money.... hence the APO inquiry.

Does Astro Physics look like the one to get? Money isn't really the issue, I'm
getting this thing in lieu of a new car!

Travis

[William]

Travis,

From my readings here and elsewhere and e-mails from many folks far more
knowledgeable than me, I believe that Astro-Physics is the way to go if you
want a really great 5" or 6" refractor and don't mind waiting 3-4 years
(unless, of course, you can find a used one somewhere).

Although Takahashi makes great scopes, they are outrageously expensive and
probably not quite the quality of an A-P. TMB refractors are quite
expensive, too (see Astronomics' website), but, beyond that, I have not
heard anything really good or bad about TMB's.

My strategy has been to buy an Orion/Vixen VX102-FL 4" fluorite to play with
until the day A-P sells me a 6". (The Vixen fluorite is rated very highly
by most everyone.) The bottom line for me: I simply cannot go wrong with
A-P's quality and price, and I'm willing to wait.

William

"Travis Morien" <travis...@yahoo.unspam.com> wrote in message

news:pALx6.3238$bY4....@www.newsranger.com...

[John Shakespeare]

Hi Del,

Avoiding glue is an important point, especially if the telescope is to be
exposed to large temperature ranges. My 10" was fine at +10C and at 0C, but at
-15C some astigmatism became evident, and at -20C to -25C was really
objectionable. Defocussing Jupiter at -20C split its image into three as
vertices of an equilateral triangle, just as if a Hartman mask was being used.
The cause was the glue binding the mirror to the three metal ribs of the mirror
cell. Since the metal's coefficient of thermal expansion differs from that of
the glass mirror, thermal contraction of the cell was inducing radial stresses
in the mirror along the three ribs. This meant that, even in focus, the image
was softened.

The cure was to remove the glue. The mirror cell already had three mirror clips
which were adequate for holding the mirror. I had initially suspected that they
were pinching the mirror and were the cause of the problem, but it turned out to
be the glue instead.

Best Regards,
John.

[Dave Novoselsky]

Thank you for the information, Alan. Dave

"Alan" <Sue_and_A...@email.msn.com> wrote in message

news:OxUxy2tuAHA.369@cpmsnbbsa09...

[Ratboy99]

So how do you mount an 8" F15 Achromat?

I haven't seen an appropriate (affordable and portable) mount, unless maybe
that Mountain Instruments 250 would work.
.
I'll bet one of those 8" D&G's would make a killer planetary scope.

rat
~( );>

email: remove 'et' from .com(et) in above email address

[Dave Novoselsky]

No way. I spoke to Larry, the owner of MI and one of the nicest, most
honest and knowledgable guys in the business. He thought the issue was the
length of an 8" f/9, and said that wouldn't work. So I doubt if an 8" f/15
would come any closer. I suppose the way to go would be to contact Joe
Natasi at Parallax, and order one of his 300 series mounts, but I recall
they start at about 21K. Or, you could build one. Dave
"Ratboy99" <ratb...@aol.comet> wrote in message
news:20010401201417...@ng-fx1.aol.com...

[Sjoplinh]

Del writes;

>>Don't wax the wood or the adhesive will fail!<<

Thanks; I stayed with shellac and paint, and there are deep drilled holes to
help the silicone blobs.

>>You should not bond the mirror at all. Let gravity hold the mirror in place

and use non-contact safety clips in case the tube is inverted...<<

I appreciate the advice.
Let me point out;
-- The cell is 3/4" plywood, well dried, painted, etc.;
-- The mirror is full thickness (3/4") and only 4.25" dia.;
-- The silicone pads will be at only about 0.6 radius, and "optimally" thick;
-- The temp. / expansion of wood, at least along the grain, is less than most
metals, and much less than most plastics. (This is temp only and doesn't take
into account moisture.)
-- Silicone is not epoxy. Check it out. It's got a bit of "give".

I'd think that flotation brings its own problems. Side / bottom supports will
either have slop (as will Silicone pads, I guess, but likely less?) or pinch
the mirror. Or both, depending. Mine will be alt-az, with less a problem
there, but still...

I'll obviously have to look into this more. I'll probably set it up as
planned, and if I detect any hint of astig or less than great images (it's a
great mirror, IMHO), I can always remount it.

Thanks again to all for the very welcome advice.

Best,

Scott

[William R. Meyers]

Hi, Roland,
A classy answer from a classy guy.
Bill Meyers

Chris1011 wrote:

> >>but does anyone recommend another instrument,>>
>
> You will get dozens of different opinions on what is best, but I will tell you
> that for any given type of scope configuration, be it Newtonian, Cassegrain or
> Refractor, there will be excellent, just acceptable and rather poor examples
> for each type. No one type can lay claim to being the absolute best. If you are
> looking for an outstanding planetary scope you should consider the following:
>
> In a Newtonian 8" to 12" with small central obstruction under 20%, very thin
> spider, longish F ratio above F6, excellent tube construction with well
> ventilated mirror and a decent flotation mirror cell (no mirror glued to
> plywood). Shorter F ratios require that the object be exactly centered in the
> field to avoid comatic aberrations. Also, the shorter the mirror, the more you
> will have to fiddle with the collimation. The mirror should have the best
> coating you can afford, avoid cheap coatings that lose contrast over time. Get
> a coating that you can clean without introducing pinholes. Add to that a smooth
> functioning focuser and you will have a very effective planetary instrument.
>
> In a Cassegrain (this includes open and closed tube systems, Dall Kirkam,
> Maksutov, classical, Schmidt Cass. etc) 8 to 10" minimum diameter. I would aim
> for a system with less than 30% obstruction by diameter, F12 or longer. The
> tube should have good ventilation for the mirror so it is useable during early
> evening when the air cools down. Expect to pay more for the tube assembly than
> for a Newtonian. If it's cheap, it probably has too many compromises. Look for
> a system from a precision builder with a top reputation.
>
> Refractor, 7" to 9" Apo, F8 to F11, or 8" to 12" achromat, F12 or longer. These

> scopes will cost the most, although excellent achromats can be gotten at
> reasonable prices from builders like D&G Optical. Inch for inch, refractors
> will have more light grasp, and in my own experience, an edge on contrast which
> is important in making out planetary detail. Achromats will have chromatic
> aberration effects that turn some people off but others have learned to ignore.
> You can minimize this by use of filters, or perhaps with the introduction of
> color correcting lenses such as the Chromacorr (made by Aries) this defect can
> be corrected at a reasonable cost. Apochromats solve this problem entirely, but

> at a high cost. There are other advantages such as astrophotography that make
> Apos the first choice among some amateurs. Be aware, just because a
> manufacturer claims to use an ED element, it is not necessarily an Apochomat
> with full correction of chromatic aberration. Avoid cheap Apos, rather buy a
> good achromat if your budget does not allow a real Apo.
>
> Whatever system you choose, you might want to consider your local viewing
> conditions. For planetary, light pollution has zero effect, so you can observe
> right from your backyard in a downtown area. The most important thing is the
> stability of the air above. The better your seeing i.e. steadiness of the
> image, the larger the instrument I would install. The farther south you live,
> the larger the scope that will be most effective. If you can only afford a 6"
> or 7" instrument, don't despair that you will not see anything. I know some top
> planetary amateurs who regularly observe with those apertures and have seen
> amazing detail on the planets.
>
> Good luck in your choice.
>
> Roland Christen

[William R. Meyers]

Hi,
This whole thread is an unusually helpful non-combative discussion among people
with very different preferences.I went on vacation for a few days and everything
is different. What happened to you guys? Are you alright?:-)
Bill Meyers

[Del Johnson]

I know that you are using better materials, but I recently replaced some
cheap particle boards in a Celestron Starhopper that had swelled 50% due to
moisture uptake!

There is no slop is a flotation cell as the contacts assume the preferred
profile of the mirror's backside with equal loading. This is in fact why
the flotation cell works so well. The Dobsonian has an advantage with
regard to side supports as only one side of the mirror is downward (for the
most part). One simply has a rigid support along the lower perimeter and a
soft support on the upper perimeter. I am not an advocate of slings as they
can transfer stress to the mirror if there is any stretch at all.

Del Johnson

"Sjoplinh" <sjop...@aol.com> wrote in message

news:20010401210922...@ng-mg1.aol.com...

[Dan Chaffee]

On 01 Apr 2001 17:12:57 GMT, sjop...@aol.com (Sjoplinh) wrote:

>
>Well, now I'm a bit worried!
>I should have hit it with additional coats of shellac, or "melted paraffin"
>(supposed to be best protectant against humidity changes).
> I guess I'll give it some more coats of flat black, and make sure the
>silicone pads are thick enough (but not too thick), and hope for the best.

Many amateurs have successfully mounted their mirrors
(considerably larger than 4.25") in this way and had no
problems. But, better safe than sorry in my opinion.

One solution tho the 'clip problem' is to make a ring, or
annulus that holds the mirror by overlapping the outer
edge by a couple of mm (curing TDE at no extra charge
as well), and mounting it so that the mirror is slighly loose
and not bound firmly. I have found this to be an excellent
way of holding a mirror on a floatation system.

Dan

[Richard Anderson]

From a practical standpoint, you could replace the current cell, tube
and focuser and get the weight of the 8" down to a more manageable
one. Meade's 7" ED although ridiculed alot is a pretty light OTA
and there is no reason this couldn't be done for the TMB.
IMO, the Russians/Germans need to consider the lack of utility of
those massive tubes they make as the bulk is not needed.
To make scopes lighter, I've even seen people machine down
cells and focusers from the outside just to shave a couple lbs.
I saw Markus's 12" Coude design and it also looked massively
overbuilt for it's job. This may have some benefit in an observatory,
but not for any portable use. I figure the lens set in the 8" TMB
is around 10lbs or so. The whole OTA could be fabricated
that wouldn't be more than 35lbs which is easily handled.
-Rich

On Sun, 01 Apr 2001 16:26:09 GMT, "Dave Novoselsky"
<DN...@ix.netcom.com> wrote:

>Large Dobs break down into multiple parts, and the heaviest can be 'wheeled'

>around. Can't 'break down' a large APO. The 8" TMB is a problem for me

>only as I am 5' 10" with a bad back. Moving it out and picking it up, etc,

>isn't so much the problem as hoisting it into the saddle plate. The
>adjustable height pier will cure that, but the roll off will make it even
>better. I am sure you have noted the same thing with you own 8" APO. Like
>you, I will take it to observing events using the normal tripod for the HGM
>200 mount. I am sure I can garner a little help getting it set up. <g>

>All in all, I remain a big fan of big APOS. Dave

>"Alan" <Sue_and_A...@email.msn.com> wrote in message

>news:eHZVZIruAHA.355@cpmsnbbsa07...
>> Dave,
>>
>> To me, it seems rather odd that large APOs are generally not considered
>> portable, yet large Dobs certainly have parts that are much heavier and
>> bulkier than an 8" APO and many people think nothing of hauling a 25" Dob
>> out to a dark sky site.
>>
>> Generally, I consider a telescope and mount that fits in our mini-van, has
>> no parts over about 60 pounds, and can be comforably set up by myself in
>> about 20 minutes to be "portable." When you get into scopes that take two
>> people to handle or require a large number of tools for set up then I lose
>> interest.
>>

>> Clear skies, Alan
>>
>> "Dave Novoselsky" <DN...@ix.netcom.com> wrote in message

[Richard Anderson]

You did the right thing and you have the patience to wait.
You also have another high quality refractor to tide you
over, which at least means you don't suspend 3-4 years of
observing with your own equipment to wait for the AP.
The good thing about higher quality scopes is that the "rent" is
cheap in that you can re-sell them (although you might still keep
the 4" FL after you get the big 6" AP) near their new value.
Image if we could do that with televisions!
-Rich

On Sun, 01 Apr 2001 20:04:22 GMT, "William" <willi...@earthlink.net>
wrote:

[Ron B[ee]]

Thank Bill for the info.

Wow, so the tube length would probably be 70", high taller for
a short guy like me, sigh.... The one question that comes to my mine:
the refractor people have figured out how to build an excellent
short focal ratio instrument (AP, Tak, and TV - I recalled when
I was in school that most refractors were f/15!). I wonder why
the Newtonian designers haven't done so. ( I've read all about
the problems with f/5 and f/4 Newtonian - lots of coma and huge
secondary obstruction). Just thinking out loud.

Ron B[ee]
-----------

"Bill Becker" <bb...@rmisp.com> wrote in message

news:3AC75C0B...@rmisp.com...
> Hi Ron B[ee],
>
> I suspect it will probably be an f/10, optimized for planetary
> observing.
>
> Best regards,
> Bill
>
> "Ron B[ee]" wrote:
> >
> > Thanks Bill for the info. 7" sounds even better providing it's an f/7
(or
> > f/5.6
> > like the classic Starmaster); I can't take anything more than 48" long
:-(.
> > If so, I'd definitely *cut in line* to get in front of you :-). It's
also a
> > shame
> > that Starmaster doesn't make the Classic 7" anymore; I bet the wait
would
> > be even longer than for an AP. I think there's a market for a small,
light,
> > and
> > somewhat portable Newtonian but with *exquisite* APO like quality.
> > Although,
> > I'm bias toward a refractor and personally never like a Newtonian, this
is
> > one great exception. Someone told me about the PortaBall, but I don't
> > like the truss concept and the shroud works poorly.
> >
> > Do you know when Maurizio is planning to make it? If very soon, I can
> > junk my current plan for a new scope and wait for his.
> >
> > Ron B[ee]
> > -----------

> > "Bill Becker" <bb...@rmisp.com> wrote in message

> > news:3AC5569C...@rmisp.com...
> > > Hi Ron B[ee],
> > >
> > > Would you believe a 7"? Maurizio is seriously considering this
aperture
> > > for his next project.(he used to make 6"ers...not sure of the focal
> > > ratio)
> > > Would you like to stand in line behind me? <g>
> > >
> > > Best regards,
> > > Bill
> > >
> > > "Ron B[ee]" wrote:
> > > >
> > > > Although, I'm not seen one nor use one, I think this is the
> > > > best planetary scope, IMHO. Go to this link.
> > > > http://www.excelsioroptics.com/
> > > > Also, go the CCD image place. I think in the case a picture
> > > > is worth 1000 words :-). I've never seen such pictures taken
> > > > with amateur scopes.
> > > >
> > > > Ron B[ee]
> > > > PS Now, how I wish they would make a 6" f/8 version for
> > > > a small guy like me.
> > > > ------------

> > > > "Travis Morien" <travis...@yahoo.unspam.com> wrote in message

> > > > news:Ic6x6.1950$bY4....@www.newsranger.com...
> > > > > Hey guys,
> > > > >
> > > > > I'm soon to be in a position to buy a medium to large sized
> > apochromatic
> > > > > refractor, I am looking at the Meade 7" ED apo. I have heard
great
> > things
> > > > about
> > > > > them, but does anyone recommend another instrument, like an Astro
> > Physics
> > > > > perhaps? Something in 8" would be good, but Meade don't make
them.

[Ron B[ee]]

Hi Alan,

I believe it's because the Dobs sits so low on the ground and the
refractor sits much higher on a pier. Thus, the 8" APO would
"look" very intimidating, but awe-inspiring.

Ron B[ee]
-----------

[mark d. doiron]

"Del Johnson" <dela...@san.rr.com> wrote in message
news:JiLx6.138430$GV2.35...@typhoon.san.rr.com...

> He also said that he prefers refractors, so this is all moot. :-)

Del--

well, i brought up the possibility of a large, high quality dob because
he asked if there's another instrument that he should be considering.
many folks summarily dismiss these as not the best planetary scope, and
i wanted to introduce that for his consideration. even if he does
prefer refractors (a point i don't find in the original post), other
readers may be interested in the fact that there are a few dob's that
can give a good refractor a run for the money.

clear, dark skies--

mark d.

[CHASLX200]

>Subject: Re: Best planetary scope? 8" APO?
>From: "Dave Novoselsky" DN...@ix.netcom.com
>Date: 4/1/01 8:31 PM Eastern Daylight Time
>Message-id: <XLPx6.20447$4D.4...@typhoon.mw.mediaone.net>

>
>No way. I spoke to Larry, the owner of MI and one of the nicest, most
>honest and knowledgable guys in the business. He thought the issue was the
>length of an 8" f/9, and said that wouldn't work. So I doubt if an 8" f/15
>would come any closer. I suppose the way to go would be to contact Joe
>Natasi at Parallax, and order one of his 300 series mounts, but I recall
>they start at about 21K. Or, you could build one. Dave

**********************************
The old Cave 60mm Shaft mount may hold a 8" F15, also Parks makes a huge 60mm
shaft EQ- mount, for around $7000, it will hold a 20" Newt!!!

Chas P.

[mark d. doiron]

"Ron B[ee]" <ro...@home.com> wrote in message
news:LnWx6.105750$o7.41...@news1.rdc1.sdca.home.com...

snip

> I've read all about the problems with f/5 and
> f/4 Newtonian - lots of coma and huge
> secondary obstruction). Just thinking out loud.

snip

Ron--

i think that you're more or less correct about some of the less
expensive, poorly designed newt's. however, coma (by using a paracorr)
and secondary size are moot on the high quality dob's that are being
mentioned as possible "best planetary scope" in this thread. further,
since it is planetary performance were discussing, the use of
coma-producing widefield ep's may be avoidable, making the paracorr a
non-issue. in that case, tracking on the scope would be beneficial.
that is available with a dob with either an eq platform, or with the
goto system that's available on the larger (14.5" and up) StarMasters.

[WHALEN44]

Hi Scott,

Another possible problem using wood is that it might keep the mirror from
cooling quickly, as most heat is lost through the back of the mirror.

Richard Whalen
whal...@aol.com

"Time spent observing the heavens is not deducted from your lifespan"

[Sjoplinh]

Del wrote;

>>I know that you are using better materials, but I recently replaced some
cheap particle boards in a Celestron Starhopper that had swelled 50% due to
moisture uptake!<<

Ouch!!

>>There is no slop is a flotation cell as the contacts assume the preferred
profile of the mirror's backside with equal loading. This is in fact why
the flotation cell works so well. The Dobsonian has an advantage with
regard to side supports as only one side of the mirror is downward (for the
most part). One simply has a rigid support along the lower perimeter and a
soft support on the upper perimeter. I am not an advocate of slings as they
can transfer stress to the mirror if there is any stretch at all.<<

I understand the free - floating main supports, and I see how silicone on wood
could maybe twist the mirror if the wood warps.
But I need to study the methods of side / bottom support. I don't want the
mirror pinched, and I don't want to have to recollimate often either.

This part of ATM is far more difficult for me than making the mirror!

Scott

[Sjoplinh]

Richard wrote;

>>
Another possible problem using wood is that it might keep the mirror from
cooling quickly, as most heat is lost through the back of the mirror.<<

Thanks. I've got one huge and several small holes drilled in the back plate,
and several small / medium ones in the front plate. Not nearly as open as a
modern 3 rib Aluminum cell, but should be OK with a fan.

This (cooling through back of mirror) brings up another question. One well
known manufacturer polishes the backs of the primaries on his Maks. Supposedly
lets the IR out more easily.
OTOH, if the back is rough - medium ground, it will have more surface area.
Which will cool faster?

Scott

[Sjoplinh]

Bill wrote;

>>
Hi,
This whole thread is an unusually helpful non-combative discussion among people
with very different preferences.I went on vacation for a few days and
everything
is different. What happened to you guys? Are you alright?:-) <<

There's enough of that junk in the "real" world, so we can do without here.
;-)

Scott

[Zane]

sjop...@aol.com (Sjoplinh) wrote:

(snip)

>This (cooling through back of mirror) brings up another question. One well
>known manufacturer polishes the backs of the primaries on his Maks. Supposedly
>lets the IR out more easily.
>OTOH, if the back is rough - medium ground, it will have more surface area.
>Which will cool faster?

I don't think there's any difference, theoretically. Neglecting
absorption, there's significant total internal reflection in both cases.
It appears to me that the added surface area of the rough surface is
cancelled by the added total internal reflection and the fact that adjacent
"bumps" re-absorb some of the emitted radiation. This is using
approximations to the shape of the rough surface.

I would be interested to hear of any more-detailed calculations from
anyone, as I have no particular attachment to this conclusion.

Zane

[WHALEN44]

Hi Scott,

I never have tested this, though I would think the rough back/more surface area
should cool faster. Maybe RC could explain the theory behind the polish. I
could see polishing the back of a mirror for other reasons, put not faster
cooldown. I guess I'm missing something here :-)

>One well known manufacturer polishes the backs of the primaries on his Maks.
Supposedly lets the IR out more easily.
OTOH, if the back is rough - medium ground, it will have more surface area.
>Which will cool faster?
>
>Scott

[Ratboy99]

>>One well known manufacturer polishes the backs of the primaries on his Maks.
>Supposedly lets the IR out more easily.
>OTOH, if the back is rough - medium ground, it will have more surface area.
>>Which will cool faster?
>>
>>Scott

I seriously doubt whether it will make any difference at all on a 4.25" mirror.

[Sjoplinh]

Richard writes;

>>Hi Scott,
I never have tested this, though I would think the rough back/more surface area
should cool faster. Maybe RC could explain the theory behind the polish. I
could see polishing the back of a mirror for other reasons, put not faster
cooldown. I guess I'm missing something here :-) <<

I think I might +/- understand the basics of it.
We're talking two separate cooling mechanisms. The rough - backed mirror will
have faster cooling via convection. But the smooth - back mirror will have
faster cooling by radiation.
I have to wonder if it might not even out, done either way.
The rough - back might have to either be cleaned occasionally, or very
rough, to avoid insulating dust buildup.

Scott

[Alan]

Del,

My main point is that if people can haul around 25" Dobs, there is no reason
they can not manage an 8" APO. A 25" Dob is not going to fit in your trunk.

The same ingenuity used to make Dobs more portable can be applied to larger
refractors. A removable lens and cell that would maintain collimation would
not be difficult. The tailpiece can either come off or slide into the tube
to shorten it for transport (the latter gives you a lot of in-travel).

Clear skies, Alan

"Del Johnson" <dela...@san.rr.com> wrote in message

news:fqLx6.138431$GV2.35...@typhoon.san.rr.com...
> There are two reasons for this:
>
> 1. The refractor is generally a lot longer for the same aperture and
> generally does not dissassemble to fit in an automobile. I only need the
> trunk of a sedan to transport my 12" reflector for visual observing. No
van
> or SUV required.
>
> 2. The refractor must be lifted quite a bit higher when mounted. The
> center of gravity of a typical large Dobsonian is typically less than two
> feet off the ground.

[Alan]

Ron,

Modern 8" APOs tend to be around f/8 or f/9. While they may look
intimidating, I really don't see why they should be considered less portable
than some of the huge Dobs people are hauling around.

Clear skies, Alan

"Ron B[ee]" <ro...@home.com> wrote in message

news:pqWx6.105754$o7.41...@news1.rdc1.sdca.home.com...

[Jon Isaacs]

>My main point is that if people can haul around 25" Dobs, there is no reason
>they can not manage an 8" APO. A 25" Dob is not going to fit in your trunk.

>The same ingenuity used to make Dobs more portable can be applied to larger
>refractors.

I think the difference here is the payoff. The images from a 25 inch DOB are
certainly a great deal more impressive than an 8 inch APO and make the
difficulty of transport worthwhile.

Also, Newtonians are simple and easily fabricated from simple materials. This
is not really quite the case with APO refractors.

jon isaacs

[WHALEN44]

Hi Scott,

You have a point! I assume RC tried both with his MCT's, and found polished to
cool faster with his mechanical design.

[Richard Anderson]

A good 12" Newtonian will beat the 8" apo on all objects so
hauling around a 25" Dob isn't really a requirement.
-Rich

[WHALEN44]

Hi Rich,

Have you ever used a high quality 8" APO?
If not, how can you make this statement?

>A good 12" Newtonian will beat the 8" apo on all objects so hauling around a
25" Dob isn't really a requirement.>

[CHASLX200]

>Subject: Re: Best planetary scope? 8" APO?

>From: rande...@aol.com (Richard Anderson)
>Date: 4/5/01 3:44 PM Eastern Daylight Time
>Message-id: <3acd73b8.70989482@news>

>
>A good 12" Newtonian will beat the 8" apo on all objects so
>hauling around a 25" Dob isn't really a requirement.
>-Rich

**************************
You can bet i wont haul around a 24"Dob, hell , you can't even give me one!!!

Nothing bigger than 14.5" Starmaster for me.
And a 8" APO is not bigger in size and weight. than my 5" f16 Photo EQ
Unitron...

Chas P.

[Chris1011]

>>A good 12" Newtonian will beat the 8" apo on all objects so
hauling around a 25" Dob isn't really a requirement.>>

Another untested statement with no actual side by side confirmation.

I would say without any actual testing that a good 8" Apo will easily beat a
12" Newt when it comes to producing a sharp large format negative. So, in some
respects, the 12" Newt loses.

Roland Christen

[Alan]

Rich,

Have you viewed side by side with an 8" APO and a good 12" Newt?

Clear skies, Alan

"Richard Anderson" <rande...@aol.com> wrote in message
news:3acd73b8.70989482@news...

[Alan]

Jon,

I think the views through a 7" or 8" APO are well worth the effort.

After a while you just don't want any more Newtonians <g>. (Well, to be
honest, I think I'd really like a 25" when I retire.)

Clear skies, Alan

"Jon Isaacs" <joni...@aol.com> wrote in message
news:20010405083759...@ng-bk1.aol.com...

[Ratboy99]

>Rich,
>
>Have you viewed side by side with an 8" APO and a good 12" Newt?
>
>Clear skies, Alan

I've been doing some comparisons between my 18" stopped down to 6.5" f13,
unobstructed, and my 10" f6 reflector. The idea was to try to talk myself out
of spending the money to purchase a 6" apo refractor for observing Jupiter,
thus saving myself great expense. After having done so I have my doubts about
what Rich has said about comparing an 8" apo to a 12.5" Newt. I have *begun* to
come to the conclusion that even with the small (less than 20%) obstruction
that my 10" enjoys, it still does not make up enough contrast to beat 6"
unobstructed aperture on contrast on *Jupiter* (we are *not* talking contrast
on DSO's here). There is furthermore the issue of seeing affecting the larger
instrument more when observing Jupiter. I still have not taken into account all
of the variables, such as glare from the larger aperture causing some
irradiation, and I am waiting on a more delicate spider for the 10" with one
less vane and thinner ones at that. But I have failed to convince myself that
there is no purpose for a 6" apo, on the contrary one would fit in very well
with my collection. I would just stick with the masked 18" but it is still a
bit big, and it takes a while to cool and there are still some tube currents.
But the core images are there solid, and they are damn nice..damn nice. Double
stars, in particular, are astounding. A 6" apo is not in the budget for
everyone and my 10" Newt is certainly no slouch. Even though it loses a tad
contrast on Jupiter, I think that is the only subject that it would not beat
any 6" scope on visually regardless of circumstances (haven't tried Mars yet).
Furthermore it resolves more detail than the smalIer aperture. I would not
hesitate to make it my primary scope. Still there is plenty of room for apos
for visual use, and as an on-line contact once pointed out to me, they are
apples and oranges and really defy comparison. We are truly fortunate to have
so many choices at our disposal.

[vahe sahakian]

A comment on the subject of contrast and Jupiter.
I have A 6.1" apo and also a 10" MCT with 22% obstruction and have done extensive
comparison between these two instruments on Jupiter.
As you are well aware of, Jupiter does not take magnification well, with the apo
the maximum power that I can use is around 220x, above that the contrast begins to
wash out, at around 300x the image is reasonably sharp but most of the contrast is
gone, not a pretty sight.
With the 10" at 300x Jupiter appears crisp with nearly most of the contrast of the
apo at 220x. For 10" about 300x is the optimum on Jupiter, above that contrast
starts to wash away.
All in all the apo will give you higher contrast on Jupiter but at lower powers, if
you crank up the power the 10", despite the obstruction, will produce higher
contrast image.
These observations were done with binoviewer using Tak LE's and Zeiss orthos.

Thanks,
Vahe

[Ratboy99]

>All in all the apo will give you higher contrast on Jupiter but at lower
>powers, if
>you crank up the power the 10", despite the obstruction, will produce higher
>contrast image.
>These observations were done with binoviewer using Tak LE's and Zeiss orthos.

I'm finding that any scope I am using here in the Rockies is crapping out above
250x or so on Jupiter. I think you make a good point about the binoviewer, I
just got one and from what I understand they can help with the contrast issue.
I still have a lot to learn about this, I was just giving some preliminary
observations.

[Richard Anderson]

No, i've used a few 7"s though.
-Rich

[Richard Anderson]

Visually, I've seen a 12" Newtonian with a Ceravolo mirror beat a
7" apo, but maybe that extra inch makes all the difference?
-Rich

[Richard Anderson]

I thought it was more or less understood, but of course seeing is
critical to saying a 12" scope beats an 8." But the seeing need not
be perfect constantly; You only need a few seconds every minute to
take advantage of a the larger aperture.
However, if a 6" scope of any kind is giving you your best views of
Jupiter, then there can only be two reasons for it;
-Your seeing is bad
-Your larger scope isn't as good as it should be.
-Rich

[Markus Ludes]

A good 12" Newtonian will beat the 8" apo on all objects so
hauling around a 25" Dob isn't really a requirement.
-Rich

 

Rich,

 

I have a good Newtonian 16"F/5 with 15 % C.O., high quality multicoated optical window, 1/8.4 wavefront and 98.3 % strehl tested against an Apo 8"F/9 with 1/8 wavefront p.t.v. and 98.4% strehl last autum on Planets. Seeing was damm good, maybe 8~9/10.

 

The Newtonian is an planetary optimizest instruments and showed much brighter images , but the Apo showed the fainter images more crisp and with a bid more details.

 

I have done that comparation and know from practical side the results, how about you ? Just an theorital impression or what ?

 

Markus

[Valery Deryuzhin]

Markus wrote:

 

>Rich,

> 

>I have a good Newtonian 16"F/5 with 15 % C.O., high quality multicoated optical window,

>1/8.4 wavefront and 98.3 % strehl tested against an Apo 8"F/9 with 1/8 wavefront p.t.v.

>and 98.4% strehl last autum on Planets. Seeing was damm good, maybe 8~9/10.

>

>The Newtonian is an planetary optimizest instruments and showed much brighter images,

>but the Apo showed the fainter images more crisp and with a bid more details.

> 

>I have done that comparation and know from practical side the results, how about you ?

>Just an theorital impression or what ?

>

>Markus

 

 

Markus,

 

I know that you do speak about our 16" scope. It is simply impossible, that such

perfect scope like our 16"  will deliver under 8-9/10 seeing an images less

crisp than 8" any scope.

In 16" scope even first diffrection ring is the same size as Airy disk in 8" scope!

and Airy disk in 16" is 2x smaller than Airy disk in 8" . because a quality is the

same it is against law of physics that 8" produce sharper than 8" images.

 

With THE SAME success, I will say, that our 4" scope produce sharper image

than your 8" .

 

Only smile and smile. You always say what you NEED NOW. 

 

Note, pleasse, if  one will read your review of our 16" at the Cloudy Night, he will

be assured by YOUR OWN words, that this scope outperforms 10" APO and

at least equal to 12" apo.

 

 

Valery Deryuzhin

ARIES.