8"SCT or 6" Mak - better palnetary scope?
J. Alton
mid-priced OTA primarily for planetary observation.
I'm leaning toward a 6" russian Mak-Cass, but am also considering a
C-8 (or the 5" Intes Mak-Newt).
I'll probably be putting them on a Vixen GP.
I'm interested in hearing from people who have had experience with
these scopes. Generally, does the increased contrast of the Mak-Cass
satisfactorily compensate for 2" less aperature?
The SCT, however, may weigh about 5-6 pounds more and be less stable
on the GP.
Thanks for your input.
Brian Murphy
PV. The MN-56 was a better planetary performer. I believer this is due to
the smaller central obstruction of the MN.
Brian
"J. Alton" <jo...@nospam.com> wrote in message
news:39fb38b2...@news.capital.net...
Ron Wodaski
210. It's got incredible contrast, and weighs noticeably less than a C8.
It's a Cassegrain design (not a Schmidt-Cass), and thus has less glass. You
pay quite a premium for the extra performance, however. Also worth a look
would be the smaller Mewlon, I believe it's a 180 f/11.5 scope.
Also, look for a 7" Meade Mak OTA; these typically have quite good optics. I
don't often see them for sale used without the mount, but there may be some
out there. The only problem might be the weight, which I don't have handy to
check it out.
--
Ron Wodaski
http://www.newastro.com
"J. Alton" <jo...@nospam.com> wrote in message
news:39fb38b2...@news.capital.net...
jacop...@my-deja.com
I had a 7" meade mak and, on planets, it was not showing anything more
than the c8 I had. A little better contrast, and that was about it.
Of course, maybe Intes are much better than meade and they claim a
wavefront error better than average.
Eventually I eneded up with a c11. Aperture wins.
One nice thing of Intes is portability.
just my opinion
jl
>
Sent via Deja.com http://www.deja.com/
Before you buy.
Jim Mueller
always wins, if the optics on both scopes are on a par. The optics on my
G-8 are excellent with near perfect star tests.
Finally, the central obstruction on a 6" Mak is no smaller, percent wise,
than on an 8" SCT.
"J. Alton" wrote:
--
Regards
jim mueller
Tech Support
http://www.mp3homestudio.com
Andrea Tasselli
I have all of them, a 6" Intes MK67, a 6" Intes Micro MN66 and a C8. Of the
three the best performer on planets is definitely the MN66, followed by the
MK67 and, distanced, the C8.
I've also compared the MK67 with other C8s and LX200 (8" and 10") and while
the larger aperture of the 10" yielded more details (but not wastly more)
the image in the MK67 was definitely more pleasing and contrasty. As per the
other 8" simply no game. The best C8 of the bunch showed the same level of
details on Saturn and Jupiter to my eyes as well as to the owner's. So much
so that he bought a MK66. All the compared 8" and 10" SCT were fairly recent
scopes so some vintage (early '80) C8s got to be better.
The GP is perfectly apted to work with the C8. No stability problems, even
with the AHL-150 tripod (with it isn't this much stable on its own).
Just my 2 cents.
Clear Skies
Andrea
Chris & Kathy Jackson
on your original list, but it will fit on your GP mount. It will be shaky
yes, but the point of the matter is: the C9.25 completely, completely,
without reservation, blows away the Alter 603. Details are sharper, the
aperature brings more to bear, and more magnification is possible. Plus, as
long as you are out during the night, with the C9.25 you can also catch a
globular or two with very pleasing results. You can buy a C9.25 on a CG-5
mount for just over $1200, and I think Astronomics will even throw in a dual
axis drive for free. I've had the 9.25 on a CG-5 and performance is
acceptable. Just be careful while focusing, while getting your eye to the
eyepiece, and replace the aluminum legs. The Mak-Cass on the mount will run
you equally as much, and you'll be stuck with a much less capable telescope.
Unless airline portability is your MAIN concern, there is no better way to
spend $1200 in the telescope world than a C9.25.
Chris...................................
J. Alton <jo...@nospam.com> wrote in message
news:39fb38b2...@news.capital.net...
Ron Wodaski
well as many other things <g>). I was just concerned about the weight on a
GP.
But for just pure value, the 9.25 is hard to beat.
--
Ron Wodaski
http://www.newastro.com
"Chris & Kathy Jackson" <txja...@dialaccess.com> wrote in message
news:39fb6...@newsa.ev1.net...
Mike McIsaac
I started in this hobby with a C8 which provided unimpressive planetary
performance. Moved on to an Intes-Micro Alter 703 Deluxe Mak-Cass
which was a little better. Then I got a bad case of aperture fever and
am I glad I did! I got a C-9.25 and a Losmandy GM-8 and I'm happy as
can be. The planetary performance of the C-9.25 is almost refractor-
like which is most unusual for a compound telescope. The first time I
turned it on M42 i literally gasped. I'd NEVER seen so much detail
before.
Two caveats though: it takes a while to cool down (but so does any Mak)
and with 9.25" of aperture, the atmospheric conditions need to be
pretty steady to use the scope to its full potential. I don't even
bring mine out unless the seeing is almost perfect (which doesn't
happen often as close as I live to the stormy Gulf of Alaska).
Good luck and clear skies!
Mike McIsaac
60*N 150*W
In article <39fb6b65$1...@news.nwlink.com>,
--
*********************************************
186,000 miles per second: its not just a good
idea, its the law!
*********************************************
Bob Berta
fine....just make sure you colimate any SCT occasionally for best
performance. A well colimated SCT will be hard to beat by a 6"
aperture. The obstruction on a 8" SCT reduces its aperture down to
about 7 1/2" equivalent aperture. The Mak Newts are good scopes
although of smaller aperture...for DSO the 8" will show more detail in
side by side comparisons although the Mak Newt might be a little
sharper. I have compared a lot of Maks to SCTs and there is enough
variation from sample to sample to make it a wash unless aperture is
considered. The biggest problem with Mak Newts and Maks for me is their
slower aperture which makes them not very ideal if you want to do
photography though them. The SCT rules here....if you have the money
and are mostly interested in planetary performance the Celestron 9 1/4"
SCT is really outstanding and would be my first choice over any of the
other scopes. If you even think you might want to do some CCD imaging
down the road....I would only consider the Celestron 8" Fastar
compatible scopes...the Deluxe or U2K. They are amazing instruments for
CCD imaging. I have one and can't think of any other combination at
anywhere the price that can even begin to compare. The Maks do have one
big draw back...they take a long time to cool down and in fact
depending on how much the temperature changes in your observing
site...may never equilize. The Meade 7" Mak has decent optics but a
lead counterweight inside and that evidently causes it to take quite a
bit longer to cool down than other scopes..even other Maks.
Michael Kreuzer
> always wins, if the optics on both scopes are on a par. The optics on my
> G-8 are excellent with near perfect star tests.
>
> Finally, the central obstruction on a 6" Mak is no smaller, percent wise,
> than on an 8" SCT.
It's interesting (this is sort of OT, I know) that the 7" meade mak sells
for more than their 10" schmidt cass. You'd want a whole lot of performance
for that kind of money.
imho, Michael
John Hopkins
would I have to hunt for a 'used' if I wanted one? TIA.
Yers,
/John
Get scoped: http://www.darkhop.com/astronomy.htm
The alt.fan.frank-zappa CD: http://www.RALF.com/CD/
"Mike McIsaac" <mike_m...@my-deja.com> wrote in message
news:8tg1ff$kod$1...@nnrp1.deja.com...
Paul Gustafson
"John Hopkins" <dar...@home.com> wrote in message
news:_1TK5.12193$Y6.41...@news1.mntp1.il.home.com...
> Who makes this C-9.25? And is it something that would be out there now or
> would I have to hunt for a 'used' if I wanted one? TIA.
Celestron. See:
http://www.company7.com/celestron/products/sch11.html
Gus
DBogan3220
If it were myself I would definitely consider the Celestron 9.25 SCT.
You have the larger aperture. Which not only works for you with lunar and
planetary but for deep sky as well, Celestron seems to be producing these
scopes with exceptional optics and consistantly every time I have yet to hear
of a bad one. You do need to learn how to finely collimate your optics there is
no way around that. I would suggest acquiring a set of "Bobs Knobs "
see Web Link http://www.bobsnobs.com/
and I would invest in a Lymax SCT cooler to help exchange the air inside the
tube with the outside air this guy really works. see this link
http://www.lymax.com/lesa/catalog/sctcooler/sctcooler2.shtml
I've owned my 9.25 SCT Ultima this is the one with with the fork mount and I
also have the countermechanism for the focuser, for the last two years. It sets
up very quickly gives. Excellent views even at very high power using a 2.8mm
Tak Hi ortho I get 837x when the seeing is good I get a very good image. The
optics in my SCT are definately better than 1/4 wave and except for the cooling
question and having to collimate the scope which is no problem with the
Bobsnobs. These are the only caveats I can find. The aperture will blow
anything of six inches aperture out of the water. The optics will compete very
well against the Meade 10 inch LX200 and the C-11 SCT. I think this particular
scope and SCT is one of the best buy's out there, bar none.
Clear Skies
Dwight L Bogan
Jim Mueller
Mak, has earned a reputation bigger than life. Perhaps it's because of the
legendary Questar.
I observe from a light polluted suburb and last night we had the best skies in 3
months. The skies were very tranparent (for this location) with very little
turbulance. This is unusual for the Midwest.
Jupiter's belts were revealed in a way that I had never seen before. The banding
was numerous, distinct and seperated into finer and finer belts. I quickly went
into the house to grab Oct's issue od S&T to identify exactly what the heck I
was seeing.
I observed the SSTeB, STeB, SEB, EB, NEB,NTeB, NNTeB and NPR.This told me that
my scope was limited only by the seeing. I had to reall concentrate to identify
these features but they were there and distinctly seperated. At very brief
moments of steady seeing, the planets incredible detail froze into a CCD like
photograph that caught me gasping expletives under my breath.
I was able to use a 7mm Ortho for the first time. The 9mm and 12.5mm Orthos
showed the most pleasing images, however. Seeing is by far the most limiting
factor in observing for me.
In my opinion if you have $1300 to spend, a G-9.25 is the way to go but you will
have to upgrade the mount eventually. If you have $1000 then the G-8 is a no
brainer and the CG-5 mount is more suited to this lighter load. With home made
oak tripod legs, my CG-5 is pretty darn good.
Michael Kreuzer wrote:
--
Joseph O'Neil
<sup...@mp3homestudio.com> wrote:
>In marketing...perception is more important than reality! For some reason the
>Mak, has earned a reputation bigger than life. Perhaps it's because of the
>legendary Questar.
-snip-
Actually, I think it is because of the legendary Ceravolo
Mak-Newts. I would put my 145mm Ceravolo mak-newt against any Meade
or Celestron 8" SCT and watch the competition fall away in dust. :)
There should be a distinction made as well between mak-newts
and mak-cass scopes. From my limited experience, I find little
difference between a well made SCT and a well made mak-cass. But
Mak-newts, ah, that's a different cookie altogether. For visual use
at high powers on the planets, a well made mak-newt - and i specify
well made - will not only surpass any SCT, but snip at the heels of
most top end refractors.
joe
Alan French
Have you tried it? Some of the SCTs around these days are pretty good.
Although the 5.7" Ceravolo Newt-Maks are certainly wonderful scopes, there
is simply no magic that will turn one into an 8" scope.
Clear skies, Alan
"Joseph O'Neil" <jon...@multiboard.com> wrote in message
news:39fc386b...@news.multiboard.com...
> [SNIP]
> Actually, I think it is because of the legendary Ceravolo
> Mak-Newts. I would put my 145mm Ceravolo mak-newt against any Meade
> or Celestron 8" SCT and watch the competition fall away in dust. :)
> [SNIP]
Vahe Sahakian
I find little
> difference between a well made SCT and a well made mak-cass.
When it comes to well made MCT's your experience is indeed very limited,
or let me put it this way, if you ever look at the planets with one of
the TEC planetary MCT's you will quickly discover that they are not in
the same league as SCT's, in fact their images are very similar in
contrast and resolution to a well made apo.
There is a big difference between a well made MCT and an overpriced MCT,
Questar is the best example of an overpriced MCT, for a well made one
you should consider a TEC and or an AP.
Thanks,
Vahe
jacop...@my-deja.com
va...@flash.net wrote:
> Joseph O'Neil wrote:
> I find little
> > difference between a well made SCT and a well made mak-cass.
>
> When it comes to well made MCT's your experience is indeed very
limited,
> or let me put it this way, if you ever look at the planets with one of
> the TEC planetary MCT's you will quickly discover that they are not in
> the same league as SCT's, in fact their images are very similar in
> contrast and resolution to a well made apo.
Given the same wavefront error and CO, is MCT a better design than a
SCT for high contrast and why?
thanks
jl
Jim Mueller
obstruction for both instruments is the same, what magical attribute does
the MCT have to perform better? I'm curious.
Vahe Sahakian wrote:
--
Vahe Sahakian
> SCT for high contrast and why?
Given the same wavefront error and co, both the SCT and MCT should be
about the same.
The reality is that in the world of mass produced optics, given the same
limited production budgets, an MCT with their all spherical surfaces
have a better chance of ending up with smoother optics than the SCT's
which have an aspheric component in them. Another advantage of low lost
MCT's is the spot secondary, being a part of the larger corrector
surface it will always end up with a smoother figure than the separate
secondaries installed in SCT's.
High end MCT's are a different animal, these are produced with totally
different performance goals and can not be stacked up against commercial
SCT's (Meade & Celestron) from the performance standpoint.
My two cents.
Vahe
Mike Burley
Bob Berta wrote in part:
>
> If you are only interested in planetary performance any of them will be
> fine....just make sure you colimate any SCT occasionally for best
> performance. A well colimated SCT will be hard to beat by a 6"
> aperture. The obstruction on a 8" SCT reduces its aperture down to
> about 7 1/2" equivalent aperture. The Mak Newts are good scopes
> although of smaller aperture...
Not true. Mak-Newts can be had in sizes from 5" to 16". See:
http://www.burnettweb.com/ite/telescop.htm
<SNIP>
> The biggest problem with Mak Newts and Maks for me is their
> slower aperture which makes them not very ideal if you want to do
> photography though them.
While it's true that most Mak-Cass scopes tend to be on the slow side,
the Mak-Newts from Intes and Intes-Micro are f/6!
<SNIP>
> The Maks do have one big draw back...they take a long time to cool down and in fact
> depending on how much the temperature changes in your observing site...may never equilize.
The Russian Mak's now have filtered OTA coolers available that can cut
cooldown time by half. I suspect one of the Intes/Intes-Micro 6"
Mak-Newt's would more than hold it's own against an average Celestron or
Meade 8" SCT in planetary performance. There is no question which would
have the edge in contrast - absolutely none.
<SNIP>
Mike in Oregon
Vahe Sahakian
>
> If the SCT's optics manufactured are as well as the MCT's optics and the
> obstruction for both instruments is the same, what magical attribute does
> the MCT have to perform better? I'm curious.
I am curious as well.
As far as I know there is only one company that manufactures SCT's to
very high standards, they are in Europe and I can not remember their
name at this time.
As for magical attributes on the part of the MCT, I am afraid that this
would be a question for Roland or Yuri to address.
Thanks,
Vahe
Brian Murphy
an F-10 SCT. Many of the current Russian MCT's are corrected to 1/6-1/8 wave
PV. I've never looked through an 8" SCT that was this good, although I'm
sure some are out there.
Brian
"Jim Mueller" <sup...@mp3homestudio.com> wrote in message
news:39FB520C...@mp3homestudio.com...
Brian Murphy
"Vahe Sahakian"
>Another advantage of low lost
> MCT's is the spot secondary, being a part of the larger corrector
> surface it will always end up with a smoother figure than the separate
> secondaries installed in SCT's.
Which low-cost MCT's use spot secondaries?
Brian
Vahe Sahakian
> Which low-cost MCT's use spot secondaries?
Meade 7"
Vahe
Vahe Sahakian
>
> Many of the 6" MCT's are f-12. This gives a smaller central obstruction than
> an F-10 SCT.
They all come with +33% central obstruction.
Vahe
Joseph O'Neil
wrote:
>When it comes to well made MCT's your experience is indeed very limited,
>or let me put it this way, if you ever look at the planets with one of
>the TEC planetary MCT's you will quickly discover that they are not in
>the same league as SCT's, in fact their images are very similar in
>contrast and resolution to a well made apo.
Hye I woudl love to be proved wrong on this one! Anyone want
to lend me a top of the line MCT for a few months? :)
Seriously, the few samples I ahve seen were nice, but ddin't
knock my socks off, but liek you siad, my experience is limited.
joe
Joseph O'Neil
<Sue_and_A...@email.msn.com> wrote:
>Have you tried it? Some of the SCTs around these days are pretty good.
>Although the 5.7" Ceravolo Newt-Maks are certainly wonderful scopes, there
>is simply no magic that will turn one into an 8" scope.
Yep, have tried. For planetary observing, which is what I
bought it for, I have yet to see any commerical SCT from Meade or
Celestron to yet match the performance of my Ceravolo mak-newt in
terms of resolution, sharpness and contrast. The only thing that will
surpass it is something like an Astro-Physics or Takahashi refractor -
to those I bow down - but not by much.
:)
joe
RAnder3127
>SCT for high contrast and why?
>thanks
It's doubtful commercial SCT's will ever
have optics as smooth as a good MCT.
Even Meade's 7" Mak-Cass with it's
38% central obstruction is noticeably
superior to an 8" SCT on planets, and this
is primarily due to the smoothness of
the Mak optics.
Because of this their planetary performance will never quite match them,
inch per inch, but the larger average size of
the SCT sometimes makes up for this.
There is no way no matter how good it is
a 5.7" MN is going to be as good as
a considerably larger scope duriing excellent seeing conditions.
-Rich
Brian Murphy
Brian
"Vahe Sahakian" <va...@flash.net> wrote in message
news:39FC8672...@flash.net...
ed_an...@my-deja.com
va...@flash.net wrote:
> As for magical attributes on the part of the MCT, I am afraid that this
> would be a question for Roland or Yuri to address.
>
> Thanks,
> Vahe
O'K. If we are talking about magical attributes - the answer is simple. We do
MAKs because we are speaking the same language as D.D. Maksutov. Bernhard
Schmidt was speaking a few other languages incl. Estonian and German, so we
can do SCT, but I pretty sure Roland will do them probably better. (-:
In short without a jokes. All spherical MAK optics is easier to control
during manufacturing (you have to have of course test plates); also,
spherical surfaces mostly could be done with much higher level of smoothness.
It does not mean that the good optics for SCT could not be done, but even we
have same quality and CO for both systems, I would check spherochromatism -
in MAKs it is smaller than in SCTs.
Regards, Yuri.
Vahe Sahakian
>
> All 6" MCT's and all f-10 SCT's have 33% c. a. ?
All current M & C f/10 SCT's have +33% cc.
All popular Russian 6" MCT's have +33% co.
8" f/11 TEC has 32% co.
10" f/12 TEC has 30% co.
The upcoming 6" f/12 TEC MCT comes with 29% co.
8" f15.5 TEC MCT has 26.5% co.
10" f14.6 AP has 23% co.
8" & 10" f/20 TEC MCT's have 22% co.
Thanks,
Vahe
Brian Murphy
Brian
"Vahe Sahakian" <va...@flash.net> wrote in message
news:39FCD5A8...@flash.net...
Dan D.
ed_an...@my-deja.com wrote:
> O'K. If we are talking about magical attributes - the answer is
simple. We do
> MAKs because we are speaking the same language as D.D. Maksutov.
Bernhard
> Schmidt was speaking a few other languages incl. Estonian and German,
so we
> can do SCT, but I pretty sure Roland will do them probably better. (-:
>
> In short without a jokes. All spherical MAK optics is easier to
control
> during manufacturing (you have to have of course test plates); also,
> spherical surfaces mostly could be done with much higher level of
smoothness.
> It does not mean that the good optics for SCT could not be done, but
even we
> have same quality and CO for both systems, I would check
spherochromatism -
> in MAKs it is smaller than in SCTs.
>
> Regards, Yuri.
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Hi Yuri.
How about curvature of field and off-axis spot size. Will an SCT --
even if figured excellently -- always have more field curvature and not-
quite-as-good images off-axis? Is this a design limitation?
And I also wonder about the typical or "average" quality (accuracy and
smoothness) of the Schmidt corrector plates found on production
scopes. I don't recall ever reading *any* information in that regard.
Perhaps these are questions for others -- SCT experts.
Best wishes,
-Dan
spoone...@my-deja.com
Dan D. <dr_...@my-deja.com> wrote:
> Hi Yuri.
>
> How about curvature of field and off-axis spot size. Will an SCT --
> even if figured excellently -- always have more field curvature and
not-
> quite-as-good images off-axis? Is this a design limitation?
>
> And I also wonder about the typical or "average" quality (accuracy and
> smoothness) of the Schmidt corrector plates found on production
> scopes. I don't recall ever reading *any* information in that regard.
>
> Perhaps these are questions for others -- SCT experts.
>
> Best wishes,
> -Dan
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>
For a nearly flat field and great overall corrections, try:
http://members.home.net/rmscott/lh_scope/index.html
This scope has all spherical optics and essentially diff limited for
beyond visual color range over approx 35mm frame. Photograph quality
should result in an even larger FOV. The radii tolerances are less
demanding than a Mak and if thickness/radii problems crop up a quick
redesign adjusting specs can restore essentially the same superb
performance. Lens/mirror spacing is noncritical and the design can be
setup such that a small secondary could be used (but why compromise
such a fine photographic setup?) Now if we could entice Yuri to make
them. :) I've made a couple of optic sets but I perfer to do Newtonians
and Yuri and his crew are much more experienced in lens/compound
systems. Sorry, Yuri, but all I can provide is English language. <grin>
--Mike Spooner
Chris1011
in MAKs it is smaller than in SCTs.>>
You are too modest. I would say something like 10 times smaller.
Roland Christen
Chris1011
How about curvature of field and off-axis spot size. Will an SCT --
even if figured excellently -- always have more field curvature and not-
quite-as-good images off-axis? Is this a design limitation?
>>
Curvature of field is the result of design tradeoffs. In the case of commercial
SCTs, the tradeoff was made between short tube to fit into a portable fork
mount and higher field curvature due to the higher curvature of the secondary
mirror. Also, coma is uncorrected in commercial SCTs, whereas in high end Maks
it is fully corrected. Off-axis astigmatism is also well controlled in these
designs.
Roland Christen
Chris1011
>>
As measured, the 6" Russian Intes Mak-Cass scopes have a clear aperture of
5.83" and central obstructions of 2.1", or 36%.
Roland Christen
lude...@my-deja.com
meashure at which backfocus behind end of tube ?
from 65 mm backfocus till 130 mm backfocus on the MK 66 the clear
operating aperatue is 150 mm, behind 150 mm vigneting starts.This was
checked out in germany . If your is diffrent, than maybe something
changed, or did you meashured that by an longer backfocus ?
best wishes
Markus
>
> Roland Christen
Chris1011
from 65 mm backfocus till 130 mm backfocus on the MK 66 the clear
operating aperatue is 150 mm, behind 150 mm vigneting starts.This was
checked out in germany . If your is diffrent, than maybe something
changed, or did you meashured that by an longer backfocus ?
>>
While the front aperture is slightly larger, the actual clear opening is
smaller than the front ring diameter by .075", or 1.9mm, making it a 148.1mm
instrument. It is the rear aperture of the front corrector that is slightly too
small. The front opening is big enough.
Roland Christen
Alan French
Well, I shall have to take a closer look the next time I see an HD 145.
There was one at WSP last year - perhaps it will return.
I dare say, though, that a well done 8" Newt with modest central obstruction
would do beter than any 5.7" Mak-Newt.
Clear skies, Alan
"Joseph O'Neil" <jon...@multiboard.com> wrote in message
news:39fca0d4...@news.multiboard.com...
\
Andrea Tasselli
Bet the name is Zen, of Italy
Clear Skies
Andrea
Joseph O'Neil
<Sue_and_A...@email.msn.com> wrote:
>I dare say, though, that a well done 8" Newt with modest central obstruction
>would do beter than any 5.7" Mak-Newt.
Hi;
Oh I agree, and th elast 10" home made dobsonain I looked
through made using a Zambuto mirror was just (as Ned Flanders would
say) scrumdilylious!
In fact, I often point out to people that one of the best
sights of Jupiter I ever had was thorugh a 16 dobsonian made with very
high quality mirrors.
Problem is, finding really good optics of any size, make, etc.
joe
Andrea Tasselli
<ed_an...@my-deja.com> wrote in message 8tihog$e3m$1...@nnrp1.deja.com...
> In article <39FC7147...@flash.net>,
> va...@flash.net wrote:
>
> > As for magical attributes on the part of the MCT, I am afraid that this
> > would be a question for Roland or Yuri to address.
> >
> > Thanks,
> > Vahe
>
> O'K. If we are talking about magical attributes - the answer is simple. We
do
> MAKs because we are speaking the same language as D.D. Maksutov. Bernhard
> Schmidt was speaking a few other languages incl. Estonian and German, so
we
> can do SCT, but I pretty sure Roland will do them probably better. (-:
Well, Baker is (or was ?) american, so Roland has no language barrier :-)
>
> In short without a jokes. All spherical MAK optics is easier to control
> during manufacturing (you have to have of course test plates); also,
> spherical surfaces mostly could be done with much higher level of
smoothness.
> It does not mean that the good optics for SCT could not be done, but even
we
> have same quality and CO for both systems, I would check
spherochromatism -
> in MAKs it is smaller than in SCTs.
>
> Regards, Yuri.
>
A monocentric Baker-Schmidt will have all spherical mirror design and
theoretically no coma or astigmatism. Fiel curvature, alas, is its bane as
well as strongly aspheric corrector plate in need of achromatisation.
Clear Skies
Andrea
Andrea Tasselli
34.5% to 36% according to my experience.
Clear Skies
Andrea
Vahe Sahakian
> Bet the name is Zen, of Italy
The SCT that I had in mind, a 10" f/15 is made by Opicon.
Thanks,
Vahe
Les Lawrence
optics, let me say that the mount is not adequate to the load despite what
the Orion catalog might imply.
Les
>I'll probably be putting them on a Vixen GP.
>
ed_an...@my-deja.com
spoone...@my-deja.com wrote:
> This scope has all spherical optics and essentially diff limited for
> beyond visual color range over approx 35mm frame. Photograph quality
> should result in an even larger FOV. The radii tolerances are less
> demanding than a Mak and if thickness/radii problems crop up a quick
> redesign adjusting specs can restore essentially the same superb
> performance. Lens/mirror spacing is noncritical and the design can be
> setup such that a small secondary could be used (but why compromise
> such a fine photographic setup?) Now if we could entice Yuri to make
> them. :) I've made a couple of optic sets but I perfer to do Newtonians
> and Yuri and his crew are much more experienced in lens/compound
> systems. Sorry, Yuri, but all I can provide is English language. <grin>
> --Mike Spooner
Hi Mike, nice project on the given web page! Use the Engine Black paint (any
hobby store) instead of ink to paint secondary edge. The combination of glued
primary and push-pull screws could cause some pinching... just my 2 cents.
yuri
ed_an...@my-deja.com
chri...@aol.com (Chris1011) wrote:
> You are too modest. I would say something like 10 times smaller.
>
> Roland Christen
>
When most of SCTs made with tradeoffs between quality and cost,
talking about spherochromatism could be a modest thing.
spoone...@my-deja.com
>
> Hi Mike, nice project on the given web page! Use the Engine Black
paint (any
> hobby store) instead of ink to paint secondary edge. The combination
of glued
> primary and push-pull screws could cause some pinching... just my 2
cents.
>
> yuri
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>
Thanks Yuri,
I wasn't too excited about the design until I ray traced Rick's version
and then decided I wanted one also! I will probably actually do some
astrophotogaphy when I get my optics finished. It was a lot of work for
a mirror maker though and I don't want a steady diet of these
projects. :) The only other 'exotic' scope I may make would be a
Schupmann refractor - maybe. Thanks for the tips. --Mike
lude...@my-deja.com
> While the front aperture is slightly larger, the actual clear opening
is
> smaller than the front ring diameter by .075", or 1.9mm, making it a
148.1mm
> instrument. It is the rear aperture of the front corrector that is
slightly too
> small. The front opening is big enough.
I dont understand. I have an MK 67/MK66 optical set in stock. I just
meashured it. The mechanical aperature of the corrector lens is 156 mm,
about 1/2 mm at the edge is not coated, so the coated diameter is about
155 mm. The front lens is covered as you say big enough, the rear is
uncovered, so why the coated rear diameter with 155 mm is not big
enough ?
Thanks for teaching
lude...@my-deja.com
va...@flash.net wrote:
> Andrea Tasselli wrote:
>
> > Bet the name is Zen, of Italy
>
> The SCT that I had in mind, a 10" f/15 is made by Opicon.
and cost about $ 7000 for OTA
Markus
>
> Thanks,
> Vahe
Chris1011
uncovered, so why the coated rear diameter with 155 mm is not big
enough ?>>
You want me to send you a photograph showing the clear aperture with a caliper?
I thought you were more astute about optics, now I wonder how much you really
know. It's all geometry my friend. I know all the tricks used by companies.
Maybe you can fool yourself, but not me.
Roland Christen
lude...@my-deja.com
Roland don't get angry, on such thin lens of the 6" mak, the beam does
not tilt our 2.5 mm on the rear surface. I am still interested why in
your opnion the rear diameter of 155 mm is not enough ? Excapt you have
another meniscuslens , than I am and the people who checked out the
clear aperature on the collimator.
Please feel free to show me the geometrie which say that 155 is not
enough
thanks
bratis...@my-deja.com
> Roland don't get angry, on such thin lens of the 6" mak, the beam does
> not tilt our 2.5 mm on the rear surface. I am still interested why in
> your opnion the rear diameter of 155 mm is not enough ?
Markus,
run a ray trace on a 6" meniscus and you will see how much the edge
rays diverge before they hit the second surface. As they exit, they
will come back, and keep diverging very little afterwards, but
INSIDE the lens they go quite steep. Yes, few mm easily.
I thought you knew this too - it's time you pushed some
glass to learn more about optics :-)
BTW, this divergence (or "displacement of entrance pupil") is
a chief advantage of a menisk comared to Schmidt plate that enables
us to achieve aplanatic systems which are more compact (both Schmidt
vs classical Mak and SCT vs MCT).
Bratislav
Ratboy99
>
>run a ray trace on a 6" meniscus and you will see how much the edge
>rays diverge before they hit the second surface.
Markus told me that the 6" mak had a 6" aperture when I asked this very
question before. Now it seems that in fact the scope has a 6" mirror and a
smaller aperture. The reason that I asked originally was that I had heard that
since 6" is a common size of mirror, that they use them and adjust the front
aperture to fit. That was why I understood that the Cerevolo HD 145 was a "145"
instead of a "152". Also, using the aperture to mask a fraction of the edge of
the mirror would serve to further increase sharpness if there were any edge
aberrations in the mirror. It now appears that the aperture actually is less
than 6" as I had suspected. This means that what available light there is is
being spread out as it travels to the second surface. So in fact it is not
collecting the light of a true 6" scope, but a bit less than a 6"er as in the
HD 145.
rat
~( );>
Chris1011
instead of a "152".>>
Ceravolo used a 6" quartz blank in his Mak because this was a standard size
available from Corning at a reasonable price. With that size mirror, a Mak-Newt
will have a smaller 145mm clear aperture. You can get larger quartz blanks cut
from large sheets, but they are more expensive because there is not some waste
material left behind.
Roland Christen
Ratboy99
>from large sheets, but they are more expensive because there is not some
>waste
>material left behind.
So, I assume that the Orion product uses a 6" blank as well.
rat
~( );>
Chris1011
>>
I would be very surprised if they used quartz.
Roland Christen
Rockett Crawford
Ratboy99 wrote:
> So, I assume that the Orion product uses a 6" blank as well.
ITE states in it's specifications that the clear aperture is 152mm.
http://www.burnettweb.com/ite/mn61.htm
Rockett Crawford
----------------------------------------------------------------------------
Capella's Observatory (CCD Imaging)
http://web2.airmail.net/capella
Yankees are #1 (hey, I lost a bet!)
lude...@my-deja.com
I am impressed, I am really impressed.
Roland spread forwhatever reason an information, I ask him to show he
come to this opinion or knowledge , and instead of an answere I am
getting an reply, that he thinik my knowledge is limited.
Roland say , I need to increase my knowledge, Bratislav read only
Rolands info and not mine and agree with Roland.
Bratislav, to you I recomment to try your ray tracing before followings
Rolands mind.
Okay lets make it clear. Do your ray tracing and you check out the
claim from Roland. The result will be the used aperature is 150 mm an
dnot less. The back of the meniscuslens is large enough.
The Meniscuslens have an mechanical diameter of 156 mm
The Meniscuslens have an coated diameter of 155 mm
The Meniscuslens is using in front an entrance aperature of 150 mm
The Meniscuslens is using an inside aperature of 155 mm without
baffling
The thickness of the Meniscuslens is 11 mm
No vigneting , Roland still dept me his geometrie to show that the
INTES design is wrong
The primary mirror of the same 6" optics have an mechanical diameter of
164 mm
the primary mirror of the same system have an coated diameter of 163 mm
I know that Roland bought at Astrofest from Garry Hand such an 6" scope
and is easily able to check out this datas and to confirm them.
Now i would be really interested why Roland , knowing it better, doing
here such an claim.
Roland please answere my above question and show me your geometrie.
The INTES design is correct and not producing an vigneting. You dept me
the answere, why you say it is not so.
thanks
Markus
In article <20001031222321...@ng-cr1.aol.com>,
Chris1011
The Meniscuslens is using an inside aperature of 155 mm without
baffling The thickness of the Meniscuslens is 11 mm No vigneting , Roland still
dept me his geometrie to show that the
INTES design is wrong The primary mirror of the same 6" optics have an
coated diameter of 163 mm
>>
While you are correct that the front ring entrance aperture is 150mm, and
perhaps the rear aperture should be 155mm, there is not 150mm of polished
glass in front, nor is there 155mm of polished glass in the rear. The edge
bevel of the glass impinges on the clear aperture in the front and the rear.
This reduces the aperture a tiny amount, about 1mm all around the edge. You
don't believe me? I can send you a photo.
The original post was in response to someone who said that the CO was 33%,
wheres I measured 36%. Even if there was no bevel on the glass, and it was a
full 150mm, it would still have a CO of 35.6%, pretty close to the 36% that I
measured due to the tiny reduced full aperture. I think you're splitting hairs
here, Markus. That silly millimeter is not worth getting all hot about.
Roland Christen
JF
not exactly the same as the Intes design, it might be close enough to answer
a vignette question.
An on-axis ray striking the front of the corrector at 75mm height leaves the
back of the corrector at 76.04mm height, and hits the primary mirror at
77.1mm height. Therefore, the clear aperture at the rear of the corrector
needs to be just over 2mm larger than the clear aperture at the entrance.
Also, the primary mirror diameter needs to be just over 4mm larger than the
clear aperture at the front of the corrector. The numbers supplied by
Markus show the clear aperture at the rear of the corrector to exceed the
front of the corrector by 5mm (155mm - 150mm), and the primary mirror
diameter exceeds the clear aperture at the front of the corrector by 8mm
(163mm - 150mm). So, no vignetting occurs for on-axis images.
For off-axis light, vignetting starts at about 0.3 degrees (0.6 degree FOV).
A 0.3 degree off-axis ray striking the front of the corrector at 75mm height
leaves the back of the corrector at 76.08mm height, and hits the primary
mirror at 81.3mm height. The primary mirror diameter becomes the limiting
factor. The clear aperture at the rear of the corrector is still large
enough. The secondary mirror needs to be about 31mm diameter at this angle.
If the secondary mirror is smaller, then it will be the initial cause of
vignetting.
The design is listed below. The central thickness of the lens is 11.24mm so
that it will be about 11mm thick at the edge. The glass is BK7. The
spacings between lens and mirrors are approximate numbers.
R1 283.473
central thickness 11.24
R2 289.930
lens to mirror spacing 800
R3 1800
mirror to mirror spacing 765
back focus 128
Jim
<lude...@my-deja.com> wrote in message news:8tpbjn$ve9$1...@nnrp1.deja.com...
(some snipped)
Chris1011
I did a quick 150mm f/6 mak-newt design to check this out for myself. While
not exactly the same as the Intes design, it might be close enough to answer
a vignette question.>>
The corrector for a Mak-Cass has quite a bit more curvature generally than that
of a Mak-Newt, simply because the corrector is correcting for a mirror of F2.5
focal ratio vs F6 for a Mak-Newt. More curvature translates into more "bending"
of the light through the thickness of the glass. All this would be a moot point
anyway, the clear aperture depends on how much polished surface is left over
after the edge bevel is subtracted.
I will grant Markus that if the bevel is kept small, this design will have
150mm clear aperture. The Central Obstruction is nevertheless still 35.6%, and
that was the original issue.
Roland Christen
Roland Christen.
Ratboy99
>
>I am impressed, I am really impressed.
>Roland spread forwhatever reason an information, I ask him to show he
>come to this opinion or knowledge , and instead of an answere I am
Hi Markus,
I assumed that Roland measured the clear aperture using a ruler. Please forgive
me if I have jumped to an erroneous conclusion.
rat
~( );>
JF
"Chris1011" <chri...@aol.com> wrote in message
news:20001101161229...@ng-fi1.aol.com...
> The corrector for a Mak-Cass has quite a bit more curvature generally than
that
> of a Mak-Newt, simply because the corrector is correcting for a mirror of
F2.5
> focal ratio vs F6 for a Mak-Newt. More curvature translates into more
"bending"
> of the light through the thickness of the glass. All this would be a moot
point
> anyway, the clear aperture depends on how much polished surface is left
over
> after the edge bevel is subtracted.
>
Oops! Thanks for the correction. I agree, it's a moot point.
I also mistakenly added thickness to the center of the corrector to make the
edge thickness equal to 11mm. Should have subtracted since the lens is
thinner in the middle. Hmm, gotta find someone to check my work since I'm
apparently not checking it.
Jim
bratis...@my-deja.com
lude...@my-deja.com wrote:
> Hi Rat, hi Bratislav,
>
> I am impressed, I am really impressed.
> Roland spread forwhatever reason an information, I ask him to show he
> come to this opinion or knowledge , and instead of an answere I am
> getting an reply, that he thinik my knowledge is limited.
> Roland say , I need to increase my knowledge, Bratislav read only
> Rolands info and not mine and agree with Roland.
> Bratislav, to you I recomment to try your ray tracing before
followings
> Rolands mind.
>
> Okay lets make it clear.
Yup, let's make it clear.
6" is 152.4 mm. A typical mak cassegrain corrector will have R1 of
some 150mm or so. With thickness of 11mm, that requires diameter of
second surface of 156.2mm for no vignetting. With back set at 155mm,
clear aperture is around 148mm, just like Roland said. Regardless of
front ring size.
Yes, it is few mm only. But we are talking facts, no ?
BTW, your web page states clear apertures for MK66&67 as '152mm'.
Bratislav
PS not that anyone will see the difference between 0.33 and 0.36
obstruction or difference between 148 and 152mm aperture.
bratis...@my-deja.com
> With back set at 155mm,
> clear aperture is around 148mm,
OUCH ! Mea culpa. Should be 'around 150mm'. Too hasty at the
keyboard entering the data into raytrace.
Apologies <:-(
Bratislav
ed_an...@my-deja.com
Rockett Crawford <Roc...@Audiotel.com> wrote:
> Ratboy99 wrote:
>
> > So, I assume that the Orion product uses a 6" blank as well.
>
> ITE states in it's specifications that the clear aperture is 152mm.
> http://www.burnettweb.com/ite/mn61.htm
>
> Rockett Crawford
Lets say: it is variable and mostly depend on caliper brand. If you are
touching the cell slightly with Mitutoyo one - the aperture will be 150mm, if
you are pushing Chinese caliper with your thumb - you can get 152! It is so
simple guys....
yuri
ed_an...@my-deja.com
chri...@aol.com (Chris1011) wrote:
> I will grant Markus that if the bevel is kept small, this design will have
> 150mm clear aperture. The Central Obstruction is nevertheless still 35.6%, and
> that was the original issue.
>
> Roland Christen
> Roland Christen.
>
And 35.6% is quite god comparing to the older models: Alter603 (42%) or
MK65(7) - about 40% according to Markus's test reports.
Yuri
Yuri
Bill Becker
You and Roland must be using your binoviewers too much!
Thanks for the info on the MK 65's c.o....I guess that's why the image
is not as bright as what I hear about newer models. It does make the
detail of Jupiter easier for me to discern though.
Bill
Bill
lude...@my-deja.com
> While you are correct that the front ring entrance aperture is 150mm,
and
> perhaps the rear aperture should be 155mm, there is not 150mm of
polished
> glass in front, nor is there 155mm of polished glass in the rear.
Roland,
I dont know what you hold in your hands, but the INTES MK 67 and MK66
we have in our hands have an polisched and coated 152 mm front
aperature and an polished and coated 155 mm rear surface.
The edge
> bevel of the glass impinges on the clear aperture in the front and
the rear.
right in front it decrease the optical aperature to 152 mm and in rear
it limits to 155 mm aperature.
> This reduces the aperture a tiny amount, about 1mm all around the
edge. You
> don't believe me? I can send you a photo.
The glas is 156 mm aperature , so the 1 mm bavel is agreed.
>
> The original post was in response to someone who said that the CO was
33%,
> wheres I measured 36%. Even if there was no bevel on the glass, and
it was a
> full 150mm, it would still have a CO of 35.6%, pretty close to the
36% that I
> measured due to the tiny reduced full aperture. I think you're
splitting hairs
> here, Markus. That silly millimeter is not worth getting all hot
about.
I agree, but your point to which I answered ,was the geometrie of the
corrector lens is wrong and not 150 mm aperature using. About nothing
else I am discussing with you.
lets stop this discussion because of 1 mm
best wishes
Markus
>
> Roland Christen
lude...@my-deja.com
>
> I will grant Markus that if the bevel is kept small, this design will
have
> 150mm clear aperture. The Central Obstruction is nevertheless still
35.6%, and
> that was the original issue.
due this discussion, I found something wrong posted on my web, which
will be changed now. I just meashured the baffle diameter of the
secondary , which is 53 mm, by an 150 mm clear aperature this reflects
in an 35,33 % central obstruction. The INTES primary mirror is conical
and does not produce additional vigneting.
thanks
Markus
>
> Roland Christen
>
> Roland Christen.
lude...@my-deja.com
1, my webside states by the technical specifications 150 mm , not 152 mm
this I meashured long time ago. I did not meashured the new modells
where INTES say aperature is now 152 mm , but will do it on the next
shipment. I only meashured now the clear aperature of an MN 61 which
have 152 mm, so I expect the MK 67/MK 66 could have now also 152 mm. I
am sorry, that I not update any part of my webside from time to time,
but I will take more care on that mm in future.
2, I talked yesterday evening with the optical designer from INTES by
phone. He states the clear aperature is 152 mm and the back corrector
needs for using that 152 mm aperature 155 mm. I am not an optical
designer , so i will try to get some design informations. However I
also called Valery last evening and he told me in that design the 155
mm back aperature should be enough to produce no vigneting.
3, if you have no optical design, you can do only speculations and
running an similar design, right ?
4, Whatever datas will be correct, after getting the next shipment in a
few weeks I will do the correct updates about clear aperature and
central obstruction.
5, For past scopes I have at least an optical institut meashurement of
an MK 66 that the clear aperature is 150 mm if the backfocus is keeped
no longer than 140 mm from end of tube. This was made about an MK 66
from early 1999 and I have no reason to doubt that meashurements.
thanks
Markus
Chris1011
The glas is 156 mm aperature , so the 1 mm bavel is agreed.
>>>
The bevel on my corrector is much more than 1mm on the glass. I have not taken
the glass out to measure it. What I said is that it is 1mm all the way around
smaller than the 150mm front ring. This means about 2mm smaller in diameter.
You can clearly see the large bevel intrudes into the clear aperture both on
front and rear. The rear is slightly more bevel, so that is where the aperture
is being reduced. It may be I have a slightly larger bevel than is common for
that scope.
Roland Christen
lude...@my-deja.com
The rear is slightly more bevel, so that is where the aperture
> is being reduced. It may be I have a slightly larger bevel than is
common for
> that scope.
>
> Roland Christen
>
if that is the case in your scope, than you should do an claim to your
dealer where you purchased it, since it is not normal from my experience
Markus
Chris1011
dealer where you purchased it, since it is not normal from my experience
>>
I'm not worried about a few millimeters. The optics on this little scope are
quite nice.
Roland Christen