Who makes the best Dobs?
Dave
Seems a simple enough question. Say, a 12" scope,
disregard the eyepiece to avoid confusion. Factor in
consistent manufacturing and of course optical quality.
Factor in a smooth mount with good balance. Any
preferences?
Dave
Starlord
a much better idea.
--
The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
Sidewalk Astronomy
www.sidewalkastronomy.info
The Church of Eternity
http://home.inreach.com/starlord/church/Eternity.html
"Dave" <Da...@pleasereplytonewsgroup.ca> wrote in message
news:BGFWg.118389$5R2.27122@pd7urf3no...
Joe S.
The best scope (car, rifle, shoes, cat, handsaw, furniture, windows, etc.)
is the one I bought.
pemul...@yahoo.com
required numerous modifications to the structure). Both had good optics
but optical quality can vary greatly in mass produced dobs. Having
acquired the finances,I started researching premium truss dobs. My
first consideration was quality optics. I narrowed it down to Pegasus
or Zambuto. I know many other optical companies make quality optics and
provide certification but these two imo had the best reputation. I also
wanted a removable mirror cell esp. since I wanted the ServoCat/Argo
Navis electronics and did not want to have to wash/clean mirror while
still in scope. I do almost all my observing from rural home skies but
being able to transport primary separately was another consideration. I
finally decided on a NightSky/Pegasus/ServoCat/AN and couldn't be more
pleased.
Starlord: Your Telescope Buyers FAQ is excellent but I think the SA
2000 desk version(black stars on white background) is much easier to
see and starhop from under dim red light but I prefer the Deluxe
edition.
I have been recommending S&T's new "Pocket Sky Atlas" as a first
starchart for beginners.This one *finally* has the constellation shapes
drawn in.
http://www.amazon.com/Sky-Telescopes-Pocket-Atlas/dp/1931559317
http://www.astromart.com/articles/article.asp?article_id=412
Clear skies,
Paul
Mij Adyaw
outstanding. Less than 35 pounds and Zambuto optics.
"Dave" <Da...@pleasereplytonewsgroup.ca> wrote in message
news:BGFWg.118389$5R2.27122@pd7urf3no...
Mitch...@aol.com
Dave wrote:
> Who makes the best Dobson telescopes?
You do!
See:: "The Dobsonian Telescope" Berry and Kriege
And even if you buy a DOB, you will need this book to make it work
perfectly.
Shawn
Shawn
Just an FYI to the OP, Dave Kriege went on to found Obsession. ;-)
Shawn
Starlord
the atlas part.
--
The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
Sidewalk Astronomy
www.sidewalkastronomy.info
The Church of Eternity
http://home.inreach.com/starlord/church/Eternity.html
<pemul...@yahoo.com> wrote in message
news:1160487657.0...@k70g2000cwa.googlegroups.com...
Starlord
Hawaii and then over here the 4.25 Stargazer Steve and then my Babylon 8 and
now Babylon 10 scopes.
--
The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
Sidewalk Astronomy
www.sidewalkastronomy.info
The Church of Eternity
http://home.inreach.com/starlord/church/Eternity.html
<Mitch...@aol.com> wrote in message
news:1160491652.4...@h48g2000cwc.googlegroups.com...
pemul...@yahoo.com
Kriege/Richard Berry and consider it the most important book for ATMs
and dob owners ever written. I also have the highest respect for Dave
Kriege and what he's done for amateur astronomy. I really wanted an
Obsession but couldn't compromise not having a removable mirror cell
esp. with the advent of expensive electronics,such as ServoCat, being
mounted in the rocker box. It's essential to prevent these components
from getting wet(when washing/cleaning primary).I feel Dave should
offer a revovable mirror cell as an option on his scopes for this
reason.
Steady skies,
Paul
Uncle Bob
I don't know if it's been revised since I bought mine from Willman-Bell
three years ago, but it appears (from visiting various star parties) that
we are in another period of "Dobsonian Evolution".
The "new" dobs contain no plywood. They are primarily of aluminum
construction, with very minimal, low "ground boards". This has evolved to
basically, an aluminum ring placed on the ground--sometimes flat,sometimes
tubular, on which the structure rotates.
The "rocker box" which used to contain the mirror box, has disappeared. In
its place are two aluminum plates, cut with high pressure water jets, with
an arc-shaped bottom edge, which rests on roller bearings attached to a
carriage that rotates on the new "ground ring". The aluminum plates are
cross connected by the mirror cell frame. All this keeps the height of the
telescope as low as possible.
The secondary cage is now a secondary ring--just a single plate aluminum
ring containing the spider, focuser, light baffles and truss attachment
points, of which there are six instead of eight these days.
An example of the "New" Dobsonian can be found here:
http://www.siderealtechnology.com/28inch/RTMCBoth.jpg
The above example uses cables under tension to provide stiffness to the
structure. Also note the rather elaborate drive system--this particular
telescope is a go-to using bluetooth wireless to connect it to the owner's
laptop. The scope serves as a development platform for the owner's
servo-controller systems. It has an aperture of 28". (Although the image
quality is good, it isn't spectacular.)
One final example of the "new" dob is from the page of the fellow I
attribute much of the evolution process to, Bruce Sayer, of the SVAA in
California.
His beautiful 20" can be found here:
http://www.foothill.net/~sayre/20-in.%20telescope.htm
Just my thoughts on the "best dobs".
Clear Skies,
Uncle Bob
Fairfax, CA
Chris L Peterson
>I don't know if it's been revised since I bought mine from Willman-Bell
>three years ago, but it appears (from visiting various star parties) that
>we are in another period of "Dobsonian Evolution". ..
One could argue that these new mounts are far from "Dobsonian". Altaz
mounts have been around much longer than John Dobson. To me, a
"Dobsonian" is a _simple_ Newtonian telescope mounted on a _simple_
rocker box altaz mount, all of which can be made with _simple_ hand
tools and inexpensive materials.
IMO, calling a fancy, machined altaz mount carrying a fancy, truss tube
Newt a "Dobsonian" goes against all John Dobson represents- all the more
if it's motorized!
Not that I am against such designs in any way- I think they are great. I
just wouldn't call them Dobs.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
Greg Crinklaw
pemul...@yahoo.com wrote:
> I have and highly recommend "The Dobsonian Telescope" by Dave
> Kriege/Richard Berry and consider it the most important book for ATMs
> and dob owners ever written. I also have the highest respect for Dave
> Kriege and what he's done for amateur astronomy. I really wanted an
> Obsession but couldn't compromise not having a removable mirror cell
> esp. with the advent of expensive electronics,such as ServoCat, being
> mounted in the rocker box. It's essential to prevent these components
> from getting wet(when washing/cleaning primary).I feel Dave should
> offer a revovable mirror cell as an option on his scopes for this
> reason.
If you were to have the skills necessary to build your own scope using
his book, I'd think it a relatively simple matter to modify the design
such that the mirror cell was easily removable. I say easily, because
it is, of course, removable simply by unscrewing the bolts.
But more to the point, why not remove the mirror from the cell to wash
it? After all, mirrors should not be washed more than once every few
years. It isn't that difficult to remove the mirror for washing. I've
done it twice now with my 18. If this is your only reason not to go
with the Obsession design, in my opinion it's not a very compelling one.
Greg
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye
Chris L Peterson
<theskyhou...@yahoo.com> wrote:
>But more to the point, why not remove the mirror from the cell to wash
>it? After all, mirrors should not be washed more than once every few
>years. It isn't that difficult to remove the mirror for washing. I've
>done it twice now with my 18. If this is your only reason not to go
>with the Obsession design, in my opinion it's not a very compelling one.
IMO how often you wash your mirror depends on your conditions. It also
depends on how critically you observe. Even a little dust causes visible
degradation (for instance, the difference between ordinary and highly
reflective coatings). Most professional telescopes have their mirrors
cleaned about twice a year.
There are compelling reasons to keep your mirror clean (balanced of
course by the potential of damaging it when cleaning- not likely if you
are careful).
pemul...@yahoo.com
I don't have the skills to build my own and yes there were some other
reasons. There is no way I could go a few years without washing my
mirror.I do it twice a year because of the dust that builds up on
primary surface. I keep it fully assembled in garage and take every
precaution to keep dew from forming,etc and still have enough dust to
require cleaning at least twice a year. I have 20" and it's the largest
mirror I feel I can safely lift by myself. It makes it so easy to
remove mirror cell and put on dolly to take to house without having to
tear down scope and lift out of mirror box which creates more stress on
back.
At the time NightSky was significantly cheaper than Obsession with same
options but I just checked and see that they are essentially identical
now(within $1). NightSky did have the electrical package that I wanted
that Obsession didn't offer at the time.And the fact that Nightsky was
within easy driving distance also factored in since I wanted to pick up
scope.
Paul
BTW I love your Sky Tools 2 software. The charts are great and the log
feature is superb as are the observing lists etc etc etc.
Joe S.
"Uncle Bob" <he...@home.org> wrote in message
news:pan.2006.10.10....@home.org...
More proof that a simple, foolproof design that anyone can duplicate in a
basement workshop with simple tools can be turned into a device that
requires a degree in mechanical engineering and a workshop full of computer
controlled milling equipment.
And after that rant, I'm back to my cave to contemplate the demise of the VW
Beetle and the air-cooled 4-banger.
Greg Crinklaw
> On Tue, 10 Oct 2006 12:11:24 -0600, Greg Crinklaw
> <theskyhou...@yahoo.com> wrote:
>
>> But more to the point, why not remove the mirror from the cell to wash
>> it? After all, mirrors should not be washed more than once every few
>> years. It isn't that difficult to remove the mirror for washing. I've
>> done it twice now with my 18. If this is your only reason not to go
>> with the Obsession design, in my opinion it's not a very compelling one.
>
> IMO how often you wash your mirror depends on your conditions. It also
> depends on how critically you observe. Even a little dust causes visible
> degradation (for instance, the difference between ordinary and highly
> reflective coatings). Most professional telescopes have their mirrors
> cleaned about twice a year.
You must know different professional astronomers than I do. None of the
professional scopes I have ever used have been cleaned any where near
that often!
> There are compelling reasons to keep your mirror clean (balanced of
> course by the potential of damaging it when cleaning- not likely if you
> are careful).
Most people I know believe that washing their mirror is harmful for the
coating to some extent, no matter how carefully it is done. For that
reason it is accepted wisdom that mirrors should only be cleaned when
they are truly dirty, unless you are prepared to recoat them very often.
This is in fact the advice offered by the editors of Sky & Telescope, as
well as the mirror makers that I deal with, so I don't think I am out of
line in saying this. And in my own experience a little dust doesn't
make that much difference. It's a simple matter to compare views before
and after cleaning. There are a host of other things that have a
greater affect on contrast and most telescopes do a poor job with at
least one of them. Some dust on the mirror is not a major effect.
No, I'd say just the opposite. There are compelling reasons to leave it
be. Too many people are neatness fanatics when it comes to their
optics, shining a flashlight down the tube and freaking out over a few
specks of dust. The advice of most seasoned astronomers, both amateur
and professional, is that you are better off to leave it be until it is
truly dirty, and a properly stored mirror should never need to be
cleaned more than once every few years.
Greg Crinklaw
pemul...@yahoo.com wrote:
> Hi Greg,
>
> I don't have the skills to build my own and yes there were some other
> reasons. There is no way I could go a few years without washing my
> mirror.I do it twice a year because of the dust that builds up on
> primary surface.
Suffice it to say that I think washing a mirror that often is a mistake.
How often do you have it recoated? It is my understanding that even
careful washing of a mirror harms the coating and should be done very
sparingly. A little dust looks bad in the dark with a flashlight shined
on it, but in truth makes little real difference. Hey, maybe I'm wrong,
but my advice is to at least contact your mirror maker or the company
that does the coatings and see what they have to say about it.
> BTW I love your Sky Tools 2 software. The charts are great and the log
> feature is superb as are the observing lists etc etc etc.
Thanks for the kind words!
Clear skies,
John Banister
motorized setting circles? Thanks.
-John
"Uncle Bob" <he...@home.org> wrote in message
news:pan.2006.10.10....@home.org...
Howard Lester
>> Most professional telescopes have their mirrors
>> cleaned about twice a year.
> You must know different professional astronomers than I do. None of the
> professional scopes I have ever used have been cleaned any where near that
> often!
The MMT 6.5-m mirror is washed several times each year.
Howard Lester
MMT Observatory
pemul...@yahoo.com
Yes, they "go to" and automatically track. The ServoCat/Argo Navis is a
real joy to use. Very intuitive... just dial in NGC, Messier etc and
press GO TO on hand pad.You can also enter co-ordinates. Disengage
clutches if you want to star hop and re-engage clutches to track.
Stellcat now has an "easy track" feature that allows tracking without
the use of DSC's and this is just a sample of what it can do.
Clear Skies,
Paul
lynt
snip>
> The MMT 6.5-m mirror is washed several times each year.
>
> Howard Lester
> MMT Observatory
pemul...@yahoo.com
position and then hand track to new co-ordinate position.
Paul
Llanzlan Klazmon the 15th
news:1160513468.2...@m73g2000cwd.googlegroups.com:
> Actually you have to scroll to RA-DEC mode on AN which lists current
> position and then hand track to new co-ordinate position.
>
> Paul
Not when combined with the servocat.
Klazmon.
Shawn
> John,
>
> Yes, they "go to" and automatically track. The ServoCat/Argo Navis is a
> real joy to use. Very intuitive... just dial in NGC, Messier etc and
> press GO TO on hand pad.You can also enter co-ordinates. Disengage
> clutches if you want to star hop and re-engage clutches to track.
> Stellcat now has an "easy track" feature that allows tracking without
> the use of DSC's and this is just a sample of what it can do.
>
> http://www.stellarcat.com/
>
> Clear Skies,
> Paul
$3700 for my 15". It's only money.
Shawn (Bought the laminated star atlas instead :-) )
alli...@ignmail.com
Uncle Bob wrote:
> An example of the "New" Dobsonian can be found here:
> http://www.siderealtechnology.com/28inch/RTMCBoth.jpg
In that photograph, what's all that weird stuff on the outside of the
upper ring to which the truss tubes are attached? Is the secondary
mirror in there somewhere?!?
Michael McCulloch
> An example of the "New" Dobsonian can be found here:
>http://www.siderealtechnology.com/28inch/RTMCBoth.jpg
These scope designs are compact and lightweight for sure, but I cannot
see omitting a good light shroud around the light path. In my
experience, a good shroud and baffling around the focuser area makes
the difference between seeing that elusive detail and not.
---
Michael McCulloch
Dave
I appreciate it is not really a fair question, just like those questions,
Who makes the best car? Nevertheless it has given me more
than I got from FAQ reviews elsewhere. I admire those
people with the time and energy and ingenuity to make
their own. It's just not something I am able to do at this
time of my life, maybe later.
Dave
Mary Poppins
Mij Adyaw wrote:
> Teleport. They make a 10inch and a 14 inch. I own the 10 inch and it is
> outstanding. Less than 35 pounds and Zambuto optics.
>
I thought Zambuto wasnt making optics now ?
Jan Owen
"Mary Poppins" <gan...@hgnet.org> wrote in message
news:452C8087...@hgnet.org...
>
>
> Mij Adyaw wrote:
>
>> Teleport. They make a 10inch and a 14 inch. I own the 10 inch and it is
>> outstanding. Less than 35 pounds and Zambuto optics.
>>
>
> I thought Zambuto wasnt making optics now ?
>
He hadn't been making mirrors for the ATM market and general public, but for
several years was the mirror maker of choice for several of the *premium*
Dobsonian manufacturers...
But now, it would seem that the premium Dob market is not as backlogged as
it once was, so Carl Z has recently announced that he will, once again, be
making mirrors for sale to the general public...
Let the rush begin...
--
Jan Owen
To reach me directly, remove the Z, if one appears in my e-mail address...
Latitude: 33.6
Longitude: -112.3
http://community.webshots.com/user/janowen21
Howard Lester
I made a mistake. The original MMT mirrors were often washed, and we used
distilled water. But the 6.5-m mirror is washed only about every two years,
as washing risks removing the thin aluminum coating. (These big mirrors are
not overcoated as are amateur mirrors!) When we do wash it, it is with
Liqui-Nox, made by Alconox. The soap is biodegradable and phosphate free.
The mirror does get dusty, and we use carbon dioxide, on a monthly basis, to
clean that off.
Howard
Fidora Temple
Take care -
George Normandin
...
> ....... I really wanted an
> Obsession but couldn't compromise not having a removable mirror cell
> esp. with the advent of expensive electronics,such as ServoCat, being
> mounted in the rocker box. It's essential to prevent these components
> from getting wet(when washing/cleaning primary).I feel Dave should
> offer a revovable mirror cell as an option on his scopes for this
Paul,
I own an Obsession 20. There may be good reasons to have a removable
mirror cell, but washing is not one of them. Most Obsession/ServoCat owners
just cover the electronics with towels and plastic sheeting to let the water
drain out and clean the mirror in the box. I personally remove the mirror
box from the rocker box and prop it up at an angle with a few bricks under
one side. It only takes a few minutes to disconnect the ServoCat drive. I
usually clean the primary about once every 12 to 15 months.
As for the original question: I believe all of the current crop of
premium truss tube Dobs are very fine telescopes. What's "best" partly
depends on what your circumstances are and what features you want. In my
case the best "feature" was that I bought my Obsession 20 used off of
AstroMart for a great price and the seller delivered it to my house the day
after I answered his add. The scope already had some very nice mods and
refinements and it fit thru my sliding glass door. Those "features" made it
the "best" for me!
George N
Uncle Bob
That was pretty gentle for a rant, especially around here.
The guy who built that scope DOES have a degree in mechanical engineering,
but that's beside the point. (I think his drive system is overdone, btw.)
I think anyone could do a scaled-down (say 20" aperture) this with a
router and a Milwaukee variable speed drill. Maybe a saws-all. The
hardest part is still going to be the mirror.
Did you know you can cut aluminum plate with a router? Yes you can. The
most difficult thing is getting up the self-confidence to allow that
20,000 rpm cutter to kiss a metal object deliberately. ;-)
I think one could substitute some of the advanced plywood products for
some parts of the structure as well. What's that Finnish stuff they just
came out with called? Lots of very thin plies, top ply is available in
your choice of colors? Sexy stuff.
I think I'm going to convert my "Obsession Clone" to one of these types.
Maybe even make a wedge for the ring to turn it into an equatorial scope.
Then, it CERTAINLY wouldn't be a dob anymore. What could I call it?
I know--a BOB-sonian. LOL
And those VW bugs--they were really messy hydrocarbon emitters. I loved
'em (drove a '72 Split Window Westphalia for years) , but they were messy.
Regards,
Uncle Bob
Fairfax, CA
Uncle Bob
> The mirror does get dusty, and we use carbon dioxide, on a monthly basis, to
> clean that off.
>
> Howard
Hey, we're trying to curb CO2 emissions here... Do ya mind?
Use nitrogen. It's dryer, safer, and doesn't contribute to
global you-know-what. Maybe you could snag a little from that cryo tank
over there... ;-)
Uncle Bob
Fairfax, CA
Shawn
I suspect CO2 is better though, much denser than N2. Argon might be a
good compromise.
;-)
Shawn
Shawn
snip
> Did you know you can cut aluminum plate with a router? Yes you can. The
> most difficult thing is getting up the self-confidence to allow that
> 20,000 rpm cutter to kiss a metal object deliberately. ;-)
Doesn't heat become a problem?
> I think one could substitute some of the advanced plywood products for
> some parts of the structure as well. What's that Finnish stuff they just
> came out with called? Lots of very thin plies, top ply is available in
> your choice of colors? Sexy stuff.
Oooh! Got a link? I have a home project that could use that.
Thanks,
Shawn
Howard Lester
"Uncle Bob" wrote
We use it at a high altitude, so you won't notice it. ;-)
A. Pismo Clam
>> What's that Finnish stuff they just
>> came out with called? Lots of very thin plies, top ply is available in
>> your choice of colors? Sexy stuff.
>
don't know if it as rigid as the Finland birch, though.
Alain