Big Dobson

eric wrote in message ...

I already go to some star party, but here (Quebec, Canada), the biggest
apperture I see, is 18" and 20", I hear someone have buy a 28", but never
seen yet. I look trough some CGE-14", LX200 12", LX90 14"?, but, LX200 16"
interest me only for mount precision and option (can connect CCD for
guiding, connect computer for point and shoot/goto), also for the space
size
and the no need of ladder.

The RC scope interest me for the same reason, except a high advantage of
better quality, but at twice buck than any LX200-CGE.

And for the 2 dob, (25" F/5 obsession, and 28" F/4.1 Starmaster), I know
the
Obsession optic is good (OMI-Torus or Galaxy), But Don't know the quality
of
the starmaster optic (Starmaster use Zambuto for 24" or less, it's a good
one, but 28" is not a zambuto). The ServoCat/ArgoNavis Obsession drive
system seem to be really good, but I know nothing on the Sky Tracker/Sky
Commander Starmaster drive system... What I need in drive system, is a
High
performance tracking for very long picture with computer
control/planetarium
control. So, have to choose between nice tracking system with less
aperture, or bigger apperture but unknow quality tracking system.
Obsession
with all option and shipping will be near 17k$ and Starmaster with all
option but no shipping (only pick up is available for 28") is near 20k$...
So, lot off things to think... Now, I know the Dave Bonandrini option...
So,
it's another part of puzzle.

I remove the Ntt from the list for to some reason (obscursion and
collimation difficulty)

I Know the advantage and disadvantage of lot scope, but, the quality of one
is not necessery the quality of other... I try to found the best Overall
quality for less (the cheaper is the scope, the more eyepiece, stuff,
option
and CCD I can buy...), and that's why i'm so confuse... That's will cost
more than luxuous car, and near half price of new house, so that why I want
to be sure of my choice... It's one of my dreams which starts has to be
reality. And that's why I ask for comment!

Thanks for your answer and Comment!
Clear Skies!
Eric




You may try to email or call Andre , his email is he
http://pages.infinit.net/asmprod/profile.html
He is in the same general geographic area with you.
Although he lists only smaller mirrors and blanks, he can make and
occasionally makes his BVC stuff up to 32" . His prices are right, and he
can steer you in the right direction for an optician to make your mirror at
whatever price/performance point you want. From my personal experience he
answers all emails promptly and gives all the details you may need.

best regards,
matt tudor

Hi Matt,

Thanks for the tip!

Clear Skies
Eric


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(Mitch Alsup) wrote in message . com...
"eric" wrote in message ...
Hi,

I would like to know if someone know a telescope maker for 30" or bigger
Dobson (with tracking, navigation system and/or computer control and/or CCD
tracking system). Obsession dont make the 30" anymore, and Starmaster limit
is 28"... cost must be under 35000$US

After a quick survey on the web. If you want a 30"+ scope, you are
probably
going to have to grind and polish it yourself. The only people making
30"+
optics are selling the primary for more than you budget for the whole
scope.

John Hudec tells a story about the 36" optics he made for Obsession.
He tells
about how these objectives just about killed him (in a literal sense),
they
are big, unwieldly, extremely heavy, and easy to damage. In addition,
where
are you going to send it when it needs a new coating?


Thanx for info!
Eric

You should also be aware, that for the most part, a 30"+ scope is for
those
objects you can't reach in a 16-20" scope. You just can't get a short
enough
focal length to get many of the larger sky objects in the lowest power
EP,
nor does the atmosphere put up with the lowest power a 30 throws very
often.
With a 30" F/5 you have a 150" focal length causing a 31mm Nagler to
have
123X minimum power, thereby constraining you observations from 123X to
600X.

You should visit a star party where a 30"+ scope resides (or New
Mexico Skies
and rent the 30"er) to see just how big these suckers are. Hint:
although
the scope can fit in an Excursion sized SUV, the poles will not, thus
man-
dating a trailer of some 16 feet. Nor will the ladder fit in any
reasonable
sized vehicle (to reach the eyepiece/focuser.)

If you haven't do so already, I suggest you start with "The Dobsonian
Telescope" by Berry and Kriege. Reassess you desires and cost
structure,
and then seriously think about building it yourself.

I happen to have a 20"er that I built myself, I wanted to build a
25"er.
I am glad (now 5 years later) that the 20" optic fell into my hands
before
I could find a 25" optic.

Mitch

I have had the good fortune to be able to occasionally view through a
30" Starmaster owned by a consortium here in Northern California. It's
an f/4.5, With a 31mm Nagler, the true field of view is 42 arc-minutes
- not a really wide field, but wide enough for all but the largest
telescope objects. It's true that you need near-perfect conditions to
get the maximum out of this telescope, but even average conditions
provide spectacular views, expecially when it comes to galaxy
clusters, for example.

While it is quite difficult, I have seen one person put it together
and take it down. But it normally requires two people to do part of
these tasks. This particular telescope rides in a small trailer; the
ladder can ride on the roof of the vehicle that pulls the trailer
(depending on who has it at any time).

As for me, I have a 22" that I am happy with and which fits in my
Mazda 323 hatchback, with all the accoutrements.

Clear skies,
Shneor Sherman