Quote:
Originally Posted by jase
Huh? Small pockets? $13k for 12.5" Corrected DK. Perhaps cheaper than an 12.5" RC, but does it have the proven track record? PlaneWave are part owned by Celestron if I'm not mistaken.
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I did say "Astrographers", and $13,000 is much better than $25,000 dont you agree ?. Plus if people are buying cameras only for $10,000, i dont suppose you have and use Kodak Bownie for your work ??
By the way, Planewave is not Part owned by Celestron.
Two engineers left the company to form their own company taking their design with them.
I think you are refereing to the Celestron C20 years ago when they were with Celestron. Planewave is privately owned.
The CDK's have always proven themselves always, but availability was only in the 20" model only, and throwing them into the expensive end.
But 2 new models and more manufacturers are producing smaller versions. Ceravolo has the 300 model
http://www.ceravolo.com/astrograph/astrograph.php .
Recently i found out the SLOOH abservatory announced its installing the half meter CDK
http://forum.slooh.com/viewtopic.php?t=4931 at Mt Tiede and it can be controlled world wide, and Australia is part of the group. The University of Kentucky is getting one too
http://www.as.uky.edu/academics/depa...servatory.aspx .
Im keeping an eye out for the 1 meter being made now for the California Polytechnic State University, as its about the biggest i know off.
The limiting factor for BIG CDK's is the size of the corrective lens's required, which is why they dont make really big ones. The next biggest i know of is this one 0.7 meter
http://starryridge.com/telescopes/in...p?title=CDK700
I sent an email sometime back to OGS (Optical Guidance Systems) and asked them about the RC vs CDK this is the response i got :
Subject: Re: RC vs Modified Dall Kirham
Dear Theo:
Thank you for your interest in Optical Guidance Systems.
It appears that you already realize that a spherical optical systems is easier to
make. Thus a Modified Dall Kirkham is easier to make to a high precision.
From a design stand point, the MOD is a direct competitor of a Baker Ritchey
Chretien. Both are most advantageous at about f/5 and have huge secondary
obstructions. Both systems will have a flat field with coverage of a 35mm format or
better. OGS has not done an optical design study, but based on what Ceravolo Optics
are saying, it is not diffraction limited over the two degree field, but in practice
it is photographically perfect and easier to collimate.
Our traditional f/9 and f/8 RC telescopes when equipped with a three element
corrector, flattener will provide 1.5 degrees of diffraction limited performance.
You will need a large image area to take advantage of the field coverage. When an f/
8 RC is focal reduced to f/6 or f/5 they will not give a full 1.5 degree diffraction
limited field, but again the performance is still very good.
All of these designs will work well if properly made.
Sincerely:
John Stiles
This email was when i was considering the RC scope.
And yet, still have decided
Theo.
