Re: [ATM] Large Schmidt Camera?

["tony gondola" <acgna@comcast.net>]

I ran the numbers on that and the primary is way too fast to make it 
worthwhile.......

Tony

----- Original Message ----- 
From: "Joe" <nss@mwt.net>
To: "Dominic-Luc Webb" <dlwebb@canit.se>
Cc: <atm@atmlist.net>
Sent: Monday, April 24, 2006 1:17 PM
Subject: Re: [ATM] Large Schmidt Camera?


> As  something to play with could do a lensless schmidt,,
>
> Joe
>
> Dominic-Luc Webb wrote:
>
>>On Sun, 23 Apr 2006, Michael Peck wrote:
>>
>>
>>
>>>At 14:51 4/22/06, David Sleeter wrote:
>>>
>>>
>>>>Hi Folks:
>>>>
>>>>I have a 16-1/2" dia. F-2.5 spherical Cassegrain-style (hole in the 
>>>>middle)
>>>>mirror, and I'm wondering if there are any off-the-shelf combinations of
>>>>field flattener and CCD camera with which it could easily be used as a
>>>>Schmidt camera?
>>>>
>>>>
>>>Is no one else going to make the obvious reply? To make a Schmidt
>>>camera you need a Schmidt corrector plate. That's going to be the
>>>hard piece to acquire or make. A field flattener by itself isn't
>>>going to help with the 25 waves or so of spherical aberration your
>>>spherical mirror has.
>>>
>>>Mike Peck
>>>
>>>
>>
>>
>>You are of course right Mike. I worry that even the "lensless"
>>Schmidt config may not work, unless maybe the aperture is
>>stopped way down (which I sometimes do on smaller spherical
>>mirrors)?
>>
>>Getting to basics, could the poster confirm that he actually does
>>have an actual "spherical" mirror and not some other (parabola,
>>hyperbola, etc). It makes all the difference in the World here,
>>and we recognize that Cassegrains have different configs. Also,
>>please confirm that the mirror (and not the optical system) is F/2.5.
>>
>>>From there, I would likely go with the corrector plate. For the
>>image surface, I use the glass tool used to grind out a mirror
>>with the appropriate corresponding diameter and curve, and then
>>film. This can be made very quickly with items you already
>>possess for making mirrors. I made my first one in a couple of
>>hours by testing the concave surface with water sprayed on its
>>surface and looking where the light from a lamp came to focus.
>>I just assumed the tool had an equivalent convex curve. I recall
>>that on mine the curvature across a 35 mm stretch diverged from
>>flat by less than the thickness of film, which made me question
>>how important the flattener was. This of course depends on your
>>system.
>>
>>Dominic-Luc Webb
>>
>>_______________________________________________
>>ATM mailing list http://www.atmlist.net/
>>
>>
>>
>>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/ 

_______________________________________________
ATM mailing list http://www.atmlist.net/