Re: [APML] Four Schmidt Shooters

[KGKIRKLEY@aol.com]

In a message dated 5/31/03 1:16:06 AM, tan@cox.net writes:

>Kent,
>
> When I look at the 14" Schmidt camera, I get the impression that a lot
>of
>the issues with it might come from using a separate guidescope for guiding.
>The invar cage appears very rigid but I suspect the whole connection between
>the large tube and the invar cage. Maybe one way is to use a very light
>guidescope such as the e-finder/STV combo, i.e. something which will not
>add
>in weight and cause flexure relative to the invar cage. Of course one must
>get the focus correct as well. The camera is also a two man hoisting job.
>I
>could not do it myself, well not easily at least.
> Another issue with the camera is the lack of a medium format roll film
>holder. If you can build one, it will make shooting numerous exposures
>relatively easy, and you would also not have to deal with processing film
>chips which is a small nightmare as well.
>
>Loke

Loke:
I think the main issue with the Celestron 14 inch f1.7 Schmidt cameras was/is 
the lack of rigidity of the spider-film holder which allowed movement 
resulting in focus shift. If a cast spider were available (like the Epoch upgrade for 
the 8 inch) to replace the tension spider I think the focus problem would be 
fixed.

I think transportation is a problem for the 14 inch Schmidt, because, like 
you said it is a large instrument and would be better off in a permanent 
observatory.

I agree, I think the STV-efinder combination would make a perfect guiding 
arrangement for any Schmidt camera, as their focal lengths are short.

For a number of years I have been using a Vehrenberg medium format film 
holder with my 8 inch f 1.5 Celestron-Epoch Schmidt. Since the holder takes 6x6 cm 
film I had to find/invent ways to handle and process this size film. Due to 
the ink imprinting probems in 1999-2000 with hypered 120 Tech Pan, I switched to 
4x5 Tech Pan cut down to the 6x6 cm size. For storage and transport of the 
6x6cm film I use a 10-sheet 4x5 film box (triple) in which I built a partition 
to hold the 6x6 chips so they were stacked and couldn't move or damage each 
other. I also place a silica gel dessicant pack in the box with the film to 
control moisture. For processing, I use an 'Old-Film-Pack' processing tank. This 
tank is adjustable from 35mm to 4x5 and all sizes in between. Once I found the 
solution to the above problems, using the 6x6 cm film chips is realtively easy. 
This applies to B/W-Tech Pan. I haven't shot any color film this way because 
processing is the problem. Even commercial labs don't have a way to handle the 
6x6 chips. I suppose I could do it myself with the small E6 kits.

The Ash-Lurie camera, which is made in Europe has a medium format roll film 
'back' available. It is a modified Kiev (Russian Hasselblad copy) film 
magazine. The film plane is normally flat, so I don't know how it has been modified 
for the curved film plane of the Ash-Lurie.

Kent Kirkley

 
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