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What kind of film is best for a Vintage Schmidt Cameras

Astrophotography Celestron Imaging Filters
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#1 woodsman

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Posted 01 October 2023 - 07:58 PM

Hi Folks,

 

  I was planning on selling my 8 inch Vintage Schmidt Camera, however I thought perhaps I would hold off and try using it since I never have, and I was hoping to find some others who could give me some tips on what might be the best film to use that is available today. 

 

I plan to mount this on my C14 and I wanted to start with black and white shots of perhaps the Great Nebula in Orion, larger galaxies like the Andromeda Galaxy and maybe the Pleiades. 

 

I live in a very light polluted area and thought that perhaps I could devise a filter system over the film itself to block out a good bit of the light pollution. 

 

I have wratten filters in holders for the film, however I was curious if anyone thought that perhaps placing a larger nebula filter over the film would be possible and if anyone out there has tried this with film.

 

Also, can someone point me in the right direction to find some photos here taken with a schmidt camera?

 

Any assistance would be appreciated.  Thanks!    

 

 



#2 jurdea

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Posted 01 October 2023 - 08:28 PM

I have the Celestron "The Celestron Schmidt Camera" manual and it does make specific recommendations for film, some Kodak, some Fujichrome and some GAF.  Whether they are available or not is another question.  Do you already have a copy?

 

Jim



#3 Michael Covington

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Posted 01 October 2023 - 08:37 PM

The current Ektachrome 100 is excellent as regards both reciprocity and H-alpha response.  I'd suggest you use that (push-processed one or two stops) rather than black-and-white.  I am not aware of a black-and-white film currently available that has good H-alpha response.  For quick tests, to estimate exposures using a film you can develop yourself, I suggest T-Max 100, which does not respond to H-alpha.  



#4 woodsman

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Posted 01 October 2023 - 11:36 PM

I have the Celestron "The Celestron Schmidt Camera" manual and it does make specific recommendations for film, some Kodak, some Fujichrome and some GAF.  Whether they are available or not is another question.  Do you already have a copy?

 

Jim

Hi, thank you for suggesting the book. I do have a copy.  I have both The Celestron Schmidt Camera as well as Celestron Schmidt Cameras. 

 

I know that it states in one of the books that A Red filter which I do have will help with sky fog.  

 

The camera I have also came with the roll film holder so I will try some shots from my home and see if I can't get a few decent shots using black and white film.

 

Thanks for the help.



#5 woodsman

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Posted 01 October 2023 - 11:41 PM

The current Ektachrome 100 is excellent as regards both reciprocity and H-alpha response.  I'd suggest you use that (push-processed one or two stops) rather than black-and-white.  I am not aware of a black-and-white film currently available that has good H-alpha response.  For quick tests, to estimate exposures using a film you can develop yourself, I suggest T-Max 100, which does not respond to H-alpha.  

Thanks, I will purchase some ektachrome and see how the color rendition turns out.  Do you have any thoughts on filtering out the light pollution?  I was hoping that perhaps a wratten type of filter might be available to cut out city Light pollution, but I'm not aware of anything available.  

 

Have a great night, and I appreciate your help!  smile.gif



#6 TxStars

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Posted 02 October 2023 - 09:16 AM

You can process color film as a B&W using B&W chemicals..
Just elevate to the same temp as you would with color chemicals..
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#7 lumière tangible

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Posted 02 October 2023 - 09:40 AM

Hi,

 

I don't know if the books you already have are contained in this : https://www.cometcha...mera/repair.htm

but there is infos about filters in the Modifications to the Schmidt camera's page.

 

I have the 5.5-inch version (that i haven't used yet..) so i'm gathering as much info as i can on it.  I think i saw some images taken with Schmidt cameras here on Cloudy Nights but not sur it was captured on film.



#8 woodsman

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Posted 02 October 2023 - 11:33 AM

You can process color film as a B&W using B&W chemicals..
Just elevate to the same temp as you would with color chemicals..

Thanks, I did not know that.  I'm grateful for the information.

 

smile.gif   Enjoy your day, Rich



#9 woodsman

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Posted 02 October 2023 - 11:50 AM

Hi,

 

I don't know if the books you already have are contained in this : https://www.cometcha...mera/repair.htm

but there is infos about filters in the Modifications to the Schmidt camera's page.

 

I have the 5.5-inch version (that i haven't used yet..) so i'm gathering as much info as i can on it.  I think i saw some images taken with Schmidt cameras here on Cloudy Nights but not sur it was captured on film.

Thank you for the link.  That website has very valuable information on it.  I've been looking through it this morning.  smile.gif

 

Rich



#10 Michael Covington

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Posted 02 October 2023 - 07:02 PM

Thanks, I will purchase some ektachrome and see how the color rendition turns out.  Do you have any thoughts on filtering out the light pollution?  I was hoping that perhaps a wratten type of filter might be available to cut out city Light pollution, but I'm not aware of anything available.  

 

Have a great night, and I appreciate your help!  smile.gif

What type of filter mount is involved?

As for developing color film as black and white, it's probably a good idea to look for published instructions rather than just winging it.  It's definitely something that can be done, and the Ektachrome would have the same H-alpha and reciprocity characteristics as when developed as color.   Another trick is to use D-19 in place of E-6 First Developer to get extra contrast, then proceed with the rest of the E-6 process.

If you're not familiar with Freestyle Sales Co., look them up.  Film photography and processing supplies.


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#11 Todd N

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Posted 02 October 2023 - 08:33 PM

A nebula filter won't ideally perform at the fast f-ratio of Schmidt cameras. Those kinds of dialectic filters are designed to work within certain f-ratio ranges; Usually it's around f/4 on through f/10. If you use them on a a faster system then their bandpass gets shifted to the left of the spectrum. That may end up clipping emission lines and more of the unwanted adjacent spectrum coming through. I tried a LPF filter on a modded DSLR with the lens wide open at around f/2. It produced this color vignetting with a ring of red around the outer perimeter. So, it doesn't even work in that arrangement. Also, mounting the filter inside will change the focus. I imagine the filter glass substrate is thicker than a wratten gel filter. The focus position will change with the addition of any filter mounted internally versus no filter. You'll have to go through the "fun" and tedious process of refining the focus position with successive test shots and film development. If you can find a really light yellow(Wratten2) and a deeper red(Wratten 25) with the same thickness for full spectrum and deep red imaging respectively so, you can change between the two that won't change the focus.

 

With your conditions in mind: light pollution and a fast imaging system, you're going to be limited as to what you can practically accomplish especially since Techpan is long gone. I think you can forget about the blue part of the spectrum. Fuji Acros II has the best performance of a B&W film on the market when it comes to long exposure but it doesn't pick up much of H-alpha. It has very fine grain like Tmax 100. Red filters like a Wratten #25 would work well with this film for broadband objects like star clusters and galaxies to cut the light pollution. I would love to see M31 imaged with this arrangement. 

 

As to chemistry, high contrast developers work well with Fuji Acros lke D-19 or even better Dektol. Dr. Covington mentioned using D-19 with color chemistry process. D-19 can be easily made from bulk chemicals, but one can approximate it by diluting Dektol print developer 2prts Dektol to 1 part water; Same amounts of developing agents as D19 though the other ingredients differ. The convenience of buying Dektol or similar print developer... you'll end up with a gallon of the stuff but it is more inexpensive this way. 


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#12 Michael Covington

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Posted 02 October 2023 - 09:21 PM

Very good points, and they bring back memories!   My other D-19 substitute is HC-110 (A) for 10 minutes at 68 F -- that is, maximum development in HC-110.



#13 JuergenB

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Posted 10 October 2023 - 06:47 AM

As for filters, you definitely will not want to refocus. Therfore, if you intend to switch between imaging with and without a filter, you are limited to Wratten gelatine filters which are very thin and a customised film holder which accounts for the ever so small focus shift of those gelatine filters. They were separately sold by Celestron if I remember correctly.

 

For the Celestron 8" Schmidt, I used Wratten #29 and #92 red filters with 103 aE or hypered TP-2415 (first choice!) film, or CC20M filters with Fujichrome R100 and Ektachrome 100 film in order to eliminate the green cast those slide films usually had.

 

Juergen




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