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Old 19-12-2008, 03:24 PM
Ian Robinson
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Spotted an 8" Celestron Camera

http://www.cloudynights.com/classifi...&cat=15&page=1

only wants 1500USD , tempted but if I buy it I can't :
- afford to build my ROR observing shed
- afford to buy that Ef 70-200 f/2.8 L IS USM and 2x TII EF teleconvertor.
So I'll pass.

Maybe someone else here might be interested in it. It's in the USA and owned by a uni .

I have a sneeking suspiction there is still one for sale here in Oz too.

Someone cleavour with optics could probably make field flattener for it and use it with one of those very low footprint highish pixcel count CCDs from Starlight Express and make it a superb wide field and very fast imaging camera.
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Old 19-12-2008, 03:57 PM
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Quote:
Originally Posted by Ian Robinson View Post
http://www.cloudynights.com/classifi...&cat=15&page=1

only wants 1500USD , tempted but if I buy it I can't :
- afford to build my ROR observing shed
- afford to buy that Ef 70-200 f/2.8 L IS USM and 2x TII EF teleconvertor.
So I'll pass.

Maybe someone else here might be interested in it. It's in the USA and owned by a uni .

I have a sneeking suspiction there is still one for sale here in Oz too.

Someone cleavour with optics could probably make field flattener for it and use it with one of those very low footprint highish pixcel count CCDs from Starlight Express and make it a superb wide field and very fast imaging camera.
The 70-200 F2.8L IS is definately a nice lens i use it for most my photography and im planning on a teleconverter soon...if yours is dedicated for astronomy stuff though you might want to consider a 400mm prime F5.6 its a bit cheaper and id say it will be sharper than a L zoom lens with a 2 x converter

But hey a 2 x teleconverter might not be that bad if your using a crop body
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Old 19-12-2008, 04:08 PM
Ian Robinson
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Originally Posted by aokman View Post
The 70-200 F2.8L IS is definately a nice lens i use it for most my photography and im planning on a teleconverter soon...if yours is dedicated for astronomy stuff though you might want to consider a 400mm prime F5.6 its a bit cheaper and id say it will be sharper than a L zoom lens with a 2 x converter

But hey a 2 x teleconverter might not be that bad if your using a crop body
Mine will be a general lens , not just for astroimaging.

Will be pretty handy on my 40D (which is "a cropbody").

Last edited by Ian Robinson; 19-12-2008 at 09:00 PM.
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Old 20-12-2008, 12:43 AM
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Ian I have one, I got it from the Neatherlands of all places for $800 us. I am converting it to ccd and adding a field flatener. As luck would have it if I use BK7 glass I can use off the shelf optics with the right radius. The project has stalled abit due to other things going on as well but it will be done on day.
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Old 20-12-2008, 01:53 AM
Ian Robinson
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Originally Posted by KenGee View Post
Ian I have one, I got it from the Neatherlands of all places for $800 us. I am converting it to ccd and adding a field flatener. As luck would have it if I use BK7 glass I can use off the shelf optics with the right radius. The project has stalled abit due to other things going on as well but it will be done on day.
Lucky man .... when done it will be great imaging scope .... where's that "Green with envy smiley" ?

Looking forward to reading a detailed account of the conversion and optical upgrade some time in the future and seeing some images (all here at IIS I hope, though it would be something S&T would probably like too.

These things keep on showing up for sale it seems , I've seen 3 or 4 (mostly the 8" version) over the last year or so at Ebay , and Cloudy Nights and other places.

I think there is a commercial version of what you are doing too that incorporates a Starlight Express CCD camera, is your conversion similar.

Last edited by Ian Robinson; 20-12-2008 at 02:04 AM.
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Old 20-12-2008, 02:49 AM
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Yeah similar but fixed focus. I talked to Robert Reeves for some advice he wrote Wide-Field Astrophotography and has a good website about the camera. http://www.robertreeves.com/repair.htm
There was another page which I got may Idea from but it seems to have gone. Your right these do come up ever now and then, they made a 5 and 8 and a 14 inch version would love to get the 14. I have also seen a site that shows you how to mod a meade schimdt-newt which makes to focal plane easy to get at.
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Old 20-12-2008, 09:01 AM
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I think I read that APM were making a CCD version of this. Also one was on sale here in Australia not long ago for about 800AUD so 1500 seems a bit much.
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Old 20-12-2008, 10:04 AM
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How would you adapt this for digital photography
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Old 20-12-2008, 12:14 PM
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As you know a F1.5 has a very curved focal plane. The camera was designed to be used with film that was curved to the focal plane via a film holder. CCD are very flat so the only way to do it is to use a field flatener. Now as long as you put the lens very close to the focal plane then very little aberrations are introduced.
A signal panoconcave lens is all that is needed.
Now Telescope Optics by Rutten and van Venrooij tells me the required curvature is calculated by
R= (f(n-1))/n where n is the refractive index of the glass
For a F1.5 system using BK7 glass
R = 300(1.52237 -1) 1.52237 = 102.93
I think 100mm would be good enough, this is a off the shelf item.
I will use a APS size ccd this shouldn't be to taxing for it. I will test and If need be get a custom lens made.
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Old 20-12-2008, 01:45 PM
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Quote:
Originally Posted by KenGee View Post
As you know a F1.5 has a very curved focal plane. The camera was designed to be used with film that was curved to the focal plane via a film holder. CCD are very flat so the only way to do it is to use a field flatener. Now as long as you put the lens very close to the focal plane then very little aberrations are introduced.
A signal panoconcave lens is all that is needed.
Now Telescope Optics by Rutten and van Venrooij tells me the required curvature is calculated by
R= (f(n-1))/n where n is the refractive index of the glass
For a F1.5 system using BK7 glass
R = 300(1.52237 -1) 1.52237 = 102.93
I think 100mm would be good enough, this is a off the shelf item.
I will use a APS size ccd this shouldn't be to taxing for it. I will test and If need be get a custom lens made.
That's probably all that happens in those Celestron Faststar assemblies that were being touted as the bee's knees a few years ago.

Will that corrector also correct for coma ? I imagine it would be severe at f1.5

I was aware of 5" and 8" versions , didn't know about (or forgot) the 14" version , I thought they also had an 11" version too.
The 14" version would be a stupendous catch once modded and corrected for flat field coma free CCD imaging .... they'd be rare as hen's teeth too.
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Old 20-12-2008, 10:43 PM
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Ian the Faststar attachment had more then that in them I hope as the corrector plat is in the worng spot. Same with the meades that's why you can fix them up by moving it to the right location.
The idea of a schimdt is to have no coma, The simple lens shouldn't introduce any/much, but I guess I'll find out.
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Old 21-12-2008, 01:35 AM
Ian Robinson
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Originally Posted by KenGee View Post
Ian the Faststar attachment had more then that in them I hope as the corrector plat is in the worng spot. Same with the meades that's why you can fix them up by moving it to the right location.
The idea of a schimdt is to have no coma, The simple lens shouldn't introduce any/much, but I guess I'll find out.
That was interesting - it's a wonder more people don't mod their SNTs and SCTs.
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Old 21-12-2008, 01:54 AM
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Ian : what are you referring to when you say mod the SCT/SNT scopes? adding a field flattener?


I wonder if it would be hard to make/buy a flattener for my C11 to be used at F/10... The 6.3 reducer/corrector flattens the field nicely, but also drops it back to F/6.3... F/10 + flat field would be nice...
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Old 21-12-2008, 09:53 AM
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Ian : what are you referring to when you say mod the SCT/SNT scopes? adding a field flattener?


I wonder if it would be hard to make/buy a flattener for my C11 to be used at F/10... The 6.3 reducer/corrector flattens the field nicely, but also drops it back to F/6.3... F/10 + flat field would be nice...
No - taking the optics out and reconfigering them in new tube to make truely fast schmidt cameras (f1.2) alomg the same lines as Kevcool's camera (after respacing the corrector and primary and installing a field corrector lens and small footprint CCD camera at the primary's prime focus.
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Old 21-12-2008, 10:48 AM
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oh... Yeah... a lot of people wont do that, due to the fact that they bought the SCT to get the long focal length, converting it to F/1.2 (my C11's primary is 1.8) sort of defeats the purpose...

I have thought long and hard about converting the C11 to an open truss setup before... However the tolerances of an SCT system are much lower than that of a newtonian... you'd have to make the truss PERFECTLY the right size...

Not to mention that getting 8~10 carbon fibre truss tubes would not be the cheapest of ventures..
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Old 21-12-2008, 10:48 AM
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I have a mint condition 5.5" F1.65 Celestron Schmidt camera in case with extra film holders inc Wratten 92 focus corrected and roll film holder, heated dewcap with incorporated lightweight shutter system.

I'm pretty lazy when it comes to shifting unused /unwanted gear. If anyone wants to talk me into parting with it for a fair price then PM me.

I'm not sure what it would be used for these days but I used to use tech Pan and also 3M 400ASA slide film with great results.
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Old 21-12-2008, 06:57 PM
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some links of interest
Moded Meade http://www5f.biglobe.ne.jp/~kztanaka...idtcamera.html
homemade schmidt conveted to ccd.
http://www.ast.cam.ac.uk/~ipswich/Te...chmidt_CCD.htm
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Old 06-01-2009, 07:49 AM
prenzi (Florian)
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Modification of 8 inch Schmidt camera

Hi Kenny,

I have the pleasure of owning one of the fabulous 8 inch Celestron / Epochs as well and would be interested to learn whether you indeed have succeeded in modding your camera from film to CCD. Had the same idea, but so far have not been able to find someone who could give me some hints on how to do this, where did you get the lens from, at what specs, etc etc. My idea initially was to use one of the big chips with film size, but I might have to downsize due to costs - unless someone on the forum has one of these lying aroung and intends to get rid of it at an affordable price....

We live rural in the Northern Adelaide Hills, so seeing is quite good, a digitized fast Schmidt would do wonders here....

Thanks in advance for your help and advice, all the best and cheers,

Florian
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Old 06-01-2009, 05:39 PM
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Smaller CCD means you dont have to worry about a field flattner. A bigger chip will require some correction to match the curved field.
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Old 07-01-2009, 12:32 AM
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Hi Florian,
Sorry haven't been watching this thread, Netwolf is right if you are using a small chip them you don't need a flattener, however what then is then point. The camera is made for a wide field use it. The main mod is the spider it needs to be changed so you can put the camera in. Mine will have the camera in all the time, this should make is simple. The lens can be got form many places a quick google will find heaps. Read the above for the specs, the lens will work best the closer it is to the sensor. BTW this project is but one of many I have sort of going, so it may be some time before I get a round to it. I had planned to use it for comet and nova patrol but a the moment I'm having fun taking pretty piturs with my 132mm refractor and 250 RC. ah but one day...
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