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Celestron Schmidt Camera

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#1 BigC

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Posted 26 March 2013 - 11:48 AM

Well guess who just grabbed a 5.5" model of the long-discontinued item of the title ? :grin:

Now what can I do with it ? :question:

Not sure yet if roll film holder is included.

Has anyone installed a CCD in place of the film holder?

#2 Steve OK

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Posted 26 March 2013 - 01:04 PM

I've wondered about this myself...

Didn't these have some sort of provision to "bend" the film to match the curved field they produced? That would seem to be the downfall of sticking a CCD in there instead of film. Field curvature would do it in. A correcting lens could be employed, then you have a Hyperstar.

#3 gnabgib

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Posted 26 March 2013 - 01:57 PM

There are a few articles online about schmidt cameras and ccd's. If I remember correctly you need to use a plano convex lens just in front of the sensor to act as a field flattener.

#4 highfnum

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Posted 27 March 2013 - 11:06 AM

been there done this I got sc5.5 and sc8
used lodestar ccd

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#5 highfnum

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Posted 27 March 2013 - 11:14 AM

another shot

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#6 orion61

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Posted 27 March 2013 - 07:47 PM

WOW that must have been a Dark spot!
wonderfull..
i miss the old Tech Pan, TriX days when I built a Hypering chamber, We had a local welding company that one guy would
"hand mix" the gas for me, he did a darn good job..
He retired so did my Hyper Kit.. Still have my old Minoltas tho..
It would be cool if someone came out with a Loadable ccd to put in those old Cameras... I know I know it will never happen, or backs were made, but man I loved the feel of those mechanical cameras.. Still get them out timr ti time to actuate the shutters to keep them loose.. SRT102-202 were my favorite..

#7 highfnum

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Posted 27 March 2013 - 08:53 PM

"WOW that must have been a Dark spot!"
eh - NY suburb - 5.4 skies on good day
about 50 sec exposure single unstacked - super fast babies those sc's
thx

#8 BigC

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Posted 30 March 2013 - 10:30 AM

The Schmidt 5.5" was just delivered by Fedex.
Good condition,just a little dust on the bottle,errrr.....mirror.

Corrector plate described as dirty but doesn't look like a problem to me.

No film holder though. :(

Mounting foot on the mirror end and a kind of pin parallel to the tube midway on the bottom ,so some work and ingenuity needed to securely mount this.

I suppose piggyback mounting is usual so the observer and photographer can actually find and see the photo subject ?

Tagged "Arizona Western University" ;, no doubt sold as obsolete.

So now to figure a way to secure a CCD camaera or webcam ,or maybe a Newtonian diagonal on a stalk inserted where the film holder should go? And would I lose the superfast f1.65 by converting to Newtonian system?

Schmidt cameras are new to me .

But couldn't pass up this chance for fast optics.

#9 BigC

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Posted 30 March 2013 - 10:52 AM

After reading some online info, the conversion to Newtonian seems to have advantages of getting camera body out of the light path ,camera heat out of the tube ,and possible allowance for easier experimentation of filters and flattening lense.

Since there is no free lunch,what am I overlooking?

#10 highfnum

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Posted 31 March 2013 - 04:57 AM

Newt idea not so good
Fl won't make out door unless barlowd
Plu cone is wide
Do you have vane fins in tube?

#11 highfnum

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Posted 31 March 2013 - 06:26 AM

her is my 5.5 mod

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#12 BigC

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Posted 31 March 2013 - 11:02 AM

Excuse me for density but all I see is a vinyl lens cap?.

I guess there is a camera there.What keeps it in place?

The vanes and machined cylindical piece are in place in mine ,just no actual film holder.No doubt the film holder(s) were in another box at the auction.

#13 highfnum

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Posted 31 March 2013 - 11:22 AM

Yes lens cap on camera
If you look behind cap
You can see body
Held by simple pressure
Rubber strip added to vanes
Thst is why I chose lodestar
Almost exact size
I got bw and color

#14 highfnum

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Posted 31 March 2013 - 11:25 AM

Oh cylinder removed

#15 highfnum

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Posted 31 March 2013 - 06:02 PM

i suggest go to robert reeves astrophotography web site
he was grand master of sc camera
sc have internal reflection issues
this is normal but annoying
here is example

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#16 Starman27

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Posted 01 April 2013 - 08:57 AM

Excellent mod.

#17 highfnum

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Posted 02 April 2013 - 08:56 PM

Thx
BigC I suggest you read
Adventures with mr schmidt telescopes
By David H Levy (star trails)
He explains agony and ecstasy of using
Camera
3 years to focus with film

#18 highfnum

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Posted 02 April 2013 - 09:11 PM

here one more

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#19 Giorgos

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Posted 05 April 2013 - 01:03 PM

A schmidt camera without a film holder is virtualy useless... Film holders were manufactured to match with every specific schmidt camera and are NOT interchangeable (you can't use a film holder of another schmidt camera of the same aperture) the focus will be off. Using the lodestar the focus isn't perfect either because the focal plane of a schmidt is not flat. Also the chip of the lodestar is much smaller than a 24x36 mm frame so you will lose the large field characteristic of the schmidt design. I have tha same camera with 3 film holders but I plan to use it with black and white film that I will develop myself.
If you get a spare film holder and IF (yes a big one) you adjust the focus successfully (a long and tedious process) then you will have outstanding results. Far better than with small CCDs like lodestar. Fuji acros doesn't need any hypering and with any film the short exposure times with superfast schmidts reciprocity failure is not much of an issue.

#20 highfnum

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Posted 05 April 2013 - 05:21 PM

Yes in theory. Your argument is correct
But the reality
I got pictures
I'm still waiting to see some film shots
From any one since 1990's

#21 mitsos68

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Posted 16 April 2013 - 12:10 AM

Hi,
b/w films are still available, and still with good characteristics. Cost structure for film imaging with SC is superior in comparison to CCD. Not to mention that the film equipment is far more portable. Nevertheless CCD addition to SC is an interesting approach.

#22 highfnum

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Posted 16 April 2013 - 02:36 PM

It the focusing of film thats the hard part

#23 highfnum

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Posted 16 April 2013 - 02:52 PM

Professional sc observatories have replaced film with ccd
Of course their ccd are real large

#24 mitsos68

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Posted 16 April 2013 - 11:08 PM

Indeed, but there is a good number of focused instruments out there and if the SC is an Epoch one with a one piece stiff spider installed then the focus can be considered permanent. In pro level the CCD offers linearity,broad spectral sensitivity etc but we remain amateurs after all. See the one piece Epoch spider.

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#25 mitsos68

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Posted 17 April 2013 - 08:42 AM

Hi,
I know that Robert Piekiel modified at least one 5.5 Celestron Schmidt and at least one 8 Celestron Schmidt to Newtonian configuration by:
1. Opening a 2 inch hole in camera's door
2. Adding a screw type focuser.
3. Adding a PVC pole with a elliptical type diagonal on the magnetic film holder of the camera.
As a result he could "see" the image few mm above the reflective diagonal surface.
I think that Robert is a member of Cloudynights community, so you can reach him for additional information. See a relevant picture below.
Of course the curved field remains. So, this would be a nice challenge for the dedicated amateur. To find a combination of a 50mm diameter relay lens that can send the converging rays out of the tube with field flattening properties. A dedicated SC field flattener should be typically a plano-convex with the convex side (facing the mirror) having a radius of curvature, R, given by:



R = F(n–1)/n



where F is the focal length of the Schmidt camera, and n is the refractive index of the glass used for the field-flattening lens.
This lens should placed as close as possible to the CCD face. For the SC users in the US with the skilled ATM community I thing that the article below is very useful:

http://www.britastro...di/harlow01.htm

Personally, I believe that SC are still alive and potent instruments.

Clear skies.

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