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Photo

M31 taken with Celestron 5" Schmidt Camera f/1.6

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#1 svenk123

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Posted 12 September 2019 - 01:01 AM

Hello,

 

I am amazed about this very fast optic. After digital modification this is one of my first test images showing M31, the Andromeda Galaxy.

The total exposure was only 30 minutes (60x30s) and most of the stars were clipped at 30s sub exposures. The camera inside the SC is a ZWO ASI183MC.

 

Thanks for looking.

  Sven

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#2 james7ca

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Posted 12 September 2019 - 03:05 AM

I think I've read about these old Celestron Schmidt cameras but I don't think I've ever seen an image from one. Thanks very much for posting.

 

Looks plenty fast although even at this reproduction scale I think I can see distortion in the stars. However, the upper left quadrant looks better, so I wonder whether you have tilt in the camera system. The colors look good and it's certainly a fine looking image for only 30 minutes of integration time.


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#3 ngc7319_20

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Posted 12 September 2019 - 03:11 AM

Did you install some lens near the sensor to flatten the field?  These originally use a film holder with a curved surface.


Edited by ngc7319_20, 12 September 2019 - 03:12 AM.

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#4 svenk123

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Posted 12 September 2019 - 03:01 PM

Yes, there is still some sensor tilt. Tilt adjustment is very tricky at this focal ratio. Focusing and tilt adjustment is

one of the main steps befor starting an imaging session. Something i have to optimize in the future.

 

I have removed the cameras AR window and put a planoconvex lens onto the sensor chip to flatten the curved field.

Only one lens is not optimal and introduces a terrible inverse coma. I had to shorten the tube about 3,5 cm to move the corrector, this defeated the coma.


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