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CCD inspector

Posted: 16 Jan 2020, 11:25
by heno
Hi
Can anybody tell me what the curvature figures (negative/positive value) means? In which case should I move the camera further away from the scope?

Thanks
Helge

Re: CCD inspector

Posted: 16 Jan 2020, 13:37
by han.k
Hello Helge,

The curvature value is only indicating that the stars shapes in then center of the image are smaller then at the outer areas. That can be due to wrong corrector distance or simple due to optical laws that the star shapes further away from center get a little oval. Any curvature indication below maybe 15% is normal.

The only way to find the best corrector distance is to try it out. ASTAP can help to measure the differences. Use a star rich field for testing. Or to calculate using a formula and set it using a measure tape.

Han

Re: CCD inspector

Posted: 23 Jan 2020, 11:46
by heno
Thank you Han.
The curvature figures are not dramatic and probably to live with, although they varies a lot. This is a RASA 8 scope. I may try to insert a thin spacer to increase the distance to the camera and see where that takes me, but reducing it would mean to buy a new, shorter filter drawer. That is not an option and I probably could not find one anyway.

Helge

Re: CCD inspector

Posted: 23 Jan 2020, 11:56
by han.k
Hello Helga,

In ASTAP latest version 0.9.315, I added some extra numbers to the screen and the tilt & curvature is now expressed in delta hfd values.

There is also a new inspector tab but that's becomes very technical. See:

https://www.cloudynights.com/topic/6905 ... try9928932

or here:
https://stargazerslounge.com/topic/3473 ... each-area/

Clear skies, Han