Newton Rings and CCD Fringing
Posted: Thu May 17, 2018 1:57 am
I'd like to investigate further the incidence of NR and CCD fringing.
This only occurs when very narrow band filters are used in monochromatic light. So, these usually appear in solar Ha imaging.
The NR are caused by interference between the cover plate and the underlying CCD/ CMOS chip. The extent and contrast of the NR can vary camera to camera and are more obvious when larger f ratios are used.
The accepted solution is to either slightly tilt the chip, thereby changing the effective spacing of the cover plate/ chip or by inserting a weak (2 to 4 degree) prism immediately in front of the chip.
CCD fringing, seen in many solar images as a continuous series of well defined lines across the image (much tighter and consistent than the normal NR) are caused by interference within the chip structure.
(See: https://books.google.com.au/books?id=rk ... ng&f=false)
I think it would be useful, and constructive, to record the performance of the cameras we use in terms of NR and Fringing generation.
The data required is straight forward: the camera details, the f ratio used and an example showing the NR/ Fringing.
The DMK 41 and DMK 51 don't seem to have any issues... the ASI 174mm generally shows NR and the ASI 183mm no NR.
What's your experience?????
Either post results here or drop me an email kenm(dot)harrison(at)gmail(dot)com
This only occurs when very narrow band filters are used in monochromatic light. So, these usually appear in solar Ha imaging.
The NR are caused by interference between the cover plate and the underlying CCD/ CMOS chip. The extent and contrast of the NR can vary camera to camera and are more obvious when larger f ratios are used.
The accepted solution is to either slightly tilt the chip, thereby changing the effective spacing of the cover plate/ chip or by inserting a weak (2 to 4 degree) prism immediately in front of the chip.
CCD fringing, seen in many solar images as a continuous series of well defined lines across the image (much tighter and consistent than the normal NR) are caused by interference within the chip structure.
(See: https://books.google.com.au/books?id=rk ... ng&f=false)
I think it would be useful, and constructive, to record the performance of the cameras we use in terms of NR and Fringing generation.
The data required is straight forward: the camera details, the f ratio used and an example showing the NR/ Fringing.
The DMK 41 and DMK 51 don't seem to have any issues... the ASI 174mm generally shows NR and the ASI 183mm no NR.
What's your experience?????
Either post results here or drop me an email kenm(dot)harrison(at)gmail(dot)com