What should I use as the default maximum dither in pixels? AstroKam will then calculate a random dither for each axis based on this maximum.
Good question. Maximum dither depend on:
- guide camera resolution (arcsec/pixel), if dither too low, nothing happen
- guide camera field of view /vertical and horizontal/ (arcmin) if dither very high, guide star lost
- main camera resolution (arcsec/pixel)
- main camera field of view /vertical and horizontal/ (arcmin)
- main camera ccd type (DSRL cameras better than small compact cameras)
- main camera distortion (barrel, pincushion, wavy) big zoom = more problem. If error big, cannot process the frames properly to final image.
There is good software for correct distortion error called hugin, but it is not astro software and i don't know any astro software that has it. Deep sky stacker has common problem, regim better, but does not have special distortion corrections. All these software are freeware.
I think the maximum dither parameter will have to be user variable. I do not have good value for this yet. Requries lots of real sky test. I live in big city = bad sky. Astro camps are the real alternative, i go there in two weeks time. I made test shoots that show the problem, but without dither there are lots of non movable noise in the dark frames. Way worse than DSRL.
My small portable mount is homebrew modified (lx200 emulated stepper motor drive) only support right ascention guiding. So, I think it would be great to have two versions one with RA dither only an other one with full RA and DEC dither. I have acces to larger amateur full computer controllable telescopes but those are not mine.
The random dirther is a good idea. The goal would be for the area to be evenly covered. Another good mode would be the square helix line. Good value range 0.01 - 99.99 pixel. Lots of users use both methods. I guess 2 pixel would be a good default step for example. If sub pixel guiding is supported then value sould be float pointing value.
