Does stacking of rotated DS frames from dobson mounts work?

Anders
23 Apr, 2018 15:27
Have a 10" Skywatcher Dobson.
Anybody who knows whether DS frame series will be "de-rotated" automatically by stacking software? In that case, which SW is the preferred one..?
Hope anyone could give some advice smile
zishor
23 Apr, 2018 18:03
Hi yes this will work but you will lose some field of view. Try out AstroPixelProcessor, it also comes with a great dynamic distortion correction.
Best Frank
micvon
23 Apr, 2018 19:00
Pretty much any stacking software will derotate your images (I use DeepSkyStacker, very basic, but it works well). You have to be careful in limiting the exposure time of each frame up to no more than 30-60 seconds, otherwise you will have field rotation within each image, i.e you will see star trails.This is because your telescope has an alt-az mount and despite the fact that it can follow the movement of an object at the centre of the field, everything else will have an apparent motion. Below 30-60s exposure this effect is negligible (sort of), the real amount of field rotation depends on the azimuth and altitude of the object you are imaging, as well as your latitude. In a nutshell, objects below 30 degrees altitude and towards east and west are relatively safe = no appreciable field rotation even with long exposure time (you can probably dare with exposures of 2-3 minutes). The more your objects approach north and south and the higher in the sky they are, the more you are in dangerous zone, with fast field rotation..it is all very well explained here : http://calgary.rasc.ca/field_rotation.htm . As pointed out by Frank Schmidt because of field rotation your stacked image will have large non overlapping areas (i.e your initial composition will vary over time), so in the end you will have to crop the stacked image to remove the areas that do not overlap, and your final image will be smaller than your initial field.
Hope that helps.
zishor
23 Apr, 2018 19:26
Thumbs up for your explanation Michele! Also the link to the field rotation explanation is amazing!
micvon
23 Apr, 2018 22:30
Frank Schmitz
Thumbs up for your explanation Michele! Also the link to the field rotation explanation is amazing!
Glad you liked it!
Anders
05 Jul, 2018 09:33
Thanks a lot for valuable feedback.. 👍👍👍
lock042
05 Jul, 2018 17:31
If you want very powerful and free (opensource) software, you can take a look here: https://www.siril.org
It is now possible to automate the process by using script !!
 
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