Astro_Bot
06-09-2014, 12:15 AM
This isn't exactly urgent, as I'm taking a break from astronomy for a while, but while it's fresh in my mind ...
TL;DR: How good is Registax or AutoStakkert's stacking in the presence of Alt/Az field rotation?
For an Alt/Az mounted scope, field rotation precludes much astrophotography. But for planetary (or other short exposure) imaging, using a Dob is possible as there's no appreciable field rotation within each exposure.*
However, between exposures field rotation can be significant. For example, in Saturn's recent apparition, in 3 minutes (a typical imaging sequence) field rotation 5 degrees off the meridian was 2.8 deg (or >0.9 deg per minute).
The maths to correct for field rotation is pretty straigtforward so that, for example, in Linux, a script calling ImageMagick routines from the command line can do it fairly easily. Rotated images can then be fed to Registax (from memory, I don't think AutoStakkert takes discrete images).
But is that necessary? Can Registax, or AutoStakkert, handle 3+ degrees of field rotation in a stacking sequence? I realize this would require multiple align points, so that's a limitation. But does it work? Has anyone done that?
* I have no desire to use a field de-rotator for cost and backfocus reasons.
TL;DR: How good is Registax or AutoStakkert's stacking in the presence of Alt/Az field rotation?
For an Alt/Az mounted scope, field rotation precludes much astrophotography. But for planetary (or other short exposure) imaging, using a Dob is possible as there's no appreciable field rotation within each exposure.*
However, between exposures field rotation can be significant. For example, in Saturn's recent apparition, in 3 minutes (a typical imaging sequence) field rotation 5 degrees off the meridian was 2.8 deg (or >0.9 deg per minute).
The maths to correct for field rotation is pretty straigtforward so that, for example, in Linux, a script calling ImageMagick routines from the command line can do it fairly easily. Rotated images can then be fed to Registax (from memory, I don't think AutoStakkert takes discrete images).
But is that necessary? Can Registax, or AutoStakkert, handle 3+ degrees of field rotation in a stacking sequence? I realize this would require multiple align points, so that's a limitation. But does it work? Has anyone done that?
* I have no desire to use a field de-rotator for cost and backfocus reasons.