Using SC4to counter image drift
Posted: Wed Apr 07, 2021 5:06 am
So this is a very specific situation.
1. Sky brightness at 17 or so (maybe 17.5 - 17.8 late at night if I'm lucky). So very short exposures
2. Restricted sky view between buildings. Polaris not visible. So polar alignment accuracy is limited.
So I can take several subs of max 10-15 sec each (which is incidentally very long for the sky brightness). But over a period of time, the inaccurate polar alignment results in the image drifting between subs.
My solution is to re-align every 5 minutes through a simple sequence like this
1. Plate-solve and sync the target
2. Wait 15 sec for mount to settle down
3. Take 20 subs of 15 sec each
4. Loop steps 1-3 till desired integration time is reached (in this case, looping 12 times will result in total integration time of 1 hour).
This works superbly. My sub rejection has dropped sharply and the stacked pictures have much fewer artifacts at the edges, needing less cropping. Of course, the specific numbers will vary with the mount and sky conditions.
Thanks to Robin for making this possible.
1. Sky brightness at 17 or so (maybe 17.5 - 17.8 late at night if I'm lucky). So very short exposures
2. Restricted sky view between buildings. Polaris not visible. So polar alignment accuracy is limited.
So I can take several subs of max 10-15 sec each (which is incidentally very long for the sky brightness). But over a period of time, the inaccurate polar alignment results in the image drifting between subs.
My solution is to re-align every 5 minutes through a simple sequence like this
1. Plate-solve and sync the target
2. Wait 15 sec for mount to settle down
3. Take 20 subs of 15 sec each
4. Loop steps 1-3 till desired integration time is reached (in this case, looping 12 times will result in total integration time of 1 hour).
This works superbly. My sub rejection has dropped sharply and the stacked pictures have much fewer artifacts at the edges, needing less cropping. Of course, the specific numbers will vary with the mount and sky conditions.
Thanks to Robin for making this possible.