Light Frames calibration

[GregF]

Fairly new to PixInsight and Astrophotography so may be a dumb question. I have a SBIG STX 16803 and have  just started building a library of dark frames. A couple of questions. Do i really need to build a library or could i just take 50 dark frames at 1800 seconds and when i calibrate my light frames be they 600 seconds, 900 seconds or whatever the length just click the optimize tab or is it better to make dark frames the same length as the light frames but still optimize for slight temp differences. Also all darks and lights will be at -20 so its not the temp i am wondering about but the time difference.

Thank you

Greg

[pfile]

as long as you don't have amp glow or RBI turned on you should be able to scale the darks as you are describing. but you will need a master bias in order to do that.

rob

[GregF]

Thank you. I did create a master bias with 500 frames and then created a super bias. I just noticed that there are several options for creating the super bias (columns, rows, or both). Which are you supposed to use. Also to the original question, is it better to optimize in the way i asked, is there a difference in making the darks the same length or will the results be the same? Thanks again

[RickS]

If you have 500 bias frames then a super bias is probably unnecessary, but the "columns" option is almost certainly the right one for that sensor (does it look like any structure in the frames is column based?)

I've used matching length dark frames and also long dark frames with scaling/optimisation and both work adequately.  If you have the time to do matching darks then I think you'll find that works a little better for the small percentage of pixels that behave especially strangely.

Cheers,
Rick.

[GregF]

Thank you for your help. This is the 500 frame bias and below is the super bias using columns.

[GregF]

Well that didn't work, let me try again

[pfile]

you would need to stretch the images so they are visible as jpeg.

at any rate with a 500-frame bias i would not bother with a superbias. it can be a little tricky to make a SB properly...

rob

[GregF]

I was able to convert to jpeg using a script from Ip4ap but the file is to big to post. The 500 frames and the super bias both look almost the same. Thanks again everyone for the help.

[ngc1535]

Just as a single data point- I have been using long (1800s) scaled master darks to calibrate all data (exposure times) for the past decade.
It think it is time saving strategy that works well. The major thing to understand is that a population of hot pixels that does not calibrate out is not a testament to a poor (long)
master dark. This is to be expected and will be taken care of with the combination of cosmetic correction (hot pixel removal) and statistical rejection as long as all-important
dithering took place.

So a big thumbs up from me.

-adam

[GregF]

Thank you all again for the help, it is much appreciated.