Substitute Master Bias for Darks

[Martin Dowd]

I image with both the 2600MC and 2600MM cameras and have never needed Dark frames ( most folk dont either ) Ive used Flats and Bias for calibration successfully with Deep Sky Stacker for many years now.
Just recently Ive switched to ASTAP for Stacking which had worked well so far.
Ive been loading my Master Bias in "Flat Darks" , loading my Flats in "Flats" ( then create a Master Flat ) , then load my Master Bias in "Darks" . Substituting Master Bias for Darks was suggested to me by an ASTAP user on another forum.
Please advise if substituting Master Bias for Darks is OK in ASTAP ? or should I just leave "Darks" empty ?
Thanks in Advance
Martin
PS: I use Startools for post processing , so all my stacks are individual stacks per filter ( LRGB for Broadband and Ha Oiii Sii for Narrowband ) stacked and aligned ready for loading into the individual filter channels via Compose Module in Startools.

[Martin Dowd]

Found my answer through trial and error experimenting as follows -

1/ When I load my Bias frames in Flat Darks tab, load my Flats frames in Flats tab, leave Darks tab empty, load Lights then Stack using Sigma Clip average ( improved ) the resultant image has a type of inverse vignetting ( bright perimeter and darker centre ) This effect varied in intensity from Red to Green to Blue filter. Also tried a Ha data set whichb resulted in a type of reverse or inverse vignetting.
2/ When I leave Flat Darks tab empty , load Flats frames in Flats tab, load Bias frames in Darks tab , load Lights then Stack using Sigma Clip average ( improved ) the resultant image has a perfect flat field .
3/ When I load my Bias frames in Flat Darks tab, load my Flats frames in Flats tab, load same Bias frames again in Darks tab, load Lights then Stack using Sigma Clip average ( improved ) the resultant image has a perfect flat field.

Comments welcome

[han.k]

i'm traveling.
quick answer. Option 3) is a good option. bias instead of datk in the darks tab. but it is better to put datks in darks tab. keep all tabs filled. but bias i an accetable subtite of darks. note that the masterflat will contain the bias once prcessed

Han

[Martin Dowd]

Han,
Thanks for confirming that arrangement
Appreciate your reply whilst busy travelling
Martin