Niall MacNeill
Member
I have been processing my captures of NGC 6744. All was going well until it came to the Green channel. All the Registered Lights have a background ADU of ~ 110-120. The MasterStack however had a background ADU level of ~ 14. How does the integration of images end up with so much lower a background ADU than the individual subs. None of the other colour channels were affected. Note I added a pedestal of 100 at the time of calibration. I wondered if this would occur for a smaller range so I split it into two. The 2nd half when integrated gave me ~ 175 ADU, but the first half of the Register Lights gave me the 14. And so I honed it down. Eventually by going backwards and forwards it seems to be down to one sub, which if included gave a low background ADU. So then I selected everything and excluded that sub. You guessed it, the background ADU was still 14. I tried excluding one or two each side....same result. In the end, I chose from about 3 subs after the one I found to be suspect and then selected the remaining subs, some 60 in total and the final result came out with a background ADU of 175.
I am quite perplexed. Any ideas?
Regards, Niall
I am quite perplexed. Any ideas?
Regards, Niall