Quote:
Originally Posted by luka
There is a detailed description of the effect of stacking on the noise on the DSS page here.
Simplified, if you double the number of images your SNR goes up by sqrt(2) = 1.41x.
Triple it to get SNR up by sqrt(3) = 1.73x
4x imaging time will get you double SNR.
(SNR = signal to noise ratio)
Chris, the lack of improvement could also be due to quality of data. Perhaps on the 2nd night the seeing was not that great or your guiding was not spot on etc. Also if you are trying to image from light-polluted areas, unfortunately you will never be able to get the faint signals. And you have processed the data from two nights differently... in theory that should not matter but in practice who knows  |
Thanks. I'll go through my single images. The quality was a bit variable. And I have some guiding issues - still learning how to do that in phd2. There's a big slow sine wave (1-2" peak-to-peak) on the RA guiding - I can see that it's spread my stars in that axis so it must do awful things to the DSOs. So sorting out pec is next. Doing that while the moon is around. I'm trying the inbuilt pec on the cgem, but has anyone used the beta phd2 with the built in pec? I tried it last night and it actually seemed to work after a few cycles.
It's all a massive learning curve.