Quote:
Originally Posted by PRejto
Hi Ray,
I appreciate your comments as always.
Firstly, I have not figured out how to dither two scopes at the same time especially since I'm often taking different length exposures. But, even with the same exposure I can't quite see how to do it given the differing download times of the two cameras (the Trius is fast and the G2 slow). But, I know dithering would really help the noise so I'd like to attempt some sort of solution.
As for darks, bias. flats. Currently I'm taking 40 bias, 20 darks, and 50 flats. The flats have a mean adu of 33,900 with a min= 9,600 and a max = 52,158. Should I be looking for an mean that is lower given that max value? I've generated all of my calibration frames in CCDStack. For rejection during stacking I use the Standard Sigma Reject for luminance when I have a lot of subs, and the Poisson reject for RGB. If you have another suggestion please let me know.
So, if I've got this right the issue in LP is the decreasing (with time) of the dynamic range of the camera. And, it's the dynamic range that allows the real signal to be seen over the noise. But, I think I can safely say that 10 1 min subs will not give the depth of a single 10 min sub. Getting the balance just right between those two extremes is the tricky bit.
Many thanks,
Peter
|
Hi Peter
Haven't tried it, but I think that multiple sessions of Maxim can be synchronised to enable dither with multiple cameras.
http://www.youtube.com/watch?v=dmqxgDJBmX8
FWIW, I used to use 25 darks with my H694, but found that it needed a lot more - dark noise can be imprinted on the flats and that can lead to noise that does not reduce with extra exposure. With heavy LP, I would guess that at least 50 darks would be needed - maybe even more. I would also use maybe 100 bias and flats (33900 should be fine for the flats, but 52000 may just possibly be getting a bit close to the non-linear region of the CCD). If the LP is severe, you might even get some advantage from even more flats. Of course dither will fix most of the noise if you can get it going.