Quote:
Originally Posted by Shiraz
Thanks Mike. Yep, I like the SX camera a lot - to the point where I do not think about it much anymore - It just seems to work very well regardless and results will be determined by other factors (eg seeing). As for it being an alternative to the 8300, I think it is different enough to have its own niche. Where you want high resolution imaging from short focal length scopes and in conditions where long exposures may not be possible (particularly using Ha), the icx694 is in a league of its own. It costs a bit more than an 8300, but I think that the extra performance could be worth it in many cases.
FYI, have been trying a range of pre-processing techniques and have got the best possible SNR by doing an initial hot pixel removal from darks and lights - before the normal calibration process. The read noise of the chip is so low low that it doesn't mask the minor noise that results from dark subtraction where the thermal noise is significant (hot pix). Getting rid of a few hundred warm/hot pixels first is worthwhile. Of course, this extra effort is only beneficial if you are digging around in the depths of the data for tiny signals - on most targets it wouldn't matter at all.
Regards ray
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I had never done it before with my previous SX and FLI cameras but initial results with the H694 suggest that dithering and then median combining takes care of everything and prevents any noise being added by dark subtraction. It's pretty cool to watch on the screen too, when the guide star gets moved around and locked onto again
This (full frame full resolution) is a median combine of 6 X 5min dithered sub frames, no darks and no flats (of course it is pushed quite hard to reveal as much as possible from just 30min). NB the pause after dither move was not long enough and half the subs started before the guide star had been fully re-acquired and this showed slightly in the star shapes. Since this, Fabio from MSB Software (Astroart) has rewritten the camera control code to lengthen this pause for me
No Darks and no Flats!
Easily Amused Mike
