Quote:
Originally Posted by strongmanmike
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 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  |
Thanks for the info Mike - I guess that method also uses a non-linear process to get rid of hot pixels and it overcomes residual fixed pattern thermal noise by spreading it around - will give it a go. I have not tried to use dithering yet with the H694, even though phd/Nebulosity supports it - I have been wary of having the EQ6 deliberately go off target, since it can take a long time to guide back on accurately enough at ~1 arcsec/pix and 2-3 second tracking loop update rate.
The image you linked to sure is a good illustration of just how quiet these chips are.
Regards ray