Perhaps you are still handling the CCD camera as if it were a DSLR. DSLRs are almost always CMOS chips (Nikon used CCDs but now uses CMOS).
They are also heavily amped up with the ISO compared to CCDs (or at least I think so). CCDs do best with long exposure, much longer than probably is feasible with a DSLR. You have to get the signal above the noise sources to be viewable in an image.
They definitely thrive on longer exposure times. I thought my 10 minute subs were a little on the short side but its a balance between exposure, flexure and possible eggy stars.
10 minutes is handy as my dark library only needs to be 10 minutes at 1x1 and 10 minute dark at 2x2.
So I usually use (and so do a lot of others) 10 minute 1x1 for luminance and 10 minute RGB at 2x2. RGB does not need 1x1 as gradations in hue are not sharp like they are in luminance. Some use 1x1 for RGB (I've done this too) for objects where ultimate resolution is important like Globs (where you tend to use shorter exposures like 5 minutes or 4 minutes for Omega Cent or 47 Tuc).
That way you can also desaturate the RGB to turn it back into black and white and add it to your luminance for a bit more signal. I haven't done that much but Marcus did that with his recent lovely image to good effect.
Also aim to do as much exposure time as you can. The really top images you see are usually over 10 hours total. That is not always practical and some images turn out better than others anyway. So on an object you are pretty sure is going to come out nicely (you can tell from the first luminance downloads) it is better to image far fewer objects and for far longer than lots of objects and for short times (I am not that good at this as imaging time can be limited and there are usually several objects of interest to image).
I plan to go for much longer images soon once I move. Perhaps 12.5 hours as normal with the odd 20 hour job on something worthwhile.
Greg.
Quote:
Originally Posted by Paul Haese
Thanks guys for the imput.
Greg the images were 5 minute subs for the Luminance and 25 secs for the colour. Both you and Doug have hit the nail on the head, not enough time at the scope. I do need to check collimation. Although CCD inspector said 4" out, I think it is more than this. Focus was good as I checked this with a Bahtinov Mask and it was perfect, so I think collimation needs some work.
My previous attempts with OSC were pretty good generally but there is a lot to learn I must admit on LRGB. 10 minute subs on all and then shot subs for the core just like OSC.
I thank you for taking the time to respond. Next time I hope to have a better image.  |