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Thanks Greg
Well it seems intuition has served me well Greg. I had been imaging at 20 mins lum and 15 min RGB, but since reading some bits and pieces lately, decided that I could cut a lot of the risk out and still achieve the same result by doing lots of 3 or 5 minute sub then stack them. Well my results doing that did not end up as good as I would have hoped ... the reason for my question today in fact.
Last night I got 54 mins of LRGB of M17 (again) and I really havent achieved much in the way of more signal over the last time when I did one sub each of LRGB at 20mins.
I have realised that imaging clusters for 20 mins is BAD and so like you suggest, its different strategies for different objects. Im yet to try masking areas of nebula' that have saturated stars washing it out and then mixing in a very short exposure of that area to fill it back in again ... knowing how to drive photoshop better will see me through in that regard.
I dont have any problems guiding for 20mins or even longer for that matter and whilst I havent taken a huge amount of shots I have only ever been inconvenienced once by a falling star.
Point taken about the order in which to do the subs, MaximDL's sequencer does it identically to how you suggested ... although I got caught a little last nite because I added a dark in at the ... what I thought would be the end of the sequence, but it snuck it in after the first LRGB shots and so I didnt know if the guide star was still going to be OK, if not how that may effect the position of the subsequent images ... but I must have been lucky and got a reasonable G11 ... because after the 3min dark ... there was less than a .2 error in x and y so it just kept on guiding happily on the same star.
And on a guiding note, there has been another variable ive learnt about of late thrown into the image alignment mix .. field rotation ... like I keep saying ... the answers to one question almost without fail, lead to more questions and so it feels like the information that I need to know to successfully do this imaging is like the universe itself ... expanding !!!
I really do appreciate the feedback I get here from all you folk in the know, thanks very much.
I now know a little bit more about a whole lot more
Jeff
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