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That's a sweet image, pops really nice where it needs too, the center has some very good detail. Certainly a good use of 16 hours!
Carl
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Thanks Carl
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16 hours and a good result! Definitely worthy of the main forum. Though that's a phrase often used out of politeness, when you're imaging at your high standard and technical challenge (10-min subs, HaLRGB etc), you want to get some feedback from the top-class astroimagers there.
From my limited experience, I would add a couple of thoughts. First, as already said, the processing is a little heavy, giving the mottled look in the dimmer parts. It might be best to leave a little of the noise rather than going too hard on the noise reduction?
Second things is the quite soft and irregularly-spiky stars. I'm not sure this is a focus issue, and it looks like something I'm dealing with (though on a Newt, not a Cass) - could it possibly be collimation? If anyone else knows what produces these kinds of spikes/flares on brighter stars, I'd love to know too! I'd guess that an ideally set-up SCT wouldn't normally have stars looking so spiky, but apologies if I'm wrong!
But forgive me, it's a minor criticism (as you asked ) of a very fine and deep image indeed, and a lot of time and effort you've put into it!
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Thanks Andy. All good things to point out and work on. I suspect my focus is not there yet. I can't lock my mirror down with the lx90 so there is some mirror flop going on. I'm still fine tuning my collimation. Going to try and get it better with Metaguide when I next get the chance.
Also there may be some field curvature going on around the edges. I think my spacing distance is slightly different than what it should be, due to the focuser. The focal reducer is f/6.2, but plate solving on astrometry.net says it around f/7. All these things may be contributing to some funny star shapes, particularly as you move to the edges of the frame. There could be the odd frame the was accidentally included that had some bad tracking too.
I use Sequence Generator Pro (SGP) as my image acquisition program. It's great! I'm trying to work on an automatic focus routine to re-focus, say every hour, are try and help with mirror flop and temperature changes. I'm getting closer to trusting it some more, but it's a bit tricky with a DC electronic focuser (Meade zero-shift focuser).
I want to run some tests with ccd inspector (trial vs) or MaxPilote to check for collimation and curvature. Still working all that out.
In the mean time I'm collecting more data and will be more careful with my processing. I'll also give the sub-frame inspector script in PixInsight a go. See
here for some useful info that script.
Cheers,
Aaron