Quote:
Originally Posted by Amaranthus
Alternatively, don't worry about star sizes and instead replace them with RGB stars in post processing. It's actually easy to do and quick to acquire.
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Hadn't really considered doing that; I tend to like the more reduced stars you see in narrowband, but that's definitely an idea worth considering. Thanks Barry :-)
Quote:
Originally Posted by RickS
You won't match star sizes just by picking "matching" filter bandwidths. The cause of magenta halos is that most objects are much brighter in Ha than OIII and SII, so you need to stretch the OIII and SII data more regardless of filter bandwidth. You can fix this during processing in a variety of ways.
For Ha, a 7nm (or 5nm) filter will include NII as well as Ha which can be a good thing.
If you can afford it, a 3nm OIII filter will do the best job of rejecting moonlight.
For SII a 5nm should be fine.
Cheers,
Rick.
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Thanks Rick :-)
I've not seen much mention on this forum of doing so, but on CN and SGL it seems to be a very common approach, supposedly for the reason you specify: the theory is that you tend to stretch Ha less so stars appear to bloat in OIII and SII because of the amount of stretching you need to apply. That's the theory anyway, and so people seem to recommend going 5 for Ha and 3 for the others. I was basing my posts above on this.
Thinking more critically about it, maybe it doesn't matter that much. I can probably tweak the star sizes in PixInsight using MorphologicalTransformation, I just wanted to make sure that I wasn't making my life more difficult.