Quote:
Originally Posted by gregbradley
Really a very lovely NGC300 which is one of my favourite southern galaxies.
I don't see much halo around the stars though. Which ones are you referring to? Star halos are a bit of a problem with astro processing - I agree. Its something I have had trouble with.
If its not hardware connected (poor quality glass in the corrector lens etc) and you are using good filters then I would look to 2 possibilities. One is the well depth of the sensor. The 8300 well depth is not that great so getting the right exposure length so the wells are not full and overflowing and the outer rings of the star don't expose too much. I found star blooming/halos most prominent with a 694 sensor which had relatively small wells. Overstretching the stars will do it too - usually in the RGB images. Blue often is the least sharp.
Greg.
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Cheers Greg- Exposure length appears to be largely guesswork for me in my recent forays into LRGB imaging.
I remember Ray (Shiraz) posted a conplex formula to define exposure times a while back but it went way over my head.
I’ll trial shorter exposures next time, with my 8300 chip- but I don’t want to be caught out mucking about under precious dark sky time for too long!
I wonder if folks here just do a ddp stretch or a more considered process of levels & curves prestretching when processing?
Quote:
Originally Posted by RickS
Nice one, Andy! There's no substitute for heaps of data on dim galaxies
Looks like you have a little misregistration between the channels? I don't know of any magic incantation that will give you perfect stars. It's a matter of getting everything you can right at capture and data prep time and then hiding any remaining warts later in processing
As Greg said, halos are pretty common. Careful focus and control of dynamic range will help but it's harder to deal with causes related to the optics.
Cheers,
Rick.
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Thanks Rick!
I’m attempting to eliminate variables one by one- hoping it’s not a hardware issue. But seeing Steven Mohr’s wonderful Insight competition Galaxy winning image really does make me wonder what difference a Planewave vs GSO scope makes?
They’re both just comprised of mirrors, not glass - so surely it’s not like a Tak vs Skywatcher refractor optics thing?
I reckon there’s a consideration for different exposure times between R & G,B that’s contributing to the misregistration issue too?
Quote:
Originally Posted by willik
That looks good Andy.
Martin
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Cheets Martin- reckon it’s about as good as I can get with my current skills & gear- thanks for the feedback!
(Was getting worried- could here crickets chirping here!)