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Old 10-09-2014, 08:28 PM
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pluto (Hugh)
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OIII 8.5nm vs 3nm under full moon

Just got my Astrodon 3nm OIII filter today so I'm giving it a go tonight.
Just to see the difference under matching conditions I left the old 8.5nm OIII filter in the wheel and did a couple of images to compare.
I did a 30 minute exposure with each.

The first image shows both images with the same histogram stretch applied to both. The 3nm is on the right.

The second image shows both images with an auto screen stretch applied to both. Again the 3nm is on the right.

Interesting?


P.S. I know that 3nm image is out of focus, I've fixed that now
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Old 11-09-2014, 07:43 AM
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SamD (Sam)
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Yes Hugh, you ought to see a decent SNR improvement going from 8.5 to 3nm.

Annoyingly though, you lose the 495.9nm OIII line on the 3nm filter, but this is normally only about a third the strength of the main OIII line intensity.
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Old 11-09-2014, 03:35 PM
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pluto (Hugh)
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Yeah I'd read that before I went for the 3nm. I think it's a good trade off given the ridiculous light pollution where I do a lot of my NB imaging.

I've decided to go with 5nm Ha though instead of the 3nm so I can keep the NII light.
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Old 26-09-2014, 06:32 AM
antimorris (Anna)
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I am considering splurging to go from the 12nm to the 3nm despite the loss of the 495.9nm for this very reason. The difference, I imaging, would be even more pronounced with the larger spread of the 12nm that I have. It is nice to see the comparison, thanks for posting it!
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