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Old 04-06-2019, 09:54 PM
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Atmos (Colin)
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Atmos is offline
Join Date: Aug 2011
Location: Melbourne
Posts: 6,632
I cannot help much with views on those particular filters but the emission line that is being mentioned is the NII (Nitrogen II). It's very closer to the Ha emission. 3nm filters separate the two but a 5nm Ha filter contains both.
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