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Old 30-11-2010, 10:09 PM
Hans Tucker (Hans)
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Combining Ha Filters

Is there any benefit, advantage or the like imaging through a 6nm & 12nm Ha Filter and combining the results...would it produce a better defined image compared to just imaging alone through a 6nm or 12nm. Or does this idea just display a poor understanding of how these filters work.
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Old 02-12-2010, 12:25 PM
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Moon (James)
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I think you would be better off spending the time using 2 totally different filters like Ha + OII or SII. It would give you more information about the object you are imaging.
However if you have both the 6nm & 12nm filters already, then it wouldn't hurt to do a test sometime to see if you can detected any difference in performance, especially if you have a very fast scope. Also checking for reflections etc and see which one you like best.

James
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Old 10-12-2010, 12:58 PM
jase (Jason)
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A lower bandpass results in a darker background ADU count so has the ability to pick out the fainter signal of the emission line. This would probably be lost when trying to combine the data. You could get tricky and use pixel math to favour certain characteristics of an image, but I doubt the result would be worth it.

A lower bandpass is more effective at cutting through light pollution if imaging from the suburbs, but in reality a moderate bandpass is as good. Obviously this also assists in increasing the time before you hit the sky glow limit. Many opt for 3nm SII and OIII filters to maximise the signal from these emission lines. Anyone who's done narrowband imaging will note that getting good SII data can be a challenge. HA on the other hand is much easier to pick out and get good signal on. Would suggest getting a moderate to low bandpass but be prepared for long exposure times.

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