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Old 22-03-2012, 07:55 PM
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troypiggo (Troy)
Bust Duster

troypiggo is offline
Join Date: Nov 2008
Location: Brisbane, Australia
Posts: 4,833
5nm vs 3nm narrowband filters

I'm in the process of swapping my Astronomik NB filters over to Astrodons. I recently posted here about halos/reflections in the Astronomiks. I've sent them test shots, and await their replacement filters so the problem will go away. But they're 13nm bandwidth.

But that being said, I always intended to go narrower bandwidth on the NB filters. Been doing some reading on the 5nm vs 3nm recommendations:

Ha: the 3nm filter cuts out the NII bandwidths as well, while the 5nm does overlap a little so you do gain some NII signal in some planetary nebula etc. Since I don't want to get a special NII filter, I'm thinking of going with the 5nm for Ha

OIII: I understand that OIII is more susceptible to moonlight. So the 3nm is recommended over the 5nm for this reason? But are there cons to doing this versus keeping it 5nm to match the Ha? I'm leaning towards the 5nm for cost and matching reasons.

SII: Not much I could find on this, so thinking 5nm to match the Ha as well.

So my dilemma is more about the OIII, and whether to get the 3 or 5. Any issues or comments to add?

I can't justify getting 3nm for all filters.
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