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Old 24-04-2013, 02:21 PM
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White Rabbit
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Ha fillters?

Hi guys.

I'm looking at getting a Ha filter but see that they come in a few different wavelengths.
To start off with what would be the best to get. I'm assuming the the 12nm would be the most versatile as it seems to be most readily available?
Can you explain the different application for the different wavelengths are.

Thanks
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Old 24-04-2013, 02:38 PM
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pluto (Hugh)
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I bought my narrowband filters primarily so that I could image from light polluted Sydney and take advantage of clear nights even when the moon is up. My understanding is, for this purpose, the lower the bandwidth the less light pollution will affect the image but exposures will have to be longer as less light is getting through.
I ended up getting the Baader 7nm Ha as it was a good compromise on bandwidth and price.
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Old 24-04-2013, 02:39 PM
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jjjnettie (Jeanette)
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Plenty of good info here. Plus else where on the Net. http://www.youtube.com/watch?v=E842Rs-iB2I
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Old 24-04-2013, 04:19 PM
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Merlin66 (Ken)
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Ha emissions are only 0.3nm bandwidth..
All the Ha filters do is allow more (or less) background light to get through. With a very narrow bandwidth filter <6nm you can have issues with very fast f ratios.
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Old 24-04-2013, 05:38 PM
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Bassnut (Fred)
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What Ken said and imaging over f3 with the SBIG in Sydney it's well worth stumping up for an Ha 3nm. The rest of th NB filter set can be wider, the detail is in Ha.
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