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Old 15-11-2008, 12:05 AM
Craig_L
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Narrow Band Imaging with H Beta

Just wondering whether anyone is doing narrow band imaging with OIII, H Alpha and H Beta filters (H beta instead of a SII filter)? What narrowband filters do you need to simulate the RGB palette of colours rather than the Hubble pallette? I was thinking H Beta - blue, OIII - green, H Alpha - red.
Any thoughts appreciated.
Craig
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Old 16-11-2008, 10:06 PM
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Tandum (Robin)
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Sorry craig, I got some filters but it's been overcast and stormy up here since October
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Old 16-11-2008, 11:22 PM
Craig_L
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Hi Robin,

Been cloudy here for the last couple of weeks as well.

What filters and what brand do you have?

Craig
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Old 16-11-2008, 11:27 PM
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Merlin66 (Ken)
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H beta emission is so close to the OIII emission that depending on the bandwidth of the filters being used, you may find little or no difference between these two images.
Added:
An easy way to check is to fit one of them, look at the image and then add ( ie double them up) the other filter; if the initial image disappears then the cut-off of the second filter is OK

Last edited by Merlin66; 16-11-2008 at 11:29 PM. Reason: explaination
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Old 17-11-2008, 08:24 AM
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I have been doing 'natural' narrow band imaging for a while using HA and O3 filters. I assign the HA to RED. The O3 actually falls between the Bayer filters on a DSLR and exposes the blue and green pixels about equally. If you then assign the green to Green and blue to Blue you will produce the cyan colour of O3.

When monatomic Hydrogen atoms are stimulated by nearby stars they emit HA and Hb. The intensity of the Hb is about 0.30 of that of the HA. What we see on Earth is a different matter as the blue Hb is attenuated more than HA by any intervening interstellar dust and extinction in the Earths atmosphere. You can always produce a Hb signal by doing pixel maths on a HA image. That is multiply by 0.30 or less if you want to simulate extinction.

The next thing to do is to collect colour data to get the correct star colours.

Here are a couple of examples.

Just HA and O3.
http://www.iceinspace.com.au/forum/s...ad.php?t=37660

These are with HA O3 and colour and HDR to preserve dynamic range.

http://members.optusnet.com.au/~fmlee/lmchdr_col+nb.jpg

http://members.optusnet.com.au/~trlee8/col+ha+o3.jpg


I do have a Hutech filter that records all blue from Hb up. This is most useful in separating blue from O3 from that of blue due to Hb and blue reflection nebula.

I use ImagesPlus for combining the different colour images. It is essential that they have the same size and content for combination and I use RegiStar for this.

Bert

Last edited by avandonk; 18-11-2008 at 08:30 PM.
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Old 18-11-2008, 12:47 PM
Craig_L
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Thanks Merlin and Bert. I started doing the sums for all this and it's going to be expensive if I get the filters and a filter wheel for the Tak Sky 90 and its adaptors. I guess I'm wondering whether the narrowband filters will cut through my polluted skies a lot more than the Hutech LPS-V3 filter I have at the moment. Thanks also Bert for confirming I need something like RegiStar to get process the different images to get the same size as I can't just align and stack them in a program like Nebulousity. More pondering required I guess.

Craig
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Old 18-11-2008, 07:57 PM
Mighty_oz (Marcus)
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Nice pics there, tried following your first link Bert, ngc2070 i think, not found
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