Old 23-03-2013, 02:28 PM
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White Rabbit
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LRGB imaging and light pollution.

I'm about to delve into LRGB imaging and have a question about light pollution.

I have and use a Astronomik cls ccd light pollution filter on my 5D MKII. It works really well and enable me to stretch my subs out 6 or 7 mins in my very light polluted sky's.

Question: do I still use my CLS filter with the LRGB filters?
I would imagine I would still use the filter?

I'm yet to start my research on LRGB imaging, can you recommend some good resources?

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Old 23-03-2013, 06:18 PM
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Colour is over-rated

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I've never tried it - but apparently you can use it for the L frames....

From the bintel website:

it suggests using it for luminance frames in the info below......
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Old 24-03-2013, 03:53 AM
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PRejto (Peter)
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I have used my Hutech IDAS LP filter with L and RGB filters (Astronimik). I came to the conclusion that I should use the LP filter by looking at the transmission curve of the Hutech and comparing it to the RGB Astronomik filters. It was clear that the IDAS was blocking certain frequencies that would have been allowed to pass if I used just the RGB filters alone.

I think there are some filters (Astrondon?) that claim to inhibit light pollution in RGB so possibly with certain RGB filters it might not be necessary to use the LP filter. And then this could be refined if one specifically knew the type of light pollution one wanted to block. In any case I have had some pretty decent results using the LP filter with LRGB though the exposure increase rather a lot!

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Old 24-03-2013, 04:09 AM
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Tandum (Robin)
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Peter's right, you need to overlay the cls response curve with the curve from your filter set.

This curve is from the filters that come from QHY. I asked why there is a gap and was told it was to stop light pollution.

I don't use any LP filters here.
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Old 26-03-2013, 10:21 PM
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White Rabbit
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Thanks for the info. I've been doing a bit of research on the subject and everything seems to concur with the above.

It's really quite amazing to think that as a species we have bee n able to figure all this stuff out. Fascinating.

Thanks again.
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