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Old 02-09-2013, 10:29 AM
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PRejto (Peter)
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Join Date: Jan 2011
Location: Rylstone, NSW, Australia
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Hello Ray,

Thanks for the S/N formula and your comments.

The more I ponder this the more I think that I should continue experimenting. Perhaps the conditions that I tested the two filters was too severe as I would never try to actually image so low towards the horizon. And, yes, I do think that the large frequency of light blocked by the CLS could prove to be a problem for some targets, particularly those containing a lot of blue. The frequencies cut by the CLS are quite broad as can be seen in a comparison of the spectrum graphs.

I'm not sure I have done the Hutech IDAS filter any favour in the first photo attached in my first post as I just let CCDStack stretch each in an automatic fashion. I suppose that isn't entirely fair. So I also attach below the unstretched raw frames as displayed in Photoshop.

Next clear night I will repeat this experiment but close to the meridian where I more typically image. There is much less LP and I expect that I might see a better result from the Hutech IDAS filter. At least I hope so because I'm not sure I want to pay the price for very long exposures in luminance using the CLS vs the IDAS, nor do I want to miss collecting faint blue stuff. Looking at the transmission in blue of Astrodon filters frequencies from about 380 nm up are transmitted. The IDAS will capture some of those and the CLS will not.

Peter
Attached Thumbnails
Click for full-size image (CLS+IDAS-02 raw frames.jpg)
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Click for full-size image (CLS & IDAS Frequency Spectrums.jpg)
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Last edited by PRejto; 02-09-2013 at 11:11 AM.
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