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Astronomik CLS-CCD vs. Astronomik CLS filters

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#1 end

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Posted 20 February 2013 - 02:59 PM

I have a Canon 60Da and recently acquired an Astronomik EOS clip-in filter for H-alpha which I love. Building on this I'd like to add a light pollution filter and I'm confused on which of the following I should get: the CLS-CCD or the plain CLS filter.

From the Astronomik web page:

Technical Data CLS-CCD

• 95% transmission at 486nm (H-beta)
• 95% transmission at 496nm (OIII)
• 95% transmission at 501nm (OIII)
• 97% transmission at 656nm (H-alpha)
• pass from 450 to 520nm and from 640 to 690nm

Technical Data CLS

• 92% transmission at 486nm (H-beta)
• 92% transmission at 496nm (OIII)
• 92% transmission at 501nm (OIII)
• 97% transmission at 656nm (H alpha)
• pass from 450 to 540nm and beyond 650nm

My understanding is that the major difference between these two is that the CCD version adds a filter to block IR beyond 690nm (ie: does not block H-alpha). Given that the 60Da is not a full spectrum detector like most CCDs are and yet has an extended detection window, it isn't obvious to me which is going to give me better performance. The transmission percentages for the CLS-CCD are somewhat better than the CLS, but since Astronomik does not publish their entire transmission spectrum (does anyone have this, by the way?) it might be that the CCD version is more transparent across the board and this isn't a real advantage.

Can anyone help me make this decision? The CLS-CCD is somewhat more expensive, but the difference in price does not concern me.

Thanks!

#2 piaras

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Posted 20 February 2013 - 04:23 PM

The transmission charts are on their site. At the top click on Datasheets.
Pierre

#3 end

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Posted 20 February 2013 - 08:33 PM

The transmission charts are on their site. At the top click on Datasheets.
Pierre


Thanks! I don't know how I missed that before, I thought I had looked all over for them, but I guess not.

It looks to me like there isn't a huge difference between these but possibly the CCD one would be slightly better over all.

Does anyone else have thoughts on this?

#4 wolfman_4_ever

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Posted 20 February 2013 - 10:52 PM

cls-ccd i use for still's,

cls i use for video... don't do visual..

#5 Tom and Beth

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Posted 21 February 2013 - 12:04 AM

When I researched this last month, the CLS was for an unmodded DSLR. Since your 60Da is sensitive in Ha, you want the CLS-CCD. At least, that was my takeaway. I bought the CLS for my stock XSi.

#6 piaras

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Posted 21 February 2013 - 04:34 PM

I bought the CCD version as I have a modded 350d and a T3i that is not. I can use it on either one but naturally it is used on the 350.
Pierre

#7 calypsob

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Posted 25 July 2013 - 11:05 AM

Cls ccd blocks ir and uv light. A ccd or clear glass modded dslr cannot block uv or ir so a refractor can have bloated stars as they are usually not designed to focus these frequencies of light. A mirror lens newtownian will not have problems with star bloat so the cls would be fine for mirrors. I have a clear glass 550d and the cls ccd supresses ir and uv very well. I have never seen anyone try to image ir or uv before but if you had a cls clip filter on a full spectrum dslr then i suppose you coul use a 48mm ir pass filter or uv bandpass to image those specific frequency ranges with a newtonian.

#8 rainycityastro

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Posted 25 July 2013 - 11:12 PM

A mirror lens newtownian will not have problems with star bloat so the cls would be fine for mirrors.


Not quite true. CCD chips dont perform really that well into the deep infra red unless they are explicitly designed to do so.
Don Goldman's analysis

Your best bet is to always get the filters that attenuate the UV/IR range of the spectrum if you are imaging.






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