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Baader v CLS

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#1 StarBurger

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Posted 18 February 2019 - 06:18 PM

I am still agonizing about whether I bought the best LP filter for AP using my modded Canon XS.
Local LP sodium lights are my bug bear .
I bought the Baader Moon/skyglow Neodymium on recommendations and after extensive research.
Now I learn that the CLS filter may have been a better choice. I have seen that many reviewers are calling the Baader a "mild' filter and the CLS a "medium", and the narrow bands a "strong", of course.
As far as I can determine, looking at the transmission curves, both are very similar. They both cut out the low pressure sodium  between 550 and 600 nm which is where all of my LP is.
The only major difference is that the Baader passes around 50 % at 530 nm while the CLS does not. I do not see any line at this wavelength included in LP that I should worry about. Hg at 546 nm is mostly passed but Hg is not part of my local LP.
So-what really determines what is a mild versus a medium LP filter? Does the Hg pass make the Baader a mild? Also I note that another Hg line at 435 nm is a borderline cut with the CLS but total cut with the Baader.
Is this a case of six of one and half a dozen of the other?
The proof will come when I am able to collapse the wave function of photons under a clear and warm sky, whenever that may be....

What's the skinny here?


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#2 bridgman

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Posted 18 February 2019 - 08:03 PM

You'll probably get a lot of different answers here, but my impression is that you'll have best results with the mildest filter that targets your light pollution sources, since the more aggressive filters have more impact on colour balance as well.

 

One school of thought says "use the more aggressive filters; it's easy to correct the colour balance" while the other says "use the less aggressive filters; it's hard to correct the colour balance", so part of the answer seems to involve getting some experience with correcting colour balance before spending too much on aggressive filters.

 

I'm just getting back into this after ~15 years away - before most of the neat new LP filters were developed - so learning as well. What I can say with at least a bit of confidence is that if your LP is primarily from low pressure sodium then a wider range of LP filters will work for you... once you get into LED and high pressure sodium it gets a lot harder to reduce LP without also filtering out light you want to capture.

 

BTW unless your modded camera includes an IR cut filter you probably should be looking at CLS-CCD instead of the regular CLS filter if you decide to go that way.



#3 StarBurger

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Posted 18 February 2019 - 10:48 PM

Thanks bridgman. Nice to have some confirmation I am on the right track.

That Baader neodymium filter has more UV cut (<400 nm) and an IR cut at > 700 nm .Since there ain't much IR light to collect above 700 nm I am happy to believe that the Baader is just  a UV/IR cut filter (which I have anyway) with the inclusion of a sodium cut  and that the full spectrum mod collects everything available.

So far I have never had issues with color balance. I LOVE cranking Star Tools color balance and anyway color IMHO is a matter of taste.




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