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Old 10-08-2020, 09:09 AM
Granada
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Light pollution filter

Wondering does a light pollution filter (e.g., Astronomik CLS EOS APS-C) need to be used in conjunction with other filters (e.g., clip on the CLS filter to the DSLR, then add Ha/Sii/Oiii to the filter wheel) or by itself?
I guess what I'm not understanding is, since the light pollution filter filters out light pollution to make it seem like a dark site, do you then need to put other filters on top of it to filter out further bands (just as you would at a dark site), or how does it work?
Cheers!
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Old 10-08-2020, 01:35 PM
RyanJones
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Hi Granada,

A CLS filter essentially only cuts out the region of light associated with the wavelengths on light emitted by artificial light sources eg. Street lights. On the other hand your O3 Ha and S2 filters only let though the specific wavelengths of light associated with the respective gasses. Hence, if you are shooting using a specific band filter, there should essentially be nothing left for the CLS to cut out that it is designed to do if that makes sense ? The band specific filter has already cut it out.

I hope this clears things up


Cheers
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Old 10-08-2020, 01:42 PM
Granada
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Quote:
Originally Posted by RyanJones View Post
Hi Granada,

A CLS filter essentially only cuts out the region of light associated with the wavelengths on light emitted by artificial light sources eg. Street lights. On the other hand your O3 Ha and S2 filters only let though the specific wavelengths of light associated with the respective gasses. Hence, if you are shooting using a specific band filter, there should essentially be nothing left for the CLS to cut out that it is designed to do if that makes sense ? The band specific filter has already cut it out.

I hope this clears things up


Cheers

Yep that makes perfect sense - thank you.


I guess that begs the question then - if you're planning on purchasing/utilising those other filters, is there any point in purchasing a CLS filter as well? Would you only use it in situations where no other filters are needed, but there is just too much light pollution in the way (i.e. planetary, star trails, etc.)?
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Old 10-08-2020, 02:23 PM
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roberto84 (Robert)
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Slightly off topic question sorry, are light pollution filters mainly a benefit to astrophotography or do they benefit naked eye observations? (noticeable difference).

I am just outside Brisbane in what would be an orange/dark orange light pollution site.
https://darksitefinder.com/map/
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Old 10-08-2020, 02:28 PM
Granada
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Quote:
Originally Posted by roberto84 View Post
Slightly off topic question sorry, are light pollution filters mainly a benefit to astrophotography or do they benefit naked eye observations? (noticeable difference).

I am just outside Brisbane in what would be an orange/dark orange light pollution site.
https://darksitefinder.com/map/

My understanding is that you can use them for both visual and astrophotography purposes, but having never used one previously I can't say how much of a difference they make to visual observing. Would be keen to hear from others because I too live in a very light polluted area.
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Old 10-08-2020, 03:17 PM
RyanJones
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Yes and no. When you image in narrow band it affects star colour. Often seperate images are taken unfiltered to layer RGB stars into a narrow band image. The CLS maybe useful in this situation to reduce the sky glow in that layer.

The alternative, if you are using a DSLR or a OSC camera is to buy either a dual, triple or quad band filter. Although not cheap they are a stepping stone into narrow band as they have several narrow bands in one filter. The STC duo I use is an example of this and it is amazing at blocking light pollution.
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