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Are light pollution filters really effective?


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I have quite a problem with light pollution where I live and am thinking that a LP filter would be a good idea for visual observing.

However are they really effective? Although they should cut out the light glow from the street lamps, shops, and a retail park, will they also reduce the light gathering ability of the scope and therefore 'dim' the view and in practical terms not gain a lot.

I would be interested to hear other peoples experiences and what situations were addressed and whether their observing was improved by much. And if there was a major improvement which filter were you using?

Thanks

Nick

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I also suffer from light pollution but I have the Baader Neodydium filter and I find it helped me observe those faint little galaxies in Virgo and Coma Berenices.

But then I have 16" of aperture, so thats alot of light in the first place.

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Hi!

IMHO filters are useful only on nebulas, since most of them produce light with a "line-spectrum" (lines of O-III, H-beta).

With line-filters or narrow-band-filters you can improve the contrast several times cutting everything except theese emission lines.

For example with my baader O-III filter (8.5nm bandwidth) I've seen the veil nebula with the 35cm of a friend of mine, from suburban sky (I live near Milan, one of the worst skies of Europe)-

UHC filters do a good job, they are less selective but still they improve contrast very well.

Broad band filters (LPR, UHC-S, UHC-E) are useful only if the street-lamps neay you have a line spectrum as low-pressure sodium lamp (Sodium-vapor lamp - Wikipedia, the free encyclopedia).

The real problem of nebular filter is that each of them works well with a particular exit pupil: eg: O-III filters need a lot of light, so you cannot use them on small telescope at high power, UHC filters need less light etc.etc...

With your 8" I suggest you a good UHC filter (not baader UHC-S nor astronomik UHC-E). Very good are Thousand Oaks LP-2, Meade narrowband or Orion Ultrablock. There are cheap UHC filters on the market, like Omegon UHC, but I don't know them (sincerely I would like to test them since they are very cheap).

Here you can find a very useful article with perfomance of different kind of filters on different deep sky object: Filter Performance Comparisons - Article

ciao

dan

Edited by weega
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I would say that the Neodymium filter is only any good against the old style yellow sodium lighting. If it's anything else I would suggest paying that bit more and getting one of the more expensive ones.

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They are effective, well better then nothing, if you have sodium lights.

If you have problems from halogen lights then somewhat less so as you cannot remove all the unwanted wavelengths.

Sodium lights were "good" in that they were a couple of spectral lines and filtering them out was relatively easy.

The new lights being installed are "white" so filters will be limited in what they can do, if anything. And as they are fitted with hoods more of the light is going downwards so we could be sat inside a brighter environment.:eek::icon_scratch:

So it comes down to the nature of your light pollution.

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