Light pollution filters

[Enrico]

There is some light pollution observing from my back garden. Question is, are the "light pollution filters" you can buy any good? They are quite expensive, so before I shell out any serious money I'd like some kind of warm feeling that it is going to make a difference.....

Thanks in advance for any help.

[jgs001]

I have a pair, although I use them for imaging... I have the SW LPR filter, and it does work, but lets through some of the LP in my area. This is a cheap option. I also have the Astronomik CLS filter, and this is a much more effective LP removal filter, to the point it'll remove light spill from the house.

[Moonshane]

Personally I prefer to reduce the effects of light pollution with a little more magnification - it has the effect of making the sky darker.

This may cost you nothing but I'd sooner have another eyepiece of higher magnification than a LP filter anyday.

yes, though, they do work to some extent (assuming the lights near you are of the right wavelengths (i.e. those covered by the filter you buy) but won't be a magic bullet.

[spaceboy]

LPR filters are designed to stop certain light wavelengths from entering the EP. As far as I am aware this is a wavelength that came from a certain type of streetlight (amber in colour) The usefulness of a filter depends on the street lighting you have installed around your observation site. It also depends on if you have a city, shopping center, car park etc, etc reasonably close. What I mean is you may have st lighting the filter will block with in 20 yards and do a good job but if there is a large car park 4 mile away sending light up in to the sky that has the wrong type st light then the positive effects of the LPR filter will be reduced. Filters do make an improvement IMO but how much is dependent on what the st lights are around your area. Sky watcher do a LPR filter for around £20 and they come up second hand fairly often so the best thing to do is give one a go. You might be lucky and find the lights around your way work with the filter.

Hope this helps

SPACEBOY

[spacebloke]

I heard good reports about the Baader IR-cut moon and skyglow filter, so I bought one, but because of the clouds I haven't had chance to use it :-(

[spaceboy]

I heard good reports about the Baader IR-cut moon and skyglow filter, so I bought one, but because of the clouds I haven't had chance to use it :-(

From what I have read on the internet it suggests Baader filters are more "filtered" than other makes. Which may offer better performance depending on personal preferences but could pose a problem in smaller aperture telescopes.

[michael.h.f.wilkinson]

I agree with spaceboy that it all depends on the type of LP. I just got a fairly cheap APM 2" UHC filter, and it does help quite a lot. However, it does depend on the object as well. Because an emission nebula only emits light which passes through the filter, they are much less affected by the filter than continuum emission from stars (and therefore elliptical galaxies) or reflection nebulae.

[Enrico]

Thanks for the replies. I'll put it on the wish-list and look out for bargains....

Now, if only there were some clear nights to get bothered by a little light pollution!

[Glowingsplint]

the Baader IR-cut moon and skyglow filter is the one a have because of the clear skys we have in our area i havent noticed much of a difference.

[umadog]

LP filters can make a lot of difference. Even from a dark site they can help. For some objects it can make the difference between visibility and invisibility. The UHC and OIII filters are particularly well thought of.

What you need to know, however, is that filters work best with magnifications of around 5x to 10x per inch of aperture. The reason is that they cut out quite a lot of light so they make the object you're looking at dimmer. So with a 5" scope you won't be able to go much about 50x with a filter in place. You need to think about that in the context of which objects you would like you view. Small planetaries, for instance, may become off-limits.

Due to dimming, it is particularly important that you dark adapt well (especially with a small scope) for filter use. If you have direct sources of light pollution which prevent you from doing that, then you may be disappointed by the filter.

[michael.h.f.wilkinson]

Last Friday I used my APM UHC filter on my 80mm, with 22mm EP for wide-filed viewing. Without the UHC filter I could not spot the Owl Nebula (M97), with it it was easy and I could see detail. For 65 euro for the 2" version, that is a very useful peace of kit!

[jumpclone]

sky in birmingham is usually glowing pink or white...think i need to get the hammer out and take care of those massive Street lights out side my blumming house

[chard]

I have a Baader neodymium LP filter coming over the next day or so.

I'll let you know how it fares. With London street lighting, at least.

[Carbon Brush]

If you look at the Baader & Astronomik web sites, there are wavelength/transmission graphs for the filters. Along with wavelength markers for various pollution sources & objects of interest. Very useful stuff.