Light Pollution Filters - Recommendations

[johnrt]

The problem of the LED's is they may be directing more of the light downwards, but you are pointing a scope upwards. That downward going light therefore still ends up in the scope.

Think the problem is that we use the term "light pollution" and maybe it is wrong, or it is too general and not specific enough.

Used to be meant that if you were 10 miles away there was a yellow glow over whatever town.

That however is when you are outside of the place looking at or towards it.

In many instances here we are sat inside looking out, not sat outside looking in.

Our concern in that situation is the ambient light.

Agreed, a street light / security light in direct line of sight to your OTA is much more devastating than the general sky glow. Just getting yourself shielded form nearby lights can make a big difference.

I will disagree with the post from above which said the effect of LP filters is overstated, I was able to triple my Luminance exposure time with the addition of the IDAS P2 filter (up to 15 mins now, and not over 5 before) it marked a stark improvement in my images and I leave it in place all the time even when shooting narrowband Ha & OIII with 3nm filters with no discernable loss of signal.

[glowingturnip]

Yes they knock out some sodium lines, but they also take a chunk of  light away from the object itself, and I have seen some filters where the second effect outweighs the improvement given by the first!

agree - I have one (can't remember the make) that I'd used a few times but wsn't particularly happy with, then figured out one day that it ws actually removing pretty much all of my red channel - haven't used it since.

[Toxophilus]

Thanks for all the suggestions. I have quite a lot to mull over.

[lensman57]

I'm in a really badly light polluted area, often the only way of seeing something is to try and image it with a 30 or more second exposure and actually viewing it directly is almost impossible at the moment hopefully things will improve in the winter. However when I do try to do an image, I often end up with the image being a lovely grey and a faint outline of the target buried in there somewhere, which I have to stack a few images and then manipulate to cut out the LP and pull the object out. This gives me some OK images  but nothing fantastic. Are there any LP filters that anyone can recommend. I have used the skywatcher one and that helps a little but it just does not seem to be aggressive enough. Unless of course there is some other technique that anyone can suggest for dealing with LP.

Thanks for your help/suggestions

Mark

Your best bets are the IDAS LPS, Astronomik CLS CCD  or the Baader UHC-s L Booster. These are all IR blocked and quite pricy particularly the IDAS. No LP filter will be able to filter out all the LP in the sky and they all have their own foot prints so depending on your target and your sky a lot of processing need to be applied but these will filter out the yellow orange glow of the sky if however, your LP is caused by the new menace of the LED street lighting then I am afraid that the game is up as these filters will be next to useless in dealing with the white light pollution.

A.G