CLS LP filter with LRGB imaging...

[Astroboffin]

Hi all and a happy new year

This question has bound to have been asked before so apologies for that.

When doing mono imaging, and suffering from moderate to high LP, should I use my CLS LP filter with each of the LRGB filters when imaging to combat the LP, or will the RGB filters themselves not let it through, (for want of better terminology)

I realise I should probably use it with the L filter, or should I......??

If so I am thinking of having it mounted in front of the filter wheel so it is there all the time and free up a slot...good or bad idea.

AB

[Astroboffin]

Well no advice, maybe everybody still hungover.......lol

AB

[Astroboffin]

Wow, maybe the question was more stupid than I thought......

AB

[Astroboffin]

Ok, I have found the answer, been reading old posts and found loads of info

AB

[RikM]

Sorry, didn't see your post until now. There is no 'best' answer to this one. Personally, I leave my light pollution filter in place for all other filters. I ran a short with/without trial and for my set up and my light pollution, it was better with the filter in place even for the RGB filters. It didn't seem to hurt the narrow band filters either, so for ease (read laziness) I just leave it in place and don't touch it.

[Astroboffin]

Hi,

Thanks for that,

Yes that is what image read, but by leaving it in place, will that make it harder to achieve focus through it, or because the CCD is so much more sensitive than my DSLR will it be ok, also it means I will be imaging through two filters all the time, so I would have to get focus through two filters, but how would I do this, if I have got Ha, RGB, in the filter wheel and CLS (for luminance) on front of wheel..? I would have to focus through one of those four filters plus the CLS, is that a good idea ?

AB

[RikM]

If the filters are of good quality, you shouldn't have any issues with focus. With stacking filters there is the chance of internal reflections causing halo artefacts etc., but I haven't had any problems like that myself. (Doesn't mean it couldn't happen though). I actually put my light pollution filter on the front (focuser end) of my coma corrector, so it's in place if I am using either of my DSLRs or my CCD. I don't use the filter wheel with the DSLRs though. (Filter removed 350D and unmodified 1000D)

As I said, there is no 'best' answer. I have seen outstanding images from people who stack filters (as I do) and from folk who replace only the L filter with the CLS so the other filters are used individually.

It may well be sky condition dependent. My sky is pretty crummy, and it doesn't seem to make much difference to my images if I stack the filters or not. Therefore I stack them for convenience. The best images from people who don't stack filters, seem to come from darker locations, so it could be that under those sky conditions, or with more expensive kit you can see a difference. Theoretically of course, the fewer glass elements the light passes through the better, because each one will cut the light by tiny bit. In my case, without the LPR filter the RGB was slightly less contrasty and looked 'muddy' somehow.

[Astroboffin]

If the filters are of good quality, you shouldn't have any issues with focus. With stacking filters there is the chance of internal reflections causing halo artefacts etc., but I haven't had any problems like that myself. (Doesn't mean it couldn't happen though). I actually put my light pollution filter on the front (focuser end) of my coma corrector, so it's in place if I am using either of my DSLRs or my CCD. I don't use the filter wheel with the DSLRs though. (Filter removed 350D and unmodified 1000D)

As I said, there is no 'best' answer. I have seen outstanding images from people who stack filters (as I do) and from folk who replace only the L filter with the CLS so the other filters are used individually.

It may well be sky condition dependent. My sky is pretty crummy, and it doesn't seem to make much difference to my images if I stack the filters or not. Therefore I stack them for convenience. The best images from people who don't stack filters, seem to come from darker locations, so it could be that under those sky conditions, or with more expensive kit you can see a difference. Theoretically of course, the fewer glass elements the light passes through the better, because each one will cut the light by tiny bit. In my case, without the LPR filter the RGB was slightly less contrasty and looked 'muddy' somehow.

Thanks very much for that, I think I have made my mind up now, as my LP is above moderate, so am going to leave the CLS on all the time and also leave the L filter in the wheel, so that when I focus I can do it through the L filter and CLS, so still going through two filters, so should be parfocal when imaging through either RGB and the CLS....hope that makes sense

AB