LRGB imaging quick question.

[GrantEb]

Hi all

Was just wondering something, out of interest really.

When you guys do LRGB imaging with a mono CCD, do you use a light pollution filter? (In conjuction with a colour filter, and on your L channel run)

Hopefully you understand my question.

Thanks

Cheers

[antimorris]

I have never used a light pollution filter when imaging, though I believe that some people do (don't quote me on that though) ... I guess it might depend on where you are imaging from though even in a heavy light polluted city in the US (San Antonio) I never used one.

[MikeD]

I have had a CLS filter for years and did try it when I first got it but found it made getting the RGB colour right very hard.

It seemed to kill the red response.

All the LRGB images I have taken so far (see my website) have been without a dedicated LP filter.

To help with the LP I have found shooting Ha data and mixing it with the red data is a very good way of filtering the LP out and at the same time increasing the Ha in galaxy images.

I say up to now as I have just this week reintroduced the CLS filter into my imaging train.

My setup is now..... CCD-CLS(1.25")-filter wheel(L-R-G-B-Ha)-OFF axis guider-MPCC.

I have only so far shot L data with the new setup, it has helped me to image under conditions I would have even bothered without the CLS filter. Here

The big test is when I shoot some RGB data although I do plan to significantly increase the exposure time for the red data this time.

Mike.

[GrantEb]

Thank you very much for the informative responses. Does get my head around it a bit.

So, I have seen, when doing your L exposures, you expose for 10 mins +, how do you do that without "over exposing", or having LP "wash it out"?

Thanks again

[MikeD]

I only expose L for 5 min's without an LP fliter, any of my mono images longer that 5 min's have been taken through a Ha filter.

Mike.

[GrantEb]

Ok, I get it now.

Thanks Mike.

[ollypenrice]

My LP filter is the 110 Km that separate me from the nearest major town and a series of mountain ranges that act like light baffles for more local villages! Works a treat!!!

More seriously, a number of guests who have reasonable sites at home say that they sometimes do the Lum at home and very often the Ha (not surpizingly) but that the dark site really matters for the RGB.

Olly

[GrantEb]

I have to get one of those LP filters!!!

I will be in New Zealand soon, so hopefully will be better.

Thanks Olly.

[martin_h]

I use an LP filter in my LRGB setup, but from the Baader site they state -

"Gap between G/R-filters serves to reduce light pollution from Mercury and Sodium lamps and improves colour balance and separation"

[GrantEb]

Thanks Martin, that's very interesting.

[Catanonia]

Nope never use one, I can happily image at 10mins without problems, before CCD it would have been 2 mins.

The filters work well at giving you what you need, well mine do, QHY9 filters.