use of light pollution filters with LRGB mono imaging

[javajunkie2121]

Hi All:

I'm moving from one shot color CCD to a mono CCD with filters to do LRGB imaging..I live in a light polluted area.

Do folks living in urban settings with light pollution use a light pollution filter with LRGB imaging? 

If so, is the LP filter in front of all filters?
Supposedly the Baader filters I am getting have a gap between red and green to account for streetlights, but Kayron Mercieca has posted information on his site that it still isn't enough to eliminate light pollution from the red channel.

Or, do you all substitute the light pollution filter for the luminance filter?

jeff

[pfile]

when i moved from a DSLR to LRGB mono, cooled CCD i was amazed at how much signal i could get even here in this red zone.

i think that the RGB filters all have way too wide bandwidths to really avoid LP the way narrowband filters do. having said that, the RGB filters i own also have gaps between them that are supposed to cut out some of the major sources of light pollution. but with so much more outdoor lighting moving to white LEDs, we might be doomed. those lights are really broad-spectrum, as opposed to the sodium vapor lights that used to be popular.

if i shoot into a direction with more LP i usually just forgo the L filter and make a "super L" out of the RGB images. either way careful DBE and ridiculous integration times are always necessary when i image from home.

so in answer to your question, you will probably be able to get by without a dedicated LP filter. it's worth trying without it first, at any rate.

rob

[MikeOates]

Jeff,

As Rob says, I was also very surprised at the amount of signal I can get for my light polluted sky in Manchester UK. I use Astrodon E-Series filters and if you loo at the spectra [http://www.astrodon.com/custom/_2e2a/content/images/AstrodonG2ESeriesScansforWeb.jpg] you will see a gap between the green and red, this means most of the light pollution is filtered out.

But, this does mean that the Lum filter can't be used as that includes the light pollution, so I do as Rob says and just image as RGB at 1x1 binning. Before I tried them I was thinking I would also need to fit another LP filter in the light path, but I am now glad I don't need to. I can do 10min exposures with my RGB filters which is fantastic.

My sky brightness is typically around SQM 18.5

Mike