CCD and LP Filter?

[gnomus]

Another beginner question....

As soon as I combined the R, G and B channels on my first CCD image - http://stargazerslounge.com/topic/248909-first-attempt-with-new-ccd-pelican-nebula/ I noticed that I had a distinct orange colour cast.  I ran the RGB file through DBE and I think I got most of it extracted.  This is what DBE took out of my image:

I imagine that this must be light pollution.  Now, I took this image at a time of year when I am not getting any proper darkness where I live.  Furthermore, I was so eager to try out the new camera that I started capturing too early probably.  The first 5 minute capture was a near "grey-out" (if that's a term).  It may be that when I start getting proper darkness I won't get this colour cast (at least not to the same degree).  I would describe my locations as semi-rural.

When I was taking pictures with my modified DSLR, I did have an IDAS LP filter.  Do people combine their CCD L, R, G & B filters with a LP filter when capturing?  I can screw my filter into the filter-wheel nosepiece and so could construct the following chain:

Camera (Sensor) - LRGB filters - IDAS - telescope

If people do do this, do they use the LP filter with all of the L, R, G & B filters?

Thanks for your patience.

[swag72]

I don't use a LP filter for my RGB imaging...... but I do use one in place of the luminance filter. Its not parfocal with the other filters of course (not that anything I own is parfocal anyway!) but with auto focus that is not an issue at all.

[ronin]

Don't go imaging myself but I would have thought that the RGB filters would not have passed whatever wavelength the light pollution was, certainly not the sodium wavelengths.

Which RGB filters are you using?

[gnomus]

Don't go imaging myself but I would have thought that the RGB filters would not have passed whatever wavelength the light pollution was, certainly not the sodium wavelengths.

Which RGB filters are you using?

The Baader CCD filters.... As I said I could have been capturing some daylight!!

[Scott]

Don't go imaging myself but I would have thought that the RGB filters would not have passed whatever wavelength the light pollution was, certainly not the sodium wavelengths.

Which RGB filters are you using?

surely, if that was the case then dslr cameras would not be affected by light pollution? they are after all rggb. I may well be wrong though so I'd like a diffinitive anwser if anyone knows

[Mr Spock]

Don't go imaging myself but I would have thought that the RGB filters would not have passed whatever wavelength the light pollution was, certainly not the sodium wavelengths.

That's not the case. RGB filters have wide bands. Baader and Astrodon claim there is a gap between red and green of their RGB filters to remove sodium light pollution. Practice shows this is not the case and there is some overlap.

There is a need to use an LP filter on all LRGB filters to avoid LP

[johnrt]

I use an IDAS stacked in front of all my filters LRGB and even Ha & OIII too. It makes the world of difference (not to the narrowband I'm just too lazy to remove it).

[steppenwolf]

I use an IDAS stacked in front of all my filters LRGB

Me too!

and even Ha & OIII too

Noooooo!

[RikM]

I use a LP filter in front of LRGB filters as well.

[Spikey]

I use an LP filter with LRGB but not narrowband. I've noticed LP doesn't affect Ha that I've noticed, but will creep in on O3 & S2.

[Uranium235]

You shouldnt really rely on "one click wonders"  (ie: DBE) when it comes to sorting out your colour in LRGB. Any channel can be affected by higher background levels at the time of shooting (either by lack of proper darkness, high cloud etc).  Take time to align the channels properly using levels and the colour should sort itself out, there are no shortcuts when it comes to colour  balance.

Thats my 2p worth anyways.

[Tim]

I use an IDAS stacked in front of all my filters LRGB and even Ha & OIII too. It makes the world of difference (not to the narrowband I'm just too lazy to remove it).

Same here.