M106, an experiment with LP filtering

[MikeD]

I have a Astronomik CLS filter I bought for my toucam pro II in 2004,and Have never used it when LRGB imaging, as Back then I found it killed the red signal and made colour balancing a nightmare.

I decided to dust it off and try again.

I managed to get the 1.25" filter in the imaging train between the CCD and filter wheel a few weeks ago.

Last night I pointed the scope at a mag 9 G2V star and set about working out what exposures I would need to use to bring the red back into line with the filter in place.

The results surprised me, to get around the same average pixel value on the core of the star I had to shoot:

B @ 10 secs

G @ 7.5 secs

R @ 40 secs

I worked out That Would be some thig around B @ 400 sec's, G @ 300 sec's and R @ 1600 sec's.

As the L data I had shot was only @ 600 sec's this just didn't seem right:confused:

So I settled for RGB = 900, 300 and 400.(still more for the red than the L but that's what my tests were telling me)

So to add to the 30 @ 600 sec's L data I had already shot i set a run of

R = 4 @ 900 sec's

G = 12 @ 300 sec's

B = 9 @ 400 sec's

A total of one hour per channel.

The result below has no Ha data just LRGB and the colour came very easily apart from still having to push the red to compensate for not going with the 1600 sec's my test told me to do.

Tonight I have started a new target with CLS filterd Luminance @ 15 mins and will do the full 1600 for the red.

Mike.

[steppenwolf]

That's quite a large percentage increase for the the red channel but it will be interesting to see your final conclusion.

[MikeD]

Totally agree but then again 900 sec's was also a big increase from the Blue and Green.

Like you say it will be interesting to see what happens.

Mike.

[MikeD]

Really surprised there has not been more opinion/advice on this considering the dramatic increase in Ha responce when LP filtering LRGB Data.

Is it reliable to just scale up G2V RGB weighting from 10 second tests to 400 sec's?

Am I losing valuable red signal by Lp filtering the Luminance and at the same time changing the colour result of the weighted RGB data?

Should I consider mixing the red channel with the L?

Mike.

[Starflyer]

All above my head I'm afraid Mike, it's a cracking image though

[ollypenrice]

Fabulous result, Mike. Getting that darned jet nearly killed me so chapaeu, as we say in France!

Glorious resolution at your FL as well.

Olly

[MikeD]

Thanks guys.

OK went back to the raw RGB stack (equal curves applied in photoshop) And the way I rememberd processing it was wrong, I pushed the red but also brought back the black point.

It looks like 900 sec's is too long for the background even if it is closer for a G2V match so 1600 sec's is going to be a mile out.

Below is the combine of the RGB Data with a little equal curves applied to open out the histogram.

Looks like some more experimenting is needed but the colour is soooo much easer to process than when I shoot with no Lp filter.

Mike.