How to grab RGB

[blinky]

OK I aqm planning on trying to grab some RGB data tonight for my M101 mini project! So....

Do I need to make the subs longer, shorter or the same as each other and as the original Greyscale data that I will be using as Lum?

Should I leave my LPR filter in place even when imaging with the coloured filters? My guess is Yes as I will staill have some form of light pollution????

Finally should I bin the colour images and if so how do I then add them to the Lum as it will be at a diffrent image scale, or am I missing something??

Hopefully by the end of tonight i will have my first LRGB image

[Aza]

Not sure of the answers, but would be interested to hear them

Been thinking about these questions myself, in case I ever get a CCD!

[Parallax]

Last question first.

If using DSS, then tick the "2 x drizzle" box. This will double the image scale (if binned 2x2). Alternativelly, increase the image size, after stacking etc, in your photo package s/w.

Can't advise on LPR.

Being fairly new to this RGB game, I can only tell you what I do. The RGB subs will need to be at least as long as the Lum OR bin them. For example, for a 5 min Lum sub you could do 3 min binned RGB subs. It is a bit of trial and error.

Caveat: I could be totally wrong!

Steve

[RobH]

If you leave your subs binned 1x1, leave them the same exposure as your luminance.

Binning 2x2 doubles the sensitivity, and halves the resolution.

I'm working on some targets (M101 included) at the moment where I'm grabbing 6 minute luminance subs, and doing 4 minute 2x2 binned RGB ones.

I shot some 2x2 Ha last night, but kept the exposure to 6 minutes due to the fainter nature of the Ha emission.

Personally I don't use a LPR filter, but my LP isn't too bad, especially near the zenith.

If you have bad LP, leave it on.

Good luck tonight

Cheers

Rob

[roundycat]

just a thought. My flat exposures vary from about 0.2s L to 10s or more for B. I know that does reflect the spectral output of a tungsten filament to some extent but it also reflects the spectral sensitivity of the camera and filters. According to SBIG I should be exposing in the ratio 1:1:1.6 RGB. That will obviously vary with camera and filters.

I would forget binning for the moment and merely expose as normal but at least twice as long for R and G as for L and maybe even longer for B. All sorts of things will muck up filter factor calculations not least atmospheric extinction which admittedly will not be a problem for 101.

Dennis

[RobH]

Good point about spectral sensitivity Dennis.

My camera tends to be about the same for green and blue, and probably 10% more sensitive to red.

I bear this in mind when colour balancing during processing, and I tend to bring the red down, rather than boosting green and blue, as this helps keep noise down.

Cheers

Rob

[blinky]

very interesting.. will see how tonight progresses!