new to LRGB processing question

[graham.hobart]

So I stacked my LRGB frames in Maxim DL and have the finished product -I did a quick process in Star Tools and it has a greeny hue to some of the nebulosity. My RGB frames were all the same duration.
Any idea ?
Graz

[rcheshire]

Graham. Pretty sure it's the remnant of debayering. I see this with Pixinsight.

Ivo should be able to tell you how to remove "green noise" with StarTools.

[Peter.M]

Im guessing with him saying that his RGB exposures were all the same that he isnt using a OSC camera and so there is no debayering. If its anything like my RGB data the excess green can be processed out in photoshop or something similar. I use the colour balance tool and drag the green towards the magenta. Alternatively you can stretch the other channels more to increase them.

I dont combine the L in maxim though, just the RGB. Then I take the combined RGB and L into photoshop and process it in there.

[graham.hobart]

Thanks geezers, should have also mentioned used a LRGB/H alpha routine. But what everyone says makes sense. Will publish the original processed picture and the next one with advice heeded.
Need to sort it out now.
Graz McTaz

[rcheshire]

Sorry Graham. Of course it's LRGB - didn't correlate. Never mind, just losing it.

[irwjager]

Hi Graham,

To get rid of any green hues in ST, lauch the Color module and set 'Cap Green' to 'Yellow' or 'To Brown'.

Not sure if you have taken this into account, but do keep in mind that even though your frames are all the same duration, the actual light gathered per filter can vary substantially. Therefore you should find out the right ratio to multiply your exposure times by for your particular filter set and CCD sensitivity for the different wavelengths.

If you don't know the right ratios, you could find out by calibrating against a known object (for example a G2V star).

Cheers,

[graham.hobart]

Here is 87% image -in Star Tools my version says Cap green yes or no only.
Thanks for any advice
Graham

[irwjager]

If your image is a widefield with enough stars, then another trick you could use is calibrating against the aggregate of starlight in the image. The rationale here is that, on average, starlight is white.

So, in the Color module, I created a starmask and clicked the 'Sample' button. This tells StarTools to calibrate against the currently selected mask. For your image, StarTools decided on a 1.83 Green multiplier and a 1.48 Blue multiplier in order to calibrate the image. To apply the found multipliers to the full image (and not just the star mask) you just reset the mask to the full image again (Mask->Clear, Invert).

You'll notice the stars are now much more varied in colour and span the full range of temperatures - a sign we're on the right track.

I noticed the Trifid's core was a bit greenish, so I set Cap Green to 'Yellow'. You'll find this functionality in the (stable) 1.2 Beta.

Of course you could season to taste, but it's one way of performing colour correction by means of 'science', rather than the seat of your pants. :P

To isolate the nebula from the somewhat noisy background and large amount of stars, as well as to give it a bit of depth, I used the Life module with the Isolate preset.

Cheers,

[graham.hobart]

Nice one! will try that out later