Author Topic: Best settings for Photometric Color Calibration of M42 and M43 widefield  (Read 704 times)

Offline Rudy Pohl

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I'm quite new to using PCC and can't get it to produce an acceptable result on my widefield of M42-M43. I have chosen a G2V Star as my white reference and think that might be the problem. I have all the other parameters filled in properly (I think).

Problem is I keep ending up with the background being predominately red or pink.

Any suggestions what I should use for the white reference?

Thanks,
Rudy

Offline pfile

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well the area is full of brown/red dust, so there is that. i think for anyone to help you might need to post the images.

rob

Offline Rudy Pohl

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Hi Rob,

Thanks will do. I have redo one first as I chucked them all out.

Rudy

Offline monkeybird747

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Have you tried the Average Spiral Galaxy model? G2V is biased toward reds. Maybe check the spectral types of the predominant stars in the trapezium and try a model that is similar?

Could you tell us the type of frames being used (OSC, LRGB, etc.) and at what point in your processing you are using PCC?


Online ngc1535

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I'm quite new to using PCC and can't get it to produce an acceptable result on my widefield of M42-M43. I have chosen a G2V Star as my white reference and think that might be the problem. I have all the other parameters filled in properly (I think).

Problem is I keep ending up with the background being predominately red or pink.

Any suggestions what I should use for the white reference?

Thanks,
Rudy

Rudy,

Did you select background neutralization? This will take care of the offsets between your color channels. Otherwise your image will indeed be dominated by the an offset of brightness in whatever the offending channel it happens to be in. 

-adam

Offline Rudy Pohl

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Hi Adam, Rob and monkeybird,

Sorry I've been so unresponsive, I've been unavailable for a couple of days but I'm cleared away now.

After getting notice of Adam's post a short while ago I ran PCC again with the suggestion that have been made above (using Average Spiral Galaxy and Background Neutralization) and the resultant imaged looked quite good with no colour cast.

Thanks very much guys,
Rudy

Online ngc1535

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It does getting tiring being wrong so frequently...I am so happy to have gotten one right!
lol
Now that you know that option is available- a couple of notes.
1. You can refine the window of background brightness by lowering the Upper Limit. .1 is actually a relatively high value.
2. Even better...is do not worry about it and use the region of interest from a preview. If there aren't *crazy* gradients in your image- then you can choose a bit
    of sky you know is neutral in color. It might be necessary to display the image by unlinking the channels and applying autoSTF.
Anyway... a couple of ideas.
-adam