Photometric colour calibration tooooo Blue

[pscammp]

Photometric colour calibration = Very Blue image !

Any of you guy's know what might cause this   ??

M42 integration

Image look very blue after the process, using the Readout Mode tool shows that the reds are really close to zero
but the blue & green channels look more normal.

Just curious at this time

Cheers
Paul

[drmikevt]

It sounds like you need to experiment with the white reference setting.  As M42 is not an 'average spiral galaxy', this default setting may not be optimal for that object.  The issue is - with about 50 choices, which star reference will give the best results?  Maybe try researching some of the larger stars in image and use the setting associated with those...?  As you know, it early days with this process, which means a lot of trial and error....

Also - are you using a background reference preview?  This may help a lot.

Mike

[Juan Conejero]

The average spiral galaxy white reference is perfectly valid for *any* deep-sky image, including M42. PCC computes and applies an absolute white balancing, so the reference object does not have to be present in the image; please read the PCC tutorial for more detailed information.

Photometric colour calibration = Very Blue image !

Are you working with a calibrated linear image? Without taking a look at the linear image, we can't say anything useful.

[drmikevt]

Juan

I understand all of that.  But then, why have the other white reference options?  Having those options present implies that a different setting may be best for a specific image.  Others have 'complained' about images being too blue and have found different/better results with different white references - this is the basis for the advice above.  Are you saying that if the spiral galaxy reference does not work well, then the operator is doing something wrong?  Your comment seems to say that trying different white references is not the way forward when the image colors are perceived as 'off', but assuming correct usage of the process, what other means are recommended?

Mike

[dpaul]

Excuse my inexperience here but just wanted to share my recent experience with PCC. I am always using a reference image and some of the time I too get very blue and quite dark results. However, when I then do a histogram transformation, the colours seen to come to a sense of normality.
So it doesn't see to be a problem.

Thanks

David

[pscammp]

The average spiral galaxy white reference is perfectly valid for *any* deep-sky image, including M42. PCC computes and applies an absolute white balancing, so the reference object does not have to be present in the image; please read the PCC tutorial for more detailed information.

Photometric colour calibration = Very Blue image !

Are you working with a calibrated linear image? Without taking a look at the linear image, we can't say anything useful.

Yes Juan,  it is a calibrated linear image. After final integration I applied Dynamic Crop, BN, a bit of DBE before attempting to apply PCC

I am going to load this image up to Dropbox in the morning. I will supply a link and what settings I used in PCC

Thanks
Paul

[pscammp]

Ok so I have discovered one interesting thing......

If I do Background Neutralization using the existing standalone tool (default settings with a preview reference), then run PCC with 'IT'S' BN disabled,
I get this huge blue cast and all the red in the image is almost removed.

If on the other hand I use PCC's BN instead and using the same preview and default settings I don't get the blue colour cast

?

[bob_franke]

Ok so I have discovered one interesting thing......

If I do Background Neutralization using the existing standalone tool (default settings with a preview reference), then run PCC with 'IT'S' BN disabled,
I get this huge blue cast and all the red in the image is almost removed.

If on the other hand I use PCC's BN instead and using the same preview and default settings I don't get the blue colour cast

?

Yes, PCC is always going to introduce a color cast to the background. Start with a flat neutral background then run PCC with BN enabled.  This way, PCC will correct the background color cast that it creates.

Cheers
Bob