Blue Cast to one side of image

[JohnC64]

Ane one have any idea what has might be causing the the blue gradient over this image of the Rosette Nebula. It wasn't the moon or any local light pollution. Everything was looking good during capture. I have tried various stacking/processing techniques but cant get rid of the gradient.

The full stacked FIT is at https://dl.dropbox.com/u/49530954/rosette_stack.fit if anyone fancies a play with the original.

Any ideas gratefully received.

Cheers John

[Spikey]

Could be light leaking in somewere John.

[Welrod50]

Did you block off the viewfinder? Looks like some sort of light interference to me, even more so that it is biased to one side of the image. Also, are you using flats and were they evenly illuminated?

Just a few ideas

[JohnC64]

Ah the viewfinder could well be the culprit - good one.

Cheers John

[cosmojaydee]

had a little play

[Spikey]

Just spent 10 mins playing with the .fit and this is the result

[JohnC64]

Nice one CosmoJayDee - Ta John

[rfdesigner]

I think I'm going to point the finger at your flats.

How did you take them (I wondering if you used a laptop screen, which might have had slightly variable colour cast)

Derek

[JohnC64]

And cheers Spikey too

I'm well out of practise with my Setup routine and my processing skills. Back to basics for me i think and try not to rush my setup 'cos we have one of those rare elusive beastie - a clear sky!!

John

[Spikey]

I'm sure someone who knows what they are doing will do a better job;

In brief I have;

Aligned the RGB channels

Adjust levels in each channel

Couple of Curves and drop the black point

Increase saturation

High pass filter - high setting, blend overlay

Gradient xterminator - fine setting/weak aggressiveness

Make stars smaller then Increase star colour

Noise reduction

Hasta la vista green - setting medium

Saved as a PNG as 25% size, posted here

[JohnC64]

no flats is this stack rfdesigner - when i had trouble, i pruned everything back to just a stack of subs and when i still had problems guessed it was in my original subs.

Cheers John

[JohnC64]

Aligned the RGB channels

Adjust levels in each channel

Couple of Curves and drop the black point

Increase saturation

High pass filter - high setting, blend overlay

Gradient xterminator - fine setting/weak aggressiveness

Make stars smaller then Increase star colour

Noise reduction

Hasta la vista green - setting medium

Yup think i will need to invest in photoshop to improve my picture bashing skills

John

[Spikey]

Yup think i will need to invest in photoshop to improve my picture bashing skills

John

You could achieve exactly the same in GIMP John and it's free.

[cosmojaydee]

A little more subtle

[ollypenrice]

DBE and SCNR Green in Pixinsight would make light work of sorting this gradient out without damaging your general colour detail. I used to get a slight red-green diagonal gradient in my Atik 4000 OSC and cured it this way in a few seconds. It's worth having PI just for DBE, quite honestly.

Olly

[dmahon]

There was an old free version of Pixinsight that did DBE - unfortunately now very hard to get hold of.

[james_screech]

Could it be possible that you've got a ground loop in your imaging system?

I've seen similar issues when there are more than one ground connection between a camera and computer (using same battery and having a USB connection). If so, try running the computer and camera from different power sources so the only ground connection in common is via the USB connection.

James