Removing gradients in widefield pics

[virtualpilot45]

This is my first DSS widefield pic and I don't know how to remove the red gradient in the bottom left and the blue gradient in the top left without affecting the image aversely.

Any help would be much appreciated

Cygnus | Flickr - Photo Sharing!

[Uranium235]

Ive had a go with noels actions to fix this but it was a no-go. I dont think its an LP gradient and looks more like amp glow than anything else. Amp glow can really affect the final image if youve been using live view beforehand. If you have to use it (for focusing etc..), it might be best to let the camera cool down for a few min before you start taking subs.

[Psychobilly]

What model Camera is it...?

Taken a few darks will help a lot.. but firstly you need to experiment to see how the "Glow" changes with the number of exposures and the gap between thm..

My Nikon D200 which I love for general use, used to suffer from ampglow , it would take around 10 shots to Stabilise so that darks could effectively remove it, and that was leaving half the exposure duration between each captured frame

Peter...

[ollypenrice]

Some bought software solutions;

Pixinsight, (Dynamic Background Extraction and Background Neutralization.)

Photoshop Plug In, Gradient Xterminator by Russ Croman.

Olly's Bodges for Photoshop (or similar);

Feathered lasso to include the red zone plus a bit. Curves. Select each colour channel in turn and pin the curve at the healthy background level. Click on the brightest red to fix that on the curve. Drag that point down to the background sky level. Repeat for each colour.

As above though, avoid it in the first place if you can.

Olly

[steppenwolf]

This looks very much like amp glow to me. Take some matching DARKS and subtract them from your image. Failing that, Gradient Xterminator has just done a good job of it on my PC.

[Psychobilly]

In this case where the color gradient was just over a starfiled ..

I used the Color Selection method, dropped the saturation and adjusted the intensity of the selection to match the background...

It wouldnt work so well if it was on a DSO though...

[virtualpilot45]

Hi, thanks for all the suggestions. My camera's a Casio EXZ850 and come to think of it, I did have the LCD switched on for all except the last 1/4 of exposures. The top light may be caused by the little green activity LED on near the viewfinder. I'll try doing some darks too next time.

Since I haven't much money to spend on new software/equipment, I followed Psychobilly's advice for the colour removal, then added an additional curve to remove the noise all around the picture, all on GIMP.

[Psychobilly]

The way I suggested is quick and dirty but only works for starfields.. its not to hot on nebula's or anything "colorful"...

But you seemed to have sorted it out a treat

[ollypenrice]

Indeed!

Olly