DBE / background neutralization if there is no background?

[cmarcus]

Something I have always wanted to know, but been too embarassed to ask... what if your image has no background sky, it's a close up of a big nebula object for example. How do you do DBE/background neutralization and colour calibration?
TIA

[ChoJin]

someone asked this last week, take a look there:

http://pixinsight.com/forum/index.php?topic=10185.0

[sreilly]

Comes back to a question I have on how does STF get a very close approximation to a good color balance when the color channels are unlinked? Why can't that replicated and then tweaked with Histogram Stretch for the individual color channels? Obviously there is a means to do this, jut not obvious to me I guess. See this thread as well http://pixinsight.com/forum/index.php?topic=10245.0

Steve

[Greg Schwimer]

Comes back to a question I have on how does STF get a very close approximation to a good color balance when the color channels are unlinked? Why can't that replicated and then tweaked with Histogram Stretch for the individual color channels? Obviously there is a means to do this, jut not obvious to me I guess. See this thread as well http://pixinsight.com/forum/index.php?topic=10245.0

Steve

It can... simply drop the STF triangle at the bottom of HT and apply HT. This will bring the unlinked settings from STF over to HT, which you can then use to stretch the image.

[sreilly]

That's fine if you stretch your images with HST but I prefer to use Masked stretch for a stellar profile I like better. All I want is to get the color correct and then stretch by the means I determine to be best for the image. I get larger stars in HST than with Masked Stretch. Just saying, I think I have better control over the process this way.

Steve

[Greg Schwimer]

Right. I also find MaskedStretch does better with stars. In this case you'll have to use BackgroundNeutralization and ColorCalibration to prep the image for MaskedStretch.

[msmythers]

Steve

AutoSTF sets the median value of the channels to very closely the same value. Of course it stretches the image also. You can get the same results or very close to STF but not stretched by using AutoHistogram and statistics. Open Statistics and chose the median value of a channel. I generally would use the highest of the channels to be sure not to clip the minimum. Use this value to set the median value in AutoHistogram and execute. You now have a median value balanced image just not stretched.

Here is a screen shot with statistics for my image and AutoSTF unlinked. The second image is after Autohistogram and linked STF.

Mike

STF was not active for autohistogram image when I captured the screen. Here is the image again and showing the correct AutoSTF linked.