Stretching with Masks

[frasax]

Hi there,

i´ve browsed through several Postings and Tutorials, but couldn´t find the right answers.

I do have an image, which has some blurred stars due to bad focussing, seeing etc. I´d like to mask the stars from the first stretching on. I´ve tried masked stretch script which seems to work nicely concerning the stars, but which is not aggressiv enough to stretch my image to a good point.

So what would be you´re way to solve my problem?

CS Frank

[Geoff]

You could try a star mask (inverted to protect the stars). However, a better way is to throw the images away and re-acquire the data, making sure that you have fixed whatever caused the problem in the first place.  Why try to work with bad data?
Geoff

[frasax]

Hi Geoff,

it´s not THAT bad Data:-)
And i´d like to know in general if masking does make sense at a very first stretch.

CS Frank

[Geoff]

You can use a mask while stretching. However, you will probably have to stretch the mask before you apply it, that is transfer the STF stretch settings to the histogram window, then give a real(histogram) stretch to the mask. Then apply the mask to your linear image. You may need to experiment with the mask stretch.
Geoff

[chris.bailey]

If the stars are not too bad a Masked Stretch (which will tend to limit further star growth) followed by a star mask and some Morphological Transformation can help "hide" the issue


Chris

[Phil Leigh]

The masked stretch script can stretch an image all the way to pure white. I normally find that if I set the target value to 0.25 I am quite close to my final brightness level.
Alternatively you could use the new MaskedStretch process... set the number of iterations to 1,000.

[Warhen]

Phil, Did you mean as high as 1k iterations? Thanks!