saturated pixel in black rather than white

[Jan Kohnert]

Hello,

while moving our pipeline from astrometrix to scamp I got some warning from swarp version 1.X and so updated it to the newest version.

Unfortunately now the satuated pixel are white in the combined images, while they used to be black with the older version.

A collegue of mine told me, he had seen that phemomenon himself and so decided to to upgrade to get the black pixels, as he found no way to fix the problem.

So here's my question: is it possible to get saturated pixel in black? And if yes, how can it be configured? I found the parameter PIXELSCALE_TYPE in the documentation, but I don't know, if this could be the solution...

Best regards Jan

[Emmanuel Bertin]

This may have to do with pixels having zero-weights. Do you give to SWarp weight-maps in input? If this is the case, you may have decided to give saturated pixels a weight of zero. On the request of users, it was decided that pixels with zero-weights are not blanked during the coaddition process if there is no over overlapping image at the current position. May be this is what you see.
If you think that this is the likely explanation, I can certainly add a new option to Swarp so that it will behave like in older versions.
Emmanuel.

[Emmanuel Bertin]

The latest version of SWarp (not yet released, but you can get the development version from here) has a new option BLANK_BADPIXELS, which allows you to activate the blanking of bad pixels in the coadded image.
Emmanuel.

[Jan Kohnert]

Hi Emanuel,

I think, the explanation is exactly the thing I see.

I will try the devel-version and see if it resolves the problem.

Thanks for your great work.

Best regards Jan

[Emmanuel Bertin]

The new release should happen very soon now (this evening or tomorrow). I had to delay it because of a huge bug I introduced in the image combination part.
Emmanuel.