black pixels around stars after StarAlignment?

[ctemple]

Hi all - fairly new to PI and have just experienced a strange issue.  I have examined my subs of R, G & B frames that we took last night after calibration and they all look fine.  However, after performing a StarAlignment, the subs now show black pixels around several of the stars (almost look like halos).  Nothing else was done other than the alignment.  Any ideas what could be causing this?

Thanks in advance!
- C&T

[Carlos Milovic]

Change the interpolation algorithm to bicubic spline, or change the clamping parameter.

[ctemple]

Hi Carlos,
Thank you so much!  I wound up changing to bicubic spline as well as lowering the clamping parameter to 0.15 to remove them all.
Really appreciate the help!!
- C&T

[pfile]

is this a widefield image? i usually only see this ringing on hot/warm pixels but my image scale is 1 arcsec/px.

[Geoff]

I've seen it at 2" per pixel. Bicubic spline removes it.
Geoff

[jeffweiss9]

C&T-
 Just noticed your post but I have this problem invariably with my 2x2 binned RGB.  The solution I use, as already stated, is to go to cubic bilinear interpolation with a damping factor of 0.1 or 0.15.  I use the Automatic (Lanzlos3) with all unbinned subs (L, Ha) with no problem.
Clear skies,
-Jeff

[ctemple]

Thanks Jeff!  This was indeed binned 2x2 so maybe that's something I have to watch for in the future.  For the L I left it as "auto" and it didn't display the same issues (it was binned 1x1).

Thanks again for all of the help!

- C&T