Hi Courtney,
The stack align feature works best when you select stars to centroid on in images. If your galaxies are bright enough and your aperture size encapsulates most the the galaxy, that should work as well. If your galaxies are faint, try using nearby stars as the
sources for alignment. Another potential problem is that if the images are shifting by more than the aperture size, the centroid operation may fail to find the star. If that is the case, try enlarging your aperture radius to capture the alignment sources,
even with the image shift, but be careful to not make it so large that it captures neighboring stars.
An alternate solution is to "plate solve" your images (add WCS headers to the images), if not already done, and then use the WCS alignment option in stack aligner. That option uses the WCS header info to align the images and does not require any source apertures
or centroid operations.
Let us know if one of those possible solutions helps,
Karen
On 4/30/2018 11:29 AM, courtney13 [via AstroImageJ] wrote:
I'm trying to stack some pictures of a galaxies but need to align them before combining into one image. I'm trying to use "align stack using apertures'. It worked for the first galaxy
but now after I click to put the apertures on the photo I get the following message:
***ERROR: No signal for centroid in aperture C4 of image MCT20_1803260108_out.fits.
********: Measurements are referenced to the non-centroided aperture location
I've gone back and tried the first galaxy I did again and it comes up with the same message even though previously I managed to do this. Does anyone know how to resolve this?
Locked
