How to stack previously registered images without doing any other operations...
Stacking program, astrometric (plate) solver, fits file viewer
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I have been unable to discover how to do a straight stack of TG images from the S30 Pro wide field camera. The images are already registered and fully aligned using star matching by other software. Is it possible to do a "straight" stack average using ASTAP with nothing else performed on the images? There are 1407 images, which I want to stack in groups of ten.
Last edit: Andy Howell 2026-10-17
Hi Andy,
I do no expect the images alignment is transferable. But group stacking will go very fast. It will align the image on the star pattern. Just try it. See below.
If flats and darks are already applied by an other program then it is better to not select in the tab darks, flats, flat-darks to prevent these are applied twice.
If this does not work for you, ask again.
cs, Han
Hello Han,
Yes, ASTAP stacking in groups works great when the field does not have distractors in the foreground - e.g., side of my house. When there are distractors in the foreground, they confuse ASTAP because it places extraneous quadrilaterals that match highlights that are part of the house, not the sky. Not surprisingly, the resulting image looks confused (attached).
I was hoping there might be a way of supressing star matching altogether. Probably I need to find another way - e.g., cropping - because the end goal is to do photometry, and that can't be done with extraneous objects in the field.
Thank you for your quick reply.
I did not expect the house in the image would confuse the algorithm. Do you have in tab alignment set the "maximum number of stars to use" at 500?
I'm currently working on an improvement in the alignment to remove outliers. If the images do not contain any private information you could share them and I will have a look if there is something to fix it.
cs, Han
Hello Han,
Follow-up. "Star Alignment" not "Astrometric Alignment" in the alignment tab seems to do the trick. The images now match on stars while ignoring foreground objects. (image attached) Not sure why I did not find this before. Furthermore, photometry appears to work well on the stacked image, despite presence of the foreground object. This will be a huge time-saver. Thank you again.