AkastroidMosaics
Stitching deep-sky mosaics
Shoot a target in overlapping panels, stack each one, and Akastroid places them by their stars, matches their backgrounds and feathers the seams into a single image, without blending by hand in Photoshop.
Free to try. Your images are not uploaded, and there is no account to create.
When the target is bigger than the sensor
Andromeda is three degrees long. The Veil, the North America Nebula, the Rosette with its surroundings, a stretch of the Milky Way: the targets people most want to photograph are often larger than the field their telescope shows. A mosaic covers them in pieces and puts the pieces back together at full resolution.
Placed by the stars they share
Every pair of panels is compared, and the pairs that share stars form a map of which panels touch which. Positions are worked out along that map, so a panel in the far corner that never overlaps the reference is still placed exactly, through the panels between them. A panel that shares no stars with any other is reported as not connected rather than forced into the picture at a wrong position.
Matching the seams
Panels shot hours or nights apart sit at different sky brightness, and feathering alone leaves a lighter or darker rectangle. So the difference is measured in the overlap itself and each panel is matched to the reference first; then the seams are blended over a width you set. Wider hides a seam more thoroughly and costs a little detail either side of it.
You choose the reference
The panel at the top of the list is the one every other panel is matched to. Drag your best one there (the panel shot highest in the sky, on the clearest night) and the rest are matched to its background.
Panels from other software
The panels can be FITS, XISF, TIFF or PNG, so a set stacked in PixInsight, Siril or DeepSkyStacker stitches just as well as one stacked in Akastroid. If you would rather do everything in one place, each panel goes through the deep-sky workflow first for calibration, grading and stacking, and then into the mosaic.
For planning panels, overlap and how many nights a mosaic really takes, read the guide on mosaics explained.
Do I stack the panels first?
Yes. Stack each panel on its own, in Akastroid's Deep Sky mode or anywhere else, then give the mosaic tool the finished panels. Raw frames from different panels cannot go into one stack: they only partly overlap, so aligning on the shared stars would smear everything else.
How much do the panels need to overlap?
Enough to share a good handful of stars. Around 10-20% of the frame is the usual plan.
Can it stitch a mosaic of the Moon?
Not yet. Panels are placed by matching their stars, and a lunar or solar close-up has none to match, so the mosaic tool is for deep-sky fields. A single lunar close-up that fills the frame is fully supported by the planetary and lunar mode.
Is mosaic stitching in the free version?
Yes, as is every feature. A free copy has five processing runs and two exports; saving the finished mosaic uses one of the exports.