Stars artefacts after creating a mosaic

300% - that is some pixel peeping 😊 

Only thing that comes to mind immediately - you really need 5000, I usually use 3000 at best (although I don't think this has anything to do with your problem.

What is your imaging gear ?

Hi David @dav78,

It looks to me like there is downscaling in play together with Lanczos data interpolation. Are you creating the mosaic using frames with different image scales?

The artefacts migh be avoided by

• using another data interpolation filter, like Cubic B-Spline, or
• preventing the possible downscaling
• or using drizzle integration instead of non-drizzle integration, just enable drizzle, use scale 1.0, droplets of 1.0 and the tophat kernel, that should really give you better stars 😉

Cheers,

Mabula

Hi,

@einari, yes 300% is definitely a huge pixel peeping 😉, the purpose was to show the issue. But looking at the full mosaic, it's not so bad, but some stars have a strange shape. My gear is A7S modified + TS Star 71.

@mabula-admin, thanx for your quick feedback ! The different pictures were just cropped to avoid bad sides, but they have the same scale, at least I think. I will try your solutions and be back here soon 😀 

@mabula-admin,

I tried a few things :

1 - lanczos3 as usual, with the issue

2 - Cubic-Spline : the stars are perfectly round, but much bigger, and very soft, as the background

3 - Drizzle 1 : the better result, with stars just a little bigger than the single stacked frame, but with a softer background

4 - Billinear : similar to drizzle 1, but the stars seem to be a little bigger.

What do you think about those results Mabula ?