whats this?

[smr]

hi,

just stacking some data together and wondered what's causing this, from data over multiple nights. 

some of the stack was before i got my bahitnov mask and was able to focus properly... some of the stack is with the mask. Would this be why the stars have this strange pattern around them?

Edited January 25, 2020 by smr

[CloudMagnet]

Looks like it, if the focus was off the other night by not using the mask, the stars will show as bigger in your images. So when you layer them together, you get that effect of a two-tone star. One way to check is to stack the each nights images separately and the effect should disappear- this rules out any other issues.