Different star size

[Ceph]

I recently bought a ZWO ASI 1600MM pro and have taken say 8 complete pictures with it now.

Now and then I notice that the star size suddenly can change, inspite of me not touching anything. It can happen in the middle of a picture seqeunce.

I use Astro Photography Tool to run the camera.
Pictures below is 50 s LUM, took around 60 pictures in a row and had to remove 8 of them that had larger stars like the left pic is showing.

I have seen this a couple of times now and wonders what it could be and if I can fix it somehow?

[Dr_Ju_ju]

air pressure, wind, both high & low, clouds you may not even see, especially high ones, take your pick....  that's why we take multiple images & stack

[Ceph]

1 hour ago, Dr_Ju_ju said:

air pressure, wind, both high & low, clouds you may not even see, especially high ones, take your pick....  that's why we take multiple images & stack

Thanks Julian

I was thinking about thin clouds but at the same time I was worried about the camera,

[Dr_Ju_ju]

Also unless you took all the pictures at the same time, the volume of air above the camera will either lessen or increase with rotation...

[Adam J]

On 19/09/2020 at 09:35, Ceph said:

I recently bought a ZWO ASI 1600MM pro and have taken say 8 complete pictures with it now.

Now and then I notice that the star size suddenly can change, inspite of me not touching anything. It can happen in the middle of a picture seqeunce.

I use Astro Photography Tool to run the camera.
Pictures below is 50 s LUM, took around 60 pictures in a row and had to remove 8 of them that had larger stars like the left pic is showing.

I have seen this a couple of times now and wonders what it could be and if I can fix it somehow?

yep this is not the camera, its a thin cloud drifting through your fov and then back out, due to auto stretch you will just see a slight dimming of the stars. Nothing to worry about.