Strange grid over stars. What is it?

[Jezphil]

Please can anyone help explain what the grid is that is appearing over the stars in the bottom right quarter panel of this mosaic (from a blue filter only)? There is a criss-cross effect and I have no idea what has caused this. It appears very subtly in the other frames also.  Thanks in advance.

[7170]

15 hours ago, Jezphil said:

Please can anyone help explain what the grid is that is appearing over the stars in the bottom right quarter panel of this mosaic (from a blue filter only)? There is a criss-cross effect and I have no idea what has caused this. It appears very subtly in the other frames also.  Thanks in advance.

They look like diffraction patterns caused by reflections coming off the microlenses of the sensor. Microlenses don’t have an anti-reflective coating.

Some people recommend trying a different brand of filters, others choose to live with it.

What camera do you have as that will help confirm this as some suffer more than others.

[Ags]

A lovely image, regardless of the grid!

[Jezphil]

On 19/12/2021 at 09:07, Ags said:

A lovely image, regardless of the grid!

Thank you! Here is the finished version.

[david_taurus83]

Are you using an ASI1600 or similar camera with same sensor? This is well known issue with this sensor and bright stars. Yours doesn't look too bad though. I have seen worse! Still a great image. Nice, tight stars!

[Jezphil]

9 minutes ago, david_taurus83 said:

Are you using an ASI1600 or similar camera with same sensor? This is well known issue with this sensor and bright stars. Yours doesn't look too bad though. I have seen worse! Still a great image. Nice, tight stars!

Hi

 

Thanks - I am using an ATIK460 CCD monochrome cam.

[david_taurus83]

36 minutes ago, Jezphil said:

Hi

 

Thanks - I am using an ATIK460 CCD monochrome cam.

Can't say I've seen this effect on mine or any other 460's. Below is a single sub but no sign of microlensing.

[Jezphil]

On 23/12/2021 at 14:51, david_taurus83 said:

Can't say I've seen this effect on mine or any other 460's. Below is a single sub but no sign of microlensing.

Hmmm... looks perfectly clear. Thanks.