Need help to identify the cause of an ugly reflection...

[darkairmouse]

Hi guys,

This is just a quick test shot - 5x240sec, Borg45EDII @325mm, no flattener; 1.25" Astronomik CLS CCD filter, ZWO ASI178MM-Cool.

Noticed that ugly reflection pattern around that bright star.

I had a similar thing before but that was a VMC200L and SBIG ST8300 (microlensing) with an IR pass filter, so microlensing was the one to blame.

Should I blame the Borg45EDII this time, or the filter? 

Thanks!

Yue

[sharkmelley]

It's a microlens diffraction pattern.  There's a similar example from same ASI178MM camera here:

Strange diffraction pattern - Imaging - Discussion - Stargazers Lounge

It's sometimes confusingly referred to as microlensing which of course is an astronomical term meaning something completely different.

Mark

 

Edited January 31, 2021 by sharkmelley

[darkairmouse]

I thought ASI178 doesn't have microlens..Doh!

And thank you for pointing 'microlensing' out to me! Just Googled, haha I can imagine you shake your head when you read my post - '...caused by microlensing...'  😝   

Thank you Mark!

Yue

[sharkmelley]

It certainly does have the microlens diffraction!  In fact the ASI178 was one of the first cameras that we properly analysed:

https://www.cloudynights.com/topic/635937-microlens-diffraction-effect-explained/?p=8967693

Edited February 13, 2021 by sharkmelley