QHY9m odd star shapes and lines

[jwoody]

Hello all
I am getting some what looks like spikes in the brighter stars from my camera. They also appear to be a little bit squared off.
I didn't have the problem with my old QHY8pro so I am ruling out the scope.
I don't think I had the problem with just the QHY9 without the filter wheel.
So I am left with just the filters but I am not certain. I thought I may have over tightened the filters in the wheel causing some pinching but a checked the tension on them all and seemed fine.
Using a Tak 85,QHY9 (gain 23 offset 73)and baader 36mm LRGB in a QHYcfw2.
Any ideas?
Thank you
Jeremy

[Shiraz]

http://www.cloudynights.com/topic/387355-microlens-effect-on-8300-ccds/
maybe?

[jwoody]

Thank you Ray

[RickS]

I have been accused of adding fake diffraction spikes to images taken with KAF-8300 sensors :)

[Slawomir]

It was more of an inquiry rather than accusation, and a result of my ignorance...:whistle:

[gregbradley]

Yes Microlens artifacts. I do not recall seeing them though with my old FLI ML8300. But that had no cover slip so perhaps its more likely then to be an interaction between the cover slip and the microlenses.

Sometimes the thickness of the sensor stack (sensor, microlenses, cover slip, CCD window etc) causes unwanted reflections.

I also wonder if the CCD window has no antireflection coatings (probably does not). FLI researched the reflection coatings on the ML8300 and improved them after one user complained I think of halos on some stars.

The microlenses though increase QE a lot so you are better off with them.

Greg.

[RobF]

Yes, Marc (Multiweb) explained this to me earlier in the year.

At the time I was comparing M33 data we both shot at Qld Astrofest through FSQ106s. My data with QHY9 (with microlenses), and Marc's with QHY8 (without). Concerned why my FSQ had diffraction spikes!

Example image here:
https://picasaweb.google.com/UserRobF/DropBox?authkey=Gv1sRgCM_sxYnn5IGJr wE#6188366930876545234

(left is super zoomed in QHY8, right is same FOV QHY9)

[RickS]

I wasn't thinking of you, Suavi. Your comment, IIRC, was definitely more of a question rather than an accusation :thumbsup: :) Others have been less kind.

[Slawomir]

No worries Rick, I was just having a giggle. As for the spikes, I am pretty sure that when I was closely examining my images I noticed some tiny but definite spikes in some stars in my photos taken with a doublet and ICX814. So perhaps as Greg mentioned, sensors with microlenses introduce such spikes to various degrees.

[jwoody]

Thanks for your help, I don't really like the effect but I will just have to live with.
Cheers
Jeremy