Micro lens issues with ASI 1600MM??????

[Merlin66]

Can't seem to find a definitive thread on this subject....
Can someone point me in the right direction.
Just interested - I use the ASI 1600 for solar imaging and now looking at spectroscopy.
Thanks,
ken

[Atmos]

There hasn’t been too much done on IIS but it has been modeled extensively on CN.

[bojan]

http://www.iceinspace.com.au/forum/showthread.php?t=177879
https://www.cloudynights.com/topic/646966-zwo-asi1600mm-pro-bright-star-issue/

[Merlin66]

Ok, but....
Why is not not seen on all sensors with micro lenses, and on all brighter objects within the FOV?
I’m pretty sure if this was a real problem, many commercial cameras would be affected.

[Atmos]

The problem is that this particular Panasonic sensor doesn’t have an AR coating on the cover glass so the reflections are coming from light bouncing between the micro lens and the cover glass. This is why there coming from 0.3-0.5mm above the sensor.

My understanding is that the only way to fix this would be to scrape off the cover glass without hitting the micro lens layer and installing a new cover glass with a AR coating on the sensor side of the glass.

The KAF-8300 ends up with something that looks like diffraction spikes caused by the micro lens.

[Merlin66]

Colin,
From what I can find (google cameras with micro lenses) there are many CMOS chips - I think almost 100%.
Not one of the various links I can find address the reflections from the microlenses to the chip cover plate.
I honestly think if this was a serious issue it would have been raised in commercial camera applications.......

[The_bluester]

I suspect it is is only really highlighted in astro applications. In a different setting the micro lens artifacts will probably be hidden by other bright features on the image.

[Atmos]

I think this is largely a failing of Panasonic here rather than CMOS sensors one general. Don’t have AR coated chips that mitigate this issue.

https://www.cloudynights.com/topic/635937-microlens-diffraction-effect-explained/

This thread among other posts from Sharkmelley and Freestar8n in other threads go pretty deep into calculating and proving where the reflections are occurring and how they’re being created.

This issue seems to largely be exclusively with this Panasonic sensor rather than a systemic issue with micro lens on CCD & CMOS sensors.

[Merlin66]

I finally tracked down the source of the images.
I found these microlens examples were taken from >3 hour exposures!!!!! of bright stars Anitak (mag 1.74) and Gamma Cas ( mag 2.15).
I think that would push many cameras to their limit.

[Camelopardalis]

I didn’t realise it would expose for that long...I thought the driver limit was 2000 seconds :shrug:

[Atmos]

Orion Nebula ( https://www.astrobin.com/full/321338/0/)
The above image shows how easily they can show up.

[The_bluester]

Images like that have been what has kept me from looking at the ASI1600 and others with the same chip.

[Merlin66]

Hmmm
the Panasonic MN34230, used in many popular astronomy cameras, I agree seems to have issues with long exposures (the Orion neb image was 2.2hrs..) of bright stars.

The reason for my interest is the fact that I use the ASI 1600 to image the brightest star in the sky (mag -26!) and regularly over expose the image to bring out faint prominence detail. I was concerned that these artefacts would impact on my ability to image this faint detail - so far that doesn't seem to be the case.

[Atmos]

Those patterns show up in single frames so it doesn’t make any difference with the total integration. Confirmation bias ;)

As for solar, I don’t imagine it’ll matter because you’re not dealing with a point light source :)

[Merlin66]

OK :sadeyes:

The bright solar edge must be causing a certain amount of reflection issues micro lens/ cover plate - which I assumed would impact the image of nearby fine faint detail.

[Loupy31]

Hi Guys, just a quick question if i may, how do you tell the difference between the new filters and the old filters.

thx, peter