Strange artifacts around bright star Alnitak.

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John_Gill
Posts: 9
Joined: Wed Jan 23, 2019 6:33 am

Strange artifacts around bright star Alnitak.

Post by John_Gill » Wed Jan 23, 2019 6:42 am

Hi,

Kindly refer to the attachment. This was my first attempt at narrow band - shot with an APM apo 107/700 scope with the new ZWO 1600MM cooled to zero degrees, exposure 300 seconds at gain 100. There are two issues, the first is the bright star halo and then star itself is reflected around itself.

Any tips, suggestions, ideas would be most welcome.

space is not black
John
Attachments
horsehead_Ha_crop.jpg

Katherine.Tsai
Posts: 66
Joined: Fri Dec 07, 2018 10:24 am

Re: Strange artifacts around bright star Alnitak.

Post by Katherine.Tsai » Thu Jan 24, 2019 2:44 am

Hi John,
I am sorry about the problem you are going through.
I have to tell you there is no way to solve this problem now.:(
This model of sensor (Panasonic MN 34230) does not have AR coating, so it has the possibility to show reflections of the bright star, and not only 1600MM, all cameras which use this model of sensor have such problems.

we've raised our suggestion to the manufacture, but the sensor factory does not care about the astronomy market: (
it's a small market compares to others.
So we do not have idea how to solve it right now.

John_Gill
Posts: 9
Joined: Wed Jan 23, 2019 6:33 am

Re: Strange artifacts around bright star Alnitak.

Post by John_Gill » Thu Jan 24, 2019 6:36 am

Hi,

So can I get a refund for the ZWO1600MM, Filter wheel with LRGB and NB filters? This was purchased at the end of December and used only once.

Regards
John

DaveFrance
Posts: 22
Joined: Mon Oct 15, 2018 7:56 pm

Re: Strange artifacts around bright star Alnitak.

Post by DaveFrance » Thu Jan 24, 2019 3:09 pm

If it is the 1600MM Pro then the ZWO website says it has an AR protect window. If AR is the problem should that not prevent it?

https://astronomy-imaging-camera.com/pr ... 600mm-cool

John_Gill
Posts: 9
Joined: Wed Jan 23, 2019 6:33 am

Re: Strange artifacts around bright star Alnitak.

Post by John_Gill » Thu Jan 24, 2019 3:47 pm

Hi,

Yes it is the pro "Cooled" version

Regards
John

DaveFrance
Posts: 22
Joined: Mon Oct 15, 2018 7:56 pm

Re: Strange artifacts around bright star Alnitak.

Post by DaveFrance » Thu Jan 24, 2019 3:51 pm

In fact all the 1600 cameras with Panasonic sensor are listed with AR protect window.

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chad
Posts: 584
Joined: Thu Feb 09, 2017 4:58 am

Re: Strange artifacts around bright star Alnitak.

Post by chad » Fri Jan 25, 2019 1:22 am

Hi Dave,
Sorry for the problem.
I noticed the problem you point out. I think there is a misunderstanding.
On our website: we used AR window as the protected glass. You can touch it when you lift the dust cover from the camera.
Usually, if it's not AR glass, just common glass as the protected glass, the halo problem is much worse. It affects the whole target. Not only the light star. So do not worry.
Thanks
Chad
ZWO Driver Engineer
Location:lon=120.6 lat=31.3
SuZhou China

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chad
Posts: 584
Joined: Thu Feb 09, 2017 4:58 am

Re: Strange artifacts around bright star Alnitak.

Post by chad » Fri Jan 25, 2019 2:14 am

John_Gill wrote:
Thu Jan 24, 2019 3:47 pm
Hi,

Yes it is the pro "Cooled" version

Regards
John
Hi John,
Sorry for the problem again.
First of all, thank you very much for choosing our camera.
For the halo, Dave's post is true. We used AR widows as the protected glass. It is also to prevent halo. As we know, Halos are caused by the refraction and reflection of light in different media. So, the AR window only could prevent the halo before the light reaches the image sensor.
But inside the image sensor, it also have a series of glass, like micro lens, protected lens and so on. So when the light enters the Sensor, the lenses inside the Sensor will also cause this problem. Preventing these glasses from creating halos is also a very complex technology. All of us know a AR coat is needed. But beside that, we knows nothing. We talked to the engineer of Panasonic before, they also have many questions about how to implement it. Hope you can understand.
For the problem, as you know, ASI1600 is one of the most widely used cameras, not our customer, include ourself, we all have similar problems. According to our experience, usually, when they meet this problem, usually, they will reduce the exposure time and gain, then take multiple shots, and finally stack them together to reduce the halo. After that, with calibration, the halo is usually reduced to an acceptable level. You can have a try.
Thanks
Chad
ZWO Driver Engineer
Location:lon=120.6 lat=31.3
SuZhou China

John_Gill
Posts: 9
Joined: Wed Jan 23, 2019 6:33 am

Re: Strange artifacts around bright star Alnitak.

Post by John_Gill » Fri Jan 25, 2019 6:01 am

Hi,

The halo is a small part of the problem which I can remove with processing. The big issue is the "micro - lens" effect on bright stars, in this case Alnitak. Perhaps the issue is more about the Ha filter.

Regards
John

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chad
Posts: 584
Joined: Thu Feb 09, 2017 4:58 am

Re: Strange artifacts around bright star Alnitak.

Post by chad » Fri Jan 25, 2019 7:09 am

Hi John,
The "micro - lens" effect is also a kind of halos, They have the same reason. According to our test, Ha filter will be better.
In a word, reducing the intensity of light at each shot is a very effective method.
Thanks
Chad
ZWO Driver Engineer
Location:lon=120.6 lat=31.3
SuZhou China

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