Diffraction patterns 1600mmpro + ZWOEFW +RGB filters

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brandxlb
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Diffraction patterns 1600mmpro + ZWOEFW +RGB filters

Post by brandxlb » Thu Dec 07, 2017 9:46 pm

i'm newbie with the 1600mmpro plus ZWO EFW and ZWO RGB filters. i've been getting strange diffraction patterns around bright stars. I have the camera screwed directly into filter wheel which contains 1.25" mounted ZWO RGB flters. Any suggestions gratefully received
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asi1600mm+zwoefw+ZWO RGB.JPG

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Sam
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Re: Diffraction patterns 1600mmpro + ZWOEFW +RGB filters

Post by Sam » Tue Dec 12, 2017 1:26 am

this is because sensor is not coated
there is no way to fix this issue
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Kubaman
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Re: Diffraction patterns 1600mmpro + ZWOEFW +RGB filters

Post by Kubaman » Fri Dec 15, 2017 8:52 am

Hello Sam

can you please be a bit more elaborative on this subject? I saw already few threads on the same issue in last month and I have not seen it at all in the past before I decided to buy the camera. Is it something related to the PRO version (I have one of the very first sold, got it on October 25th during my stay in China)? I have terrible issue for halos around Ha, SII and OIII filters. For LRGB it is so so. but acceptable. I have full ZWO set: 1600MM-C Pro +EFW 7 36mm + ZWo filters.

I saw a proposal to put it further from the sensor, but while reading your marketing you reccomend to put it as close as possible to avoid vignetting... Have you maybe tested this subject with other filters so I would be sure just filters are poor, or is it something that simply diasbles the use of the camera in narreow band?

I saw here people announcing selling the camera already but very few replies from ZWO side. That worries me a lot as the subject seems extrelemy serious and you are known for very rapid involvement in issues solving.

Can you please comment on that subject bit more?
thanks
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L_Ha_2017-11-27_23-38-01_Bin1x1_90s__9C.jpg
L_Ha_2017-12-07_21-28-33.jpg

Ross G
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Re: Diffraction patterns 1600mmpro + ZWOEFW +RGB filters

Post by Ross G » Sun Dec 17, 2017 6:22 am

Sam wrote:this is because sensor is not coated
there is no way to fix this issue
....if you know the issue and you know the issue cannot be fixed, then why are you still selling an astro camera that cannot function properly as an astro camera???....

I also have an ASI 1600MM-C and I have just spent a lot of money on a ZWO filter wheel and ZWO filters.
I have not had a chance to use it yet because of work and weather.
If I see the same problem then I will be returning everything and demanding my money back!

Ross.

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Sam
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Re: Diffraction patterns 1600mmpro + ZWOEFW +RGB filters

Post by Sam » Tue Dec 19, 2017 8:48 am

that's different questions
diffraction caused by sensor or diffraction caused by filter or diffraction caused by internal refection
this is not a problem only ZWO have

there is no way to fix the issue caused by sensor
for filter and optics, you can try exchange the side of filter or filter wheel
so the distance from camera and filter is far
then the reflection would be better
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rockstarbill
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Re: Diffraction patterns 1600mmpro + ZWOEFW +RGB filters

Post by rockstarbill » Wed Dec 20, 2017 12:14 am

Jumping in here...

The first image in the thread shows diffraction caused by the Panasonic sensor in the camera. This is not a ZWO specific issue. Any Astro camera that uses this Panasonic sensor has this problem. It only occurs on really bright stars, and the coating Sam is referring to is Anti Reflective coating (AR coating).

The second post with two images showing a ringing pattern on stars, is related to an issue with the filters in use. I believe ZWO is providing masks that can be placed in the filter wheel to help solve the problem. Also note, the ZWO filters must be installed in the correct orientation. If you have them backwards, you are going to have even more problems. As Sam says, check the orientation of the filters, and you can also move the sensor a little further away from the filter and see what the results are. Definitely get the masks though, as the coating on the filters does not go all the way to the edge.

You do not need good weather to test the filters for this ringing issue. It will show up in flat frames as well.

Kubaman
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Re: Diffraction patterns 1600mmpro + ZWOEFW +RGB filters

Post by Kubaman » Fri Dec 22, 2017 8:10 am

Hi there

my filters are on the proper side of course. The 36mm EFW do not have any holders or fixtures, you just drop the bare filter into the nest and attach by screws with washers. If you look around this forum you'll find out the issue is much more common and some people already sold their cameras due to filter reflection.

The problem is bond in my oppinion as the reflections in the sensor are visible only with specific situation as the filter reflections do. I suspect ZWO/Optolong filters and that's why I asked if ZWO could comment/do the tests with some fine filters for comparison.

I was reccomended ZWO filters so I bought them. I was not aware about the sensor glass reflecting to the filters and back. Now the question is if I should inwest in good filters (not happy of course) or I shoud sell the camera and buy QHY for example.

I redesigned my set up to increase the distance of the filter wheel to the sensor but yet could not tests it due to wheather. But I am pretty sure it'll impact vignetting, and I do not like such perspective. The first of two above pictures is made with 10" Newtonian, second with Canon EF 600 IS L lens. Clearily the issue is between ZWO components - EFW, filters and camera.

rockstarbill
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Re: Diffraction patterns 1600mmpro + ZWOEFW +RGB filters

Post by rockstarbill » Sun Dec 24, 2017 3:34 pm

Kubaman wrote:Hi there

my filters are on the proper side of course. The 36mm EFW do not have any holders or fixtures, you just drop the bare filter into the nest and attach by screws with washers. If you look around this forum you'll find out the issue is much more common and some people already sold their cameras due to filter reflection.

The problem is bond in my oppinion as the reflections in the sensor are visible only with specific situation as the filter reflections do. I suspect ZWO/Optolong filters and that's why I asked if ZWO could comment/do the tests with some fine filters for comparison.

I was reccomended ZWO filters so I bought them. I was not aware about the sensor glass reflecting to the filters and back. Now the question is if I should inwest in good filters (not happy of course) or I shoud sell the camera and buy QHY for example.

I redesigned my set up to increase the distance of the filter wheel to the sensor but yet could not tests it due to wheather. But I am pretty sure it'll impact vignetting, and I do not like such perspective. The first of two above pictures is made with 10" Newtonian, second with Canon EF 600 IS L lens. Clearily the issue is between ZWO components - EFW, filters and camera.
Hello there,

I think you may have misunderstood what I meant. The ZWO filters themselves have a correct orientation. So when you place the 36mm unmounted filter into the carousel, you need to be sure you have them oriented correctly. There is a specific side that should face the camera. This is not the case with other brand filters, such as Astrodon, where both sides of the filter are identical.

The glass on the sensor is not AR coated, and buying the QHY version will not do anything to solve this problem. They use the exact same sensors. In fact, I believe they get their sensors from ZWO anyhow. Regardless, the sensors themselves are not AR coated by Panasonic. Liklewise, buying the ATIK with the same sensor will do no good for this issue. The two problems need to be understood correctly (filters in the wrong orientation/coating issue vs sensor glass reflection).

The images you posted show the problem of either improper filter orientation or the lack of coating to the edge of the filter which causes the ringing pattern you see. This can be solved with masks around the filters, or purchasing different filters (i.e. Baader, Astronomik, Astrodon, etc). There is a lengthy thread on CloudyNights about this specific issue. I strongly suggest you read through it all:

https://www.cloudynights.com/topic/6005 ... artifacts/

The image posted by brandxlb shows the microlens reflection issue caused by bright starts and the missing coating on the sensor glass. This is something that either lower exposures or post-processing can resolve. This is not something anyone is going to solve directly, unless Panasonic starts coating the sensors, and since Astronomy is a low-demand hobby, that is not likely to happen. If your heart is set on the 1600, this is something you will need to live with, no matter which company you buy the camera from.

Kubaman
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Joined: Fri Dec 15, 2017 8:08 am

Re: Diffraction patterns 1600mmpro + ZWOEFW +RGB filters

Post by Kubaman » Mon Dec 25, 2017 8:41 pm

Well, I repeat for the third time. I know what the orientation of ZWO filters is, I read the instruction and YES they are n the proper side from the very beginning. If you suggest one more time I have them on the wrong side I can suspect you're not here to help.. I tested them both sides for comparison as well, as did the other guys who reported in this forum earlier, and the result is pretty bad on each side, cannot really claim the difference in the image.

I am using it exactly as the producer intended and I get bad results. Seems I won't get the answer and I must think over my next decission.

tomt
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Joined: Tue Aug 14, 2018 10:52 pm

Re: Diffraction patterns 1600mmpro + ZWOEFW +RGB filters

Post by tomt » Tue Aug 14, 2018 11:03 pm

I have the same issue. I was very careful to put the filters in the right orientation into the wheel when the camera first arrived.

However I believe I might have put the filter wheel on backwards for the last six months.

I read some instructions today that showed the thick part of the wheel should be facing the scope not the camera.

I will test the results in a few days to see if the halos disappear!

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