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ZWO ASI174MM bands on image - normal or a problem?


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I don't know if this is normal for this camera or whether it is something that shouldn't happen.

I get these alternate dark and light bands across an image. If the camera is rotated the bands stay put. implying they are caused by the camera. I tried white light just pointing the scope at the clouds and on all levels of brightness there was no sign of the bands. Newton's rings are also present but I understand those. Whatever the cause, they are removed with flats but I would rather they were absent for those occasions when the clouds don't permit the taking of flats.

Has anyone the same experience or do you think I should contact the camera supplier.

I wondered if it was an interference effect caused by two surfaces in the camera which only show in monochromatic light.

The picture show the same image with and without flats applied.

AR2371bands1.jpg

They are even more noticeable if the full sensor is used. This was a ROI.

Dave

Edited by Dave Smith
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Thanks James. I also wonder that but you will see in my image above, especially bottom left and also top middle and right, the more normal finer Newton's rings. What I am a little concerned about is the much broader horizontal bands which could be caused by two almost parallel surfaces, the same principle as Newton's rings except they are caused by spherical surfaces as in a lens.

I was just hoping someone would recognise it as a totally different cause.

Dave

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Yes....I get them too (Altair triplet and Quark).

Getting the imaging train as solid as possible (screwed connection to camera, self centering "twistlock" extension tubes) all help. Good flat fields in AS!2 will correct for anything that's left.

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Hi Dave,

I use the ASI174mm and don't see these effects at all although I do apply some tilt to the camera as there are some faint Newton rings without tilt. Just wondering if you have tried tilting your camera to see if it has any effect on these wider bands?

Pete

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Hi Dave,

I use the ASI174mm and don't see these effects at all although I do apply some tilt to the camera as there are some faint Newton rings without tilt. Just wondering if you have tried tilting your camera to see if it has any effect on these wider bands?

Pete

Thanks for that Pete. I have tried pushing the camera to one side with no effect but there isn't much room for movement as it is all fairly well clamped. How do you do the tilting?

Dave

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Thanks for that Pete. I have tried pushing the camera to one side with no effect but there isn't much room for movement as it is all fairly well clamped. How do you do the tilting?

Dave

Hi Dave,

You can purchase a tilting device specially made for this purpose. I got mine from Telescope Service but other suppliers probably do them as well. Have a look at their website for details.

Pete

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Thanks again Pete. I did wonder if you meant one of those. At the next opportunity I will try loosening things and see if tilting works before spending any more. One problem with this hobby is that spending never seems to stop !!!

Dave

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Thanks again Pete. I did wonder if you meant one of those. At the next opportunity I will try loosening things and see if tilting works before spending any more. One problem with this hobby is that spending never seems to stop !!!

Dave

Yes, best to verify if tilting the camera cures the problem before shelling out any cash. As David mentions I would have a look at DIY options also. Totally agree about the seemingly never ending costs though!!

Pete

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I'm going the other way...Im trying to get a fully screwed connection from my focuser to the Quark to the camera. I'm a bit wary of tilting anything in case parts of the field end up out of focus?

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Hi Dave, do you still get the same problem using a focal reducer ? I get Newton rings which disappear if I use the .5X focal reducer.

Dave

If anything it is worse which is why so far, since getting the ZWO camera, I have only done images without FR. The amount of Sun in the last few days has been minimal (I was away at the weekend) so haven't been able to experiment properly but it would seem that a 2" 0.5x FR between the camera and Quark causes heavy vignetting even though the connections are 2" but a 1.25" 0.5x FR screwed into the front of the Quark does much better. Also it surprisingly doesn't seem to be getting hot.

I am borrowing a tilt adapter in order to experiment but could really do with a nice clear day without clouds.

Dave

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  • 7 months later...

I also had this same issue. I have a Lunt 80mm Ha scope single stack, ASI174MM cam, 2.5x Power mate and 2x Celestron Barlow both gave me banding it was suggested I try a Teleskop Service T2 Tilt Adjuster but all it did was frustrate me. The camera body blocked the adjustment screws and I had to remove it for each adjustment by which time thanks to my PTSD and short term memory issues I would forget which screw I adjusted or which direction. It was a pain and I NEVER got it to work.

 

sunNR4

 

 

 

sunNR1

 

sunNR2

 

sunNR3

 

A few days ago I had posted some images on Solar activity Newton rings and all and someone messaged me with suggestions on possible fixes most of which I had already tried. I mentioned my desire to buy a 152mm doublet and Daystar Quark but till I fond out how to remove the rings I would not be able to. Little did I know the person I was speaking to was Jen Winter The owner of Daystar. She suggested I try a product they carried and though skeptical I agreed.

The product was a Moonglow Technologies Interference Eliminator.   and much to my amazement it worked! It arrived a few days ago and even though the seeing was 1/5 and rotten I just had to try it out. Please keep in mind I did a fast setup and seeing was so poor focus is not perfect and did not clean my optics first. What I wish for you to focus on are the Newton's Rings. Once the Interference Eliminator is attached it does not need to be removed to make adjustments just loosen 2 medium sized thumb screws make adjustment and tighten back down take your image again and adjust as needed. I did a full disk of the Sun keeping the best 25% of 1000 frames without and with the Interference Eliminator and a close up of Sunspots 2490 & 2493 25% of 3000 frames with the device. Sadly the Sun went down before I could do a fine tweak of the Interference Eliminator as I still have fine rings visible that I believe with minor adjustments can be removed, but I am still amazed at the results. Let me know what you all think.  I am pleased with the results even though not perfect are a LOT beter than my previous efforts.

 

url], on FlickrAGAIN do not dwell on the image quality or the focus this is just to show before and after use of the Interference Eliminator, I am as amateur an Astronomer as they come and this was straight forward and easy for me to use.

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As Davey-T has said this is an interesting if somewhat expensive solution to Newton's rings.

 

I have found that a Rowan Tilt Adapter works brilliantly on eliminating Newton's rings and is much cheaper.

Tilt-adapter.jpg

Unlike the tilt correctors already mentioned this is designed to eliminate Newton's rings rather than correct for tilt in the image plane. Since using it I no longer get any broad banding or finer Newton rings.

 

Dave

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