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Heavy newton rings with ASI120MM & Quark first light

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#1 arjanb

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Posted 07 April 2020 - 02:46 PM

Just got a Quark chromo, hooked it up to my 120MM with a Zwo Tilt adapter. First light

 

Adjusting the tilt adapter didnt seem to get rid of rings at all. When tilting to maximum, light gets in from the side washing out the image.

Sun_094525_lapl4_ap1865_conv.jpg

 

While waiting for a 102/F9 scope to arrive, i put it on my WO GT71 at F5.9.  Image of the train here as well:

TrainAnnotated.jpg   (oh yeah, UV/IR cut 2" filter before Quark 2", not before Diagonal)

 

Any tips to optimize this? I did order a ASI174mm since generally people say the global shutter solves a lot of this.

 

i hacked two images together really quick (have mercy with my beginner status) and it's not super terrible but the rings are nasty) 

fasthack.jpg

 

thanks all


Edited by arjanb, 07 April 2020 - 03:01 PM.

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#2 MalVeauX

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Posted 07 April 2020 - 02:52 PM

Heya,

 

That's a lot of weight/torque/moment arm on your focuser, while it may be a good visual focuser and ok for light train imaging, clearly it allows a lot of tilt with such a big load on there. It may take significant tilting to handle it.

 

To better assess the tilt, go to the center of the disc approximately and defocus so you don't see any detail. You'll still see newtonian rings but this way that's all you see. To make them even more obvious, crank gamma so that it results in a high contrast, dark image, with very easily visible newtonian rings. Unscrew the bolts on your tilt adapter as far as possible, and go through all the angles of your camera onto that tilt adapter and watch the rings change as you move. When they're the least obvious, that's where you want to position things, then gently tighten it up and adjust real time to keep the rings as suppressed as possible. Turn gamma back off when you're done (or neutral). To further eliminate the rings, now do a flat calibration frame, as in, a defocused image at around 67% histogram fill and apply it real time (FireCapture) or in post (SharpCap).

 

Very best,


Edited by MalVeauX, 07 April 2020 - 02:52 PM.

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#3 arjanb

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Posted 07 April 2020 - 03:13 PM

Marty, many thanks for the reply, your images are certainly a big inspiration for me!

 

Very helpful instructions, I'll give that a try that when it's clear again.   It sure currently has a lot of torque, had to put a drop of Loctite on the scope adapter to keep it in place...

 

Would you say it's better to just go straight out of the scope without a diagonal? your scope's trains look very long with a couple of 85mm extenders. 

 

I have a SW100ED F/9 coming, but that focuser might be worse then the GT71. Perhaps i should get a decent GSO linear bearing crayford focuser for that one immediately as well?



#4 MalVeauX

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Posted 07 April 2020 - 03:30 PM

Marty, many thanks for the reply, your images are certainly a big inspiration for me!

 

Very helpful instructions, I'll give that a try that when it's clear again.   It sure currently has a lot of torque, had to put a drop of Loctite on the scope adapter to keep it in place...

 

Would you say it's better to just go straight out of the scope without a diagonal? your scope's trains look very long with a couple of 85mm extenders. 

 

I have a SW100ED F/9 coming, but that focuser might be worse then the GT71. Perhaps i should get a decent GSO linear bearing crayford focuser for that one immediately as well?

Heya,

 

I use straight through image trains for imaging because (1) it takes the sunlight off the filters, (2) the weight in the same space is spread out, (3) the moment arm is a bit more, but, I can deal with it with better focusers (4) I use linear bearing class crayfords that can handle 9lbs, so I have very little tilt to begin with. I don't even use tilt adapters these days at all. You can solve most of your issues with rigid gear and higher quality linear bearing or superior focusers that don't allow slop with significant load. Diagonals allow some play, in my experience, and the weight distribution relative to the 90 degree angle makes for minute shifts in tilt that are not needed. Plus the mirror in the diagonal is robbing you of another 1% or less transmission, plus adding yet another surface with dust and imperfections to deal with. I put no value on diagonals for imaging; just visual. I'd rather use straight through with less glass and no angles to deal with other than straight. Also, because the extensions are extending out of the scope, the scope's focuser stalk is barely out of the focuser, further making it rigid and keeping it very straight.

 

Very best,


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#5 IR656nm

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Posted 03 May 2020 - 01:22 PM

Hello,

 

Have you had any success with eliminating Newton rings yet? 

I also have a ZWO 120mm-S with a Quark, I tried a ZWO tilt adaptor, but that does not work, Someone said you need longer screws to increase the angle (about 2mm separation or more), but I think the resulting image blurring may be a problem. 

 

Daystar have a another type of tilt adaptor called an interference...device. 

 

Anyway, using flats seems to partially remove it, I am finding out why its doe not always work. Maybe because of drifting of the Newton rings with movement of the sun across the camera sensor. Also, the level of your flats may be a factor. 

 

There are other things to consider, but I am in process of converting to a straight through imaging train like MalveauX. 

 

My ASI120mm-S images are getting better. I also use solarchatforum.com as Boso36

 

Maybe you can get advice there.

 

IR656nm

London

 


Edited by IR656nm, 03 May 2020 - 01:23 PM.


#6 arjanb

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Posted 03 May 2020 - 02:52 PM

i bought a 174, a upgraded GSO focuser and other things.  Get as much of the image train straight, then the final part is the Camera itself. The offset with the Tilt adapter can be pretty high, best way i found is to loosen the tilt adapter and manually moe it around until minimum rings.  Then, Flat do the rest

 

I'm getting better. this was a process of yesterday

Sun_050220_IG_compressed.jpg


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#7 Gray

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Posted 05 May 2020 - 09:18 PM

Man I'm glad you guys addressed this issue.  I am going through the same problem.  Gonna see if I can make a straight through imaging adapter out of the a spare blocking filter and then use the Telescope (sp) express tilter I got.  Thanks Marty!  Did not know you could add a flat in FC for real time.  That's cool.


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#8 IR656nm

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Posted 08 May 2020 - 01:35 AM

i bought a 174, a upgraded GSO focuser and other things.  Get as much of the image train straight, then the final part is the Camera itself. The offset with the Tilt adapter can be pretty high, best way i found is to loosen the tilt adapter and manually moe it around until minimum rings.  Then, Flat do the rest

 

I'm getting better. this was a process of yesterday

attachicon.gifSun_050220_IG_compressed.jpg

Hi Arjanb,

Was this image with asi174 or asi120mm-s camera? It was not clear. Is the asi174mm still give newton rings with a quark?

Did you find the degree of separation of the tilt adaptor? Was the orientation of this tilt dependent on the camera sensor position relative to the tilt? 

 

 

By the way, I found a way to remove newton rings, using a Fast fourier transform process, as described by a forum post by jbalsam. 

 

Very best,

IR656nm



#9 arjanb

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Posted 08 May 2020 - 09:35 AM

Sorry for not being clear: last image was with ASI174MM. No issues with that, if they happen it’s something off in the image train (like my new focuser was not entirely straight inserted). So what I’ve read is that the 174 has a Global Shutter , with which the entire frame is read out at once which gets rid of the interference patterns. https://thinklucid.c...s/sony-pregius/

Finding how much tilt was needed in cases, I haven’t done much investigation but you can basically loosen that Zwo adapter and move the tilt plane around in a 360’ circle while watching the live view. Fixate it while you see minimal rings. That worked for me easily. And the tilt plane/angle in my case was fixed to camera orientation, but this will not be true if something else in your image train is off.

Cheers
-arjan

#10 ASTROTRUCK

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Posted 10 May 2020 - 10:44 AM

for those of you with the external etelons there is the diagonal with the needed filter resulting in the need for the diagonal either viewing or photographing. add the powermate & rings seem to be a must by the newton ring gods. flats never seem to work with me cant figure out firecapture artificial flats.

 

anyways my next time around i shall take up tiddlywinks as a hobby

 

ps   - -  virus days   --  i guess every one has noticed with far fewer cars on the road & fewer people out there ,  there are many more clear blue sky days for solar   --  not that i wish this to continue but ... it does prove that cars & buses cause very major pollution




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