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Solar - With some tilt

Freddie

By Freddie
in Imaging - Solar

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Freddie

Freddie

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post-7987-0-84516500-1439227580.png  post-7987-0-61772200-1439227546.png

Both these were taken with my new tilt adaptor as supplied by Rowan Astro (1parsec on SGL)

Newt rings were always an issue with the Quark and ASI120m and what I found a pain was that flats would only solve the problem 75% of the time. Some rough and ready maths showed that with a 6 deg tilt the chip would still all be within critical focus so the adaptor was fitted. Has some very nice features to keep stray light out, allow you to align the direction of tilt with the chip and allow fine control of the amount of tilt. A comparison to "no tilt" shots has shown there is no adverse impact on image quality.

Very useful, it will be staying on my set-up permanently as rings are now a thing of the past!!!

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Freddie

Freddie

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Thanks for the comments guys. The adaptor has made things easier with focusing as there are no dark lines to confuse things though I always did manage to get spot on focus, it's just easier now.

Michael, like me I think you would find this a useful addition to your kit.

Dave, on the odd occasion I used a FR the rings were significantly reduced so I think I wasn't a lot different to you in that regard.

Craig, it was ~£50 and well worth every penny for me as there was nothing worse than completing an imaging session and then finding none of the 4-5 flats worked properly.

Can be purchased from here

http://www.rowanastronomy.com/index.htm

Other tilt adaptors are available but the issue often is that there isn't enough tilt in the available adjustment to completely get rid of the rings.

I'm very pleased with mine and it has definitely completely solved a problem I had.

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Freddie

Freddie

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Helen, it certainly solved my problem so it's probably well worth a look.

Pete, yes the 1.25" screws into one side of the adaptor and the other screws direct into the ASI. I haven't yet bothered with the adaptor which lets you screw direct to the quark as I wanted to check I had enough focus travel first.

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Ewan

Ewan

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It's nice things are working out for you Freddie regarding the NR's, it seems the ASI ccd's seem to suffer a fair bit with this, the one thing that's put me off buying one.

Nice images as well.

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Freddie

Freddie

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Thanks Luke.

Definitely agree it's best not to have to solve a problem that could be avoided. I wonder if ZWO are looking into this as I believe many of their cams suffer from rings when IS cams (and maybe others but I only have a DMK to compare to) don't.

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Helen

Helen

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Adapter arrived  :grin: Sun shone  :grin: (ok between clouds  :rolleyes: ) adapter cured newton's rings  :grin:  :grin:  :grin:   I need more time to try to get the minimum tilt required to remove the rings while keeping focus and illumination as even as possible, but a result!

Helen

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Freddie

Freddie

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Glad you have the rings problem sorted Helen. Yes a bit of time for fine tuning to only just remove the rings is well worth it. It is also worth aligning the tilt to the shortest dimension on the chip to minimise the potential difference in focus across the chip.

I initially got a bit carried away concentrating on adjusting the tilt and ended up not being able to pull the two halves together fully. It's worth checking that and just back off the two tilt adjusters the same distance to enable to fully close the two halves. It has all the adjusters necessary so all this is easy enough done.

All I need now is more sun and fewer clouds !!!!!

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Ewan

Ewan

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Thanks Luke.

Definitely agree it's best not to have to solve a problem that could be avoided. I wonder if ZWO are looking into this as I believe many of their cams suffer from rings when IS cams (and maybe others but I only have a DMK to compare to) don't.

Me too Freddie, I am waiting to see how my DMK618 does with the 152mm when it arrives & then decide if I need to upgrade & what to.

I cannot decide if it's the ZWO ccd's as a whole or just the sensors used, I know I need to look into it & as you say to start with no NR's in the first place is better but glad you got it sorted.

I am already looking at a PG ccd just depends on how much it will set me back, astro fund needs topping up...............as always.

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JamesF

JamesF

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My understanding of the problem is that it is specific to the sensor and that there may be at least two contributory factors.

The rings are an interference effect caused by light reflecting off surfaces that aren't perfectly parallel (and we're probably talking about parallel to within fractions of a wavelength of light).  In this instance I think that's probably the covering of the CMOS sensor itself.  I feel sure I saw them before I added the optical window to my ASI120MM (mine is one of the early ones that doesn't have an optical window), so I don't think the optical window is the cause.

I've also read that there may be some way in which a sensor using a rolling shutter exacerbates the effect though I can't claim to understand why.  I believe the ASI174MM, which uses a global shutter doesn't have problems with Newton's Rings, though perhaps that could also be because it is more accurately manufactured.

My recollection is that the ASI120MM and QHY5L-II both use the same sensor and both show Newton's Rings.

I'm not entirely sure why tilting the sensor works as a solution, though perhaps if you tilt the sensor the reflected light has to travel further inside the sensor cover (because it's now at an angle) and at the correct angle that additional distance means it ends up in phase with the unreflected light.

James

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Dave Smith

Dave Smith

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Very interesting Freddie. I have received my tilt adapter from RowanAstronomy and am eager to try it out. Dave (1parsec) very kindly loaned me the prototype version of the adapter and that certainly solved my NR problems. What with holiday and visitors I haven't been able to try the production version out yet. It certainly seems well made. Today has been ultra gloomy but hopefully there will be some Sun soon. What angle have you found works for you? With the prototype about 3 degrees seemed the minimum angle for me.

Dave

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  • 3 weeks later...
gnomus

gnomus

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Very interesting Freddie. I have received my tilt adapter from RowanAstronomy and am eager to try it out. Dave (1parsec) very kindly loaned me the prototype version of the adapter and that certainly solved my NR problems. What with holiday and visitors I haven't been able to try the production version out yet. It certainly seems well made. Today has been ultra gloomy but hopefully there will be some Sun soon. What angle have you found works for you? With the prototype about 3 degrees seemed the minimum angle for me.

Dave

How are you guys measuring the angle of tilt.  My Rowan Engineering tilt adapter came a few days back, but today was the first day I got to use it.  The Newton's Rings have completely gone, but I have overdone the adjustment and only about a third of the image is in acceptable focus.  I will try backing it off a bit.

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