Solar Activity 27th Aug 2020

[Merlin66]

SpaceWeatherLive shows no AR or spots visible.
However there's a disturbed area in the NW.
A couple of small but bright proms.
Lost a few images due to cloud....
Enjoy.

[PeterM]

Nice images Ken, thanks for sharing. That 3rd one with the prom is superb!

[Merlin66]

Peter,
Thanks!
I need to find a solution to the NR with the double stack set up.
The tilter is at max and still NR....
I'll try different orientions of the camera to the etalon tilt axis.
They seem to be there with all my barlows (PM, Baader, AE and the ES)

[PeterM]

Hi Ken,
Ok I see the rings now in your prom images but I didn't notice until you mentioned. So didn't/doesn't detract from the images for me.

I am coming from little experience here but am sure I will be going there so have been reading about the dreaded NR and found this article. You have probably seen it and you have already tried the tilter but seems some other thoughts in there also.
Also found the attached camera guide for Solar Scopes - seems some are more NR affected than others? Why is this? Says my ZWO120MM should be cursed by NR but I either don't know what I am missing or lucky.

https://brierleyhillsolar.blogspot.com/2016/11/a-review-of-solutions-to-newtons-rings.html

[Merlin66]

Peter,
Mark is active on the Solar Chat site and his results mirror what others have concluded.
The first line of attack is definitely the tilter - this changes the effective thickness of the chip cover plate and tends to suppress the NR. The optical wedge has the same effect.

NR are definitely aggravated by the use of barlows etc.
The tests this morning - rotating the axis of the blocking filter - no significant improvement.
Increasing (further - longer screws fitted) the tilt does suppress the NR.
I conclude that the tilt axis should be aligned with the height of the chip, this seems to give repeatable results - maybe with slightly reduced tilt
Onwards and Upwards.
( The ambient temperature/ camera temp and seeing conditions can also affect NR)