The dreaded rings

[valleyman]

Gone back to Solar imaging after a long lay off, and have been out the last couple of days at last as the weather turns decent at last.

Taken a bit of time tuning the mount and Scope to speed up the start up time but now it is all up and running I.m getting the dreaded Rings on the images.

Any advice would be appreciated.

The kit is a Williams 81m APO with a Quark and 120 mini Camera .

regards

Pat

[Rusted]

The usual advice is to use a tilt plate on the camera adapter.

ZWO T2 Camera Tilt Adjuster II | First Light Optics

[valleyman]

1 hour ago, Rusted said:

The usual advice is to use a tilt plate on the camera adapter.

ZWO T2 Camera Tilt Adjuster II | First Light Optics

Thanks Rusted will give it a try, was wondering what next to spend even more money :).

I see you are from Denmark. I did some sailing there during the 70,s and 80,s out of Kiel round the Islands. Sonderburg, Faaborg, Aero, and round Fyn. Learnt my sailing there and ended up as a Instructor with the Army.

Had some fantastic memories round there and just loved the country and People. Envey you mate. 

[Rusted]

If you want to spend more money there are upmarket tilters.

Thanks. I am in exile, rather than a native, but agree on the countryside.
It is very peaceful in comparison with anywhere in Gravely Blighted.

[tooth_dr]

I’m not sure if you will have the same experience as I did, but I couldn’t resolve NRs completely with my 120MM mini with the above tilter. 

[valleyman]

On 15/07/2021 at 18:18, tooth_dr said:

I’m not sure if you will have the same experience as I did, but I couldn’t resolve NRs completely with my 120MM mini with the above tilter. 

Thanks for the heads up tooth. Will have a try with My ZWO 183MC before spending any more money.

Dog just cost me £340 at the Vet and then the cooker just packed up grrrrr another £500.

Pat 

 

[Rusted]

Newton's rings may be caused by the position of other components and their distance relative to the camera .
I don't have any filters on the camera's T2-1.25 nose. These would place plane-parallel surfaces very close to the camera.
I do fit GPCs on the camera nose, as weak Barlows, but these don't have flat surfaces.

Monochromatic light, like H-alpha, brings out the worst of Newton's Rings when they are undesirable.
Such light is used for testing optical surfaces in contact. You can get the same effect with fluorescent light, but weaker.
I used to carry my [8.75"] optical flats across the road to a [mono] street lamp to check figuring progress.
Then I found a yellow,  low pressure, mercury vapour lamp in the bin at work.

[Merlin66]

The NR we see in solar observing, are only really noticeable in Ha.

A double stack configuration with very narrow bandwidths (<0.5A) and the use of barlows/ powermates etc aggravate the situation.

The NR interference is an artefact caused by the spacing between the coverplate and the underlying silicon chip in the camera. The thickness of the coverplate (usually around 0.8 to 1.0mm) can also play a part. 
These variables mean that some cameras are more prone to developing NR than others.

By changing the effective thickness of the coverplate and the gap below, it is possible to suppress the NR, hence the success of the T2 tilters. Weak wedge prisms mounted directly on the chip coverplate have also been used, but not recommended to the solar imaging amateur.

If all else fails, then flats can be used to suppress the NR. Easier to apply to surface images than full disk images.

 

[Chris-h]

You can get rid of NR in Photoshop with a plugin called 'Fixel FFT Wizard 2' (I had to use V1, V2 never worked for me). Works great if you only have a couple of images to process.

[Merlin66]

Chris,

That and some other programs can handle NR when they are seen in a whole surface image.

They don’t work with full disk images.

 

[Chris-h]

Did for me. Well ok, 98%. I had to feather out the edge of the sun due to some artifacts from the process.