Sun H-Alpha 10.03.16

[Macavity]

Replaced ASI 120MC (color) by ASI 120MM (mono) camera and produced
<drumroll> Newtons Rings? Feeling a bit deflated now, if truth be told...

Still not processing savvy. But were the whole image like the BEST bits?  

  

I did wonder if my "patent method" for improving ALL (lol) astro images would work... What do you think?

It rather loses the nice 3-D effect. Maybe has more detail? Anyone think the banding is reduced?

The hardware solutions intrigue, but not sure I have the "gastric fortitude" (funds) for experiment.

[xtreemchaos]

 great images Chris, the 2nd one is more contrasty to my eyes but hard to pick a fav,thay both look good. new AR coming round nicely.thanks for sharing  charl.

[michael.h.f.wilkinson]

Actually I had MUCH worse Newton rings with my old ASI130MM. These are not too bad. There are various ways of combating Newton rings. The simplest technique I have used is to let the image drift a touch over the chip. Stacking then cancels them out, provided the rings are not so intrusive that the stacking software sees  them as features. One other method is with flats. I put a few layers of cling film over the scope (not touching the optics, of course)  to create a flat frame which should only contain the rings, and any dust bunnies.

[Montana]

I prefer the first image, I think the second has more pronounced NRs? still a fabulous shot though. Try tilting the camera a little or a flat field 

Alexandra

[Lowjiber]

Very nice images, Chris.  The NRs are a bane of the ASI 120MM.  I've found that a bit of tilt works fairly well, but have also used the drift-across-the-chip method described above.

One thing I noticed is that the tuner is slightly off-band, causing the crescent-shaped east part of the disk to be brighter that the rest of the surface.  It looks okay, but when you start to add false color it will be even more evident.

I took the liberty of copying your sharpened disk into Photoshop and bringing the brighter crescent closer to the rest of the disk.  It's not perfect, as I had to use a JPEG.  However, with a TIFF the process is so foolproof that even I can do it.

I didn't "invent" the method, as it was taught to me by John Earl from Australia, who is a master of the craft.  If you're interested, send me a PM with your email address, and I'll pass it along.

Respectfully and Clear Skies

PS:  I'll note also that if you do the darkening method above before you sharpen the original disk, the features will pop-out more in the area than shown below.

[Macavity]

Thank you ALL for your thoughts and encouragement... and (most recently) Lowjiber.

I was up with the Sun this morning! I am normally a Video astronomer, so the mount
is operated remotely from my own "stargazer lounge" desktop - But hardly conducive
to precise control of the image position within a frame  -- Very frustrating yesterday!
But via a spare cable & "Teamviewer" I can now be NEXT to the mount / laptop.

Anyway, I am now able to "move the sun" closer to where the tuning might be more
uniform. A "crescent" still remains, but it is (hopefully) rather smaller and at the top!
But I would be really interested to try to improve it further... Will indeed PM you LJ.

I think I am a little LESS worried by the NRs now. I tried making a few artificial flats
(from the .tif image) and there was an improvement. So they may be manageable?
Some thin high cloud persisted throughout the session, but that was but a minor
issue! I even took a few white light images with my (too little used) ED-66 APO...

Once again, thanks everyone.  I'm going to really enjoy the odd "solar day" now!
I will put the images up "properly" - Alongside the other ones I so often admire. 

P.S. These ones are just for those who appreciate "organised chaos" (+ clingfilm)?

[Macavity]

No "rocket science" from a novice, but thinking a bit more about it, there are TWO issues?
One is the Newtons Rings, the other is positioning the "sweet spot". Reading around a bit,
I found that to defeat NRs by tilting required (in one case) a custom "tilter" of 5mm tilt! 

Personally, I have found that rotating and firmly clamping (M4 bolt!) the diagonal worked
re. the sweet spot. At least (fortuitously) I have this square to the RHS of the rectangular
field where the tuning is more even? I now have a T2 Rotator and sundry T2 adapters to
play with. I'm never too happy with brass rings - I may try directly attaching the diagonal!

For my own interest (or anyone still here) I did try a quick "cling film flat field". The IMAGE
(as processed by me) was not a complete success (lol). But the flat certainly shows NRs!
And I sense at my level (or where a barlow-ed sun covers the whole chip) it could be useful.

The raw image was more elliptical - Maybe I should buy Waitrose not Tesco clingfilm? lol
I have a DIY MDF ring over which I can test various materials (e.g. solar film) - I may try
a few other random almost-transparent materials. As a Video Astronomer, using cameras
that often get quite HOT, I often have to "scale" any darks or flats before processing...

[Pete Presland]

Some good detail despite those rings!