Sun H-Alpha 14.03.16

[Macavity]

Another early start (gasp)! First, I thought I would revisit this 
brightness asymmetry in my images. Found to my surprise that,
via a further rotation of the diagonal about the axis (clocking), I
I could actually *center* the sweet spot within the solar disk!

The immediate effect was that the image was a lot smoother,
but, the previous Newtons Rings seemed more distracting?
Anyway, finally worked out a way to combine disks & proms
(Nowhere as good as the experts - Still on learning curve).

This from about 11 a.m. this morning:

I decided I'd have to bite the bullet and TRY the idea of turning off
the tracking during the exposure (Had to go from 1 min to 30sec).
At first I was circumspect - My carefully centered sweet spot clearly
would NOT remain *central* throughout the exposure now ...

But this from about 2.30 p.m.

HEY, it really worked! Gone are the pesky Newton's Rings! 
Not so easy to remember to DO all these things but...

[laudropb]

Very nice image. Spectacular looking prom and no NR. Well done.

[Macavity]

I think there is a slight loss of contrast from the (removed) Newtons Rings.
If I can think of a way that doesn't completely STOP the telescope too?

I was struggling a bit with colouring the images via HSV, but discovered
the section, from Michael's guide, on using curves in GIMP RGB channels:

As (someone) predicted, this exposes a slight "white lie" about the Sweet Spot being
*absolutely* central, but I sense with a bit more tweaking (in hardware or software)

For this and more, my thanks... and a (manly):

P.S. The purists may note the "offset circles" around the image? I suspect these are
symptomatic of the slightly tilted optical axis? If fairness, I *overcooked* the proms
in my desire to reveal the fainter ones. Or maybe a guide to precise adjustment?

[Montana]

Wow! the second image is a stunner

Alexandra

[Davey-T]

Looking good Chris, don't know why Newton invented those damn rings, they're neither use nor ornament

Dave

[Lowjiber]

Wow Chris!  That is very nice work on both the proms and the disk.

Congratulations on getting those NRs under control... excellent detective work.:)

If Gimp will allow you to re-size the image, try shrinking the prom disk 1-2% before fitting the surface to eliminate that small ring.:)

Clear Skies

[Pete Presland]

Interesting experiment,  looks like the Newton rings have been banished! I have never tried rotating the diagonal before, another thing on the "to do" list!

[David Smith]

Good job getting rid of the newton rings, love the colour image!

[skybadger]

You use a diagonal ? Why?  Doesn't it add a big chunk of leverage to the focuser ? Maybe that's why your NR went. Just interested. I tried my quark with and without diagonal and it gets you out of staring the sun in the face for visual but I wouldn't hang a camera off the diagonal if I could help it.

Cheers

Mike

[Macavity]

Heheh. No other choice? The essential blocking filters are integral
to the scope diagonal. I sense most imagers wouldn't chose to do
so via a diagonal, but there is no (inexpensive) alternative.  

http://luntsolarsystems.com/product/lunt-blocking-filters/

Rather limits the flexibility (in-focus etc.) re. use of Barlow lenses
too. But I'm philosophical? Solar scopes are pretty "leading edge"
for something readily available for the amateur market? 

The Newton's Rings are likely generated between the CCD and the
cover plate by cameras which (in all fairness) were never designed
for use with a narrow band monochromatic source...

[Macavity]

For interest, I recorded the solar image taken with the diagonal
clamped firmly within the holder at ~90 deg intervals. Recently,
I was at the "Up" position, but improved things to be as "Left".
Of course, randomly, I started out at one of the other two... 

The results are not "orthogonal". I presume because of the vagaries
of the diagonal, the focuser, integral brass ring clamping system etc. 
I do intend to try a direct T2 screw connection sometime...

[Macavity]

The keen eyed may have spotted the image and text didn't correspond?

Thanks for the "like", Lowjiber. I think there is still room for your (Earl's)
methodology of "crescent reduction"... PM / Email received - My Thanks!