Large dark area on Sun in H-alpha

[Rusted]

Hi Guys,

Continuous sunshine this morning at 55N.  Blank in white light.

Large, dark area in H-a is only now showing on GONG [Cerro Telolo] but with a different perspective.

I can only see it if I lift the sagging binoviewer. Need some extra support for proper alignment to bring out the surface features! Sky hooks?

The Sun's limb is 'boiling' as it scrapes along very low down. No prominences visible from here.

Chris

[Peter Drew]

You could try retuning the PST etalon to bring out different details in the dark filament. If the filament doesn't lift off before it reaches the limb, it should provide a significant prominence. Foggy here!    ?

[Rusted]

Hi Peter,

I've now found a triple chimney stack prominence.

I'm not sure whether it is the etalon but I get a dark "doughnut" at best focus on surface texture.

I've been trying to capture the effect with my compact camera. The image attached is quite an exaggeration.

The real view is much more subtle and exposes better surface detail in the ring as I move it about.

The dark area is still there as a gently curved, broad line and is in my north of the Sun's disk. So probably true south.

[Rusted]

Now I have a very dark spot right of center on the disk so probably true left. [East.]

I'm using the T-E binoviewer direct view with 32, 26 & 20mm in H-alpha. 41x-65x. No GPC.

No sign of any surface detail in the 7" in white light at powers up to 110x.

Tried various filters including the green Solar Continuum without luck.

[Peter Drew]

I can't remember the optical train that you finally decided on, if you still use the original ITF that was placed forward of the blocking filter, it would be worth checking for any degradation. PST etalons are not all equal and display many different artifacts whilst tuning, my current one is the best out of many. Despite the high magnification I find the entire image to be much more evenly presented when using a binoviewer with just the 2x Barlow lens cell screwed to the nosepiece of the binoviewer. This arrangement seems to offer a similar apparent field of view to that of a BF15 blocking filter and at a fraction of the price.    ?

[Rusted]

Hi Peter,

I'm using an old fixed cell,  CR150HD with internal 90mm D-ERF, a new Mair ITF, PTSD! internals of Etalon and BF.
I turned a 2" adapter to 36mm bore to take the PST's eyepiece barrel, BF and etalon assembly.
I really ought to add a compression band to tighten this up.
The sag with the weight of the binov. + 2 low power EPs spoils the alignment.

I haven't been using a Barlow. Though I do have the two different T-E GPCs. 1.8x and 2.8x.
I find the power's far too high to be useful even with 32mm EPs.

I tend to get the clearest surface detail around the edges of the disk.
Then the darker "do-nut" of increased contrast at about 2/3rds diameter. 
The center of the disk is the last bit to show any surface detail.

Proms and surface detail tend to be at the same tuning.
I am constantly re-tuning and refocusing to find the best views.

 

[Pete Presland]

A couple of nice proms and a filament still showing on GONG.

[Alan White]

Can someone please tell me what GONG is other than a large brass thing you hit with a stick!

[Stu]

6 minutes ago, Alan White said:

Can someone please tell me what GONG is other than a large brass thing you hit with a stick!

Here you go, Ha Observatory data online

http://halpha.nso.edu

[Alan White]

Aha, thanks Stu.

GONG = Global Oscillation Network Group

[Rusted]

A pregnant, male gong basher? Surely not? ?