First light with Double Stack
My target has been to be able to capture prominences and the solar surface with a single exposure. As you will have seen from my previous images, it is possible, but at the expense of a lot of work, strong stretches, and in the end, the contrast that is possible is limited. Looking to double stack (DS), it appears that Lunt 60 DS unit is not currently available?  But I was surprised to see, at half the cost, the Lunt 50 DS unit works well with the Lunt 60, no adapter required. Not being the most patient person, I opted for the Lunt 50 DS unit. And I know now my seeing is rarely great, so I would loose nothing in going to a slightly smaller aperture.

I am blown away by the difference in contrast. I have loaded images to show both the SS and DS under nearly identical processing. I used the double stack stretch for both, to show how bland the single stack is without extreme processing.

Seeing was average for these images, so that was okay, but it was too windy and there were clouds passing through, which is causing the changes in brightness across the image. I'm glad I went out despite marginal conditions, it was more than enough to show the improvement.

My only issue was the reflection of the Sun to the left. I somehow manage to subdue it, but I need to find a better solution. It is a known problem with double stack, hopefully I can manage to move the reflection a bit more to make processing easier.

About the image
There was not a huge change in the prominences or the surface in general in this hour of imaging. But there are some interesting things going on with the prominences/filaments, so please look around the Solar animation in full resolution. That being said, it seems to me the Sun is a little less active most recently, I hope this doesn't mean that our solar activity has peaked early. I have my fingers crossed that activity will pick up again.

Capture and Animation Steps
My animation used brightness inversion on the solar disk, thus both prominences on the limb and surface (the latter are called filaments) will appear bright, as will surface sunspots. Seeing was just average and there was variable haze/transparency during the capture. But I learn something every time I image, so this is another learning experience.

This video of 33 frames was created from images taken on October 28th over  65 minutes. The individual frames of the animation were all from 60 second SER videos at 2600x2600 pixels in 16 bit mono (the camera is 14 bit) taken at 24  fps. Each video was separated by a delay of 60 seconds. The resulting 1350 frames were stacked in Autostakkert3 as the best 15%, so about 270 frames were used in each of the final animation frames.

Review of Processing in ImPPG
My protocol is now to use ImPPG rather than Registax 3 for sharpening. First, since transparency was changing like crazy during the imaging, ImPPG can rebalance the WP and BP to match image brightness--no need to do it manually in Photoshop. What I thought was amazing about ImPPG is that I could do the surface grayscale inversion, bring out the prominences with curves. and, at the same time, optimize the Lucy-Richardson Deconvolution (sigma=2.3,500 iterations), as well as the unsharp mask (sigma=8, 1.56,). Interesting is that both optimal settings were similar for both days. This time the noise was less prevalent, so no need to reduce the unsharp mask in the fainter areas.

As I mentioned previously, I love that I can see immediately what the final image was going to look like and thus quickly optimize it. And it is very fast, even with full surface imagined at 16 bit and 1.5X drizzle, adjustments over the whole image were nearly instantaneous. All the settings can be saved and then a batch processing does all the images.The color and gif animation were done in Photoshop to complete the animation. 

My Layman’s guide to the “Top 10 things to see in Solar Ha.”
This guide continues to be very popular, so for those that missed my previous posts, I’m including again my list of the Top 10 things to see in Solar Ha. Our Sun in Ha has so many interesting features that it challenging to understand exactly what one is seeing.  I compiled this summary of as a viewing aid for myself, hopefully you may find it useful too.

In white light we only see the Sun’s 6000 Kelvin photosphere “landscape”, consisting of:
•    Darker, cooler sunspots
•    Granulation, consisting of hotter and brighter rising; and cooler and darker sinking convention cells, like boiling porridge.
•    Faculae, bright hot patches of concentrated magnetic flux.

It is the chromosphere that shows up In Ha, as we block out the Photosphere’s overwhelming white light. The chromosphere is a much hotter, 2000 km thick layer, lying above the Photosphere. With temperatures rising to 17000 K, the chromosphere efficiently excites hydrogen to produce Ha emission. 

The chromosphere shows a very different “landscape” than the Photosphere:
•    Spicules, tiny bright spikes, form a 3,000-10,000 km layer of bright fuzz on the Sun’s limb, and darker spikes on the solar disk. They are dark on the disk as they are cooler than the chromosphere below them. Few last more than 15 min, but the Sun has 100s of thousands of them at any one time.
•    Fibrils are tiny low contrast darker filament-like structures. 
•    Dark Mottles, comprised of fibrils and spicules, blanket the entire disk. 
•    Field Transition Arches are groups of longer fibrils that join areas of opposite magnetic polarity.
•    Prominences loop out from the limb: these are glowing, but cooler, hydrogen gas lifted from the Sun by magnetic fields. Prominences rise 100s of thousands of km above the hotter chromosphere.
•    Filaments are the darker clouds that seem to float on the solar disk. Filaments are prominences, appearing darker because they are cooler and higher, extending above the hotter chromosphere below them.
•    Plage (French for beach) are irregular, bright patches on the solar disk, found around active regions. They mark nearly vertical emerging or reconnecting magnetic fields and can last several days.
•    Ellerman bombs (named for the astronomer who studied them) are tiny, brighter spots that fluctuate in brightness, associated with large plage.
•    Flares show a brightening within a sunspot group, often with a “comb-like” flow.  They last from a few minutes to hours and change in both intensity and area as you watch.
•    Sunspot umbrae are the dark cores of sunspots, much like what is seen in white light. However, sunspot penumbrae branch out into whirls consisting of fibrils and spicules. 

Bonus, not in the Top 10, because it is difficult to observe:
•    The Chromospheric Network is outlined by filigree, which are very tiny bright spots that are less than 1 arc-second in size, and best observed off-band of Ha.

Note that it is common to invert light and dark on the solar surface, which provides improved contrast for the solar disk, and a better brightness match to the fainter prominences. It also has the advantage that the otherwise dark filaments on the surface (which are prominences) are now bright, matching the bright prominences at the limb.