The Sun’s Awake!

It’s been a quiet month on the astro front unfortunately; mostly cloudy skies with the odd exception on certain nights. When it was clear though, I would either be battling a full moon or the seeing was truly terrible, causing horrible gradients in my images and huge guiding errors. No good for hours upon hours of integration on a target.

However, last weekend we had some really nice weather during the Sunday afternoon, and so I decided to try out some white-light solar observing again after my half a dozen previous failed attempts. I had noticed online that the sun was becoming increasingly active during the previous week, with a nice group of sunspots traveling across the solar disk. Fortunately, they were in prime position to be captured by the time I was able to set up!

So I set my telescope up on the patio as per usual, however as it was daytime I couldn’t polar align the mount at all. So all I could do is try to minimise any errors that could possibly be introduced into the system, such as perfectly facing the rig north by using a compass and getting the tripod as level as I could by using a circular bubble level. I didn’t think it would slew straight onto the sun, but what’s the harm in doing everything properly?

Full Rig With Built-In White-Light Solar Filter

As expected, it was nowhere near the on the initial slew. However, by using the corkscrew search feature of EQMOD, I was eventually able to see the white edge of the solar disk. From there on I could manually slew the telescope directly over the entire disk, and set the tracking to solar instead of the usual sidereal. A necessary step I later found out!

The FoV of the Sky-Watcher 130PDS in combination with the Canon 600D is perfect for solar and lunar observations, as seen below. And using the EOS Camera Movie Record software for windows enables 5x digital zoom while recording video, so I can capture amazing close up detail using this method, at the cost of resolution of course. Even so, the final result is around the size of a 1080P video and is easily scalable back to full resolution within software.

Sky-Watcher Explorer 130PDS & Canon EOS 600D Field of View

The most difficult part with solar observing is getting the telescope accurately focused. The focus position isn’t quite the same as for when taking deep sky objects. Naturally, the sun is a lot closer to us than a galaxy millions of lightyears away. And because the sun is a sphere with a diameter of just under 1.4 million km across, the focus point will change depending on what part of the sun you are intending to focus on. If it is focused on the defined edge of the sun, to catch prominences for example, any details on the surface may become blurred. Likewise, if you focus on the centre band of the sun where the sunspots usually pass through, the hard edge becomes less defined.

Getting to that point entirely though without an electronic focuser is extremely difficult, as you’re constantly battling the glare of the sun on the scope and camera screen. Furthermore, just being able to see anything of that high detail to accurately judge focus on a 3″ screen, even with 10x digital zoom, is nigh-on impossible! It’s usually a case of take an exposure, and adjust accordingly, but you can be there for many minutes, while all the time clouds are rushing past the sun! However, eventually I got a position that I was happy with.

Speaking of clouds, it wouldn’t be the British weather without them rearing their ugly head! I had managed to get a series of 510-frame snapshot videos before they came racing across the sun, almost completely blocking it from view for a good 15 minutes. All the time, it was slowly dropping in altitude and I was soon going to lose it behind my neighbours garage!

Snapshot along the viewpoint of the telescope.

Eventually though, they disappeared leaving amazing views of the sunspots, and the atmosphere was surprisingly still for a warm spring afternoon. However, the contrast in the details just weren’t popping out like I had hoped, so I decided to try something unconventional and use my IDAS NBZ dual-band filter to isolate the Hydrogen and Oxygen elements. Surprisingly it worked quite well, and you could instantly see all the currents in the solar surface, as well as the penumbra surrounding the central umbra of each sunspot. I took another series of short 510-frame video clips and chose the best one of the bunch to process.

Firstly I imported the video clip into PIPP (Planetary Imaging PreProcessor) to convert the video clip into a file format that can be processed by AutoStakkert3!. In there, all the individual frames were graded and sorted into an order of good to bad. This process also weeds out all the frames where the atmospheric disturbances were terrible or the mount jolted in the wind, from the perfect frames that were at the moment when the seeing was perfectly stable. From there, the best 5% of those 510 frames were chosen to be stacked together to produce the final image. The final processing was done with Registax 6, where the wavelets were used to really highlight the umbra and penumbra, as well as the surrounding surface detail. All the processing that was done in Photoshop was to add the orange colour back to the white-light image.

Overall, I think I’ve finally cracked the editing stages of converting video frames into a final stacked image!

What do you think? Please let know in the comments!

Best 5% of 510 Frames.

2 Comments Add yours

  1. Ggreybeard says:

    Good results, Adam – and good advice about focusing.

    It’s true that the biggest and brightest object in the sky can be very difficult to locate! Initially I got close by judging the appearance of the shade on the sides of the scope.

    When I bought my Lunt solar scope it came with one of these little gizmos….

    https://luntsolarsystems.com/product/tele-vue-sol-searcher/

    …..and I found it an indispensable tool.

    Like

    1. Thank you!

      And thank you for the advice on the solar searcher, I might have to get one of them in the future. I can see it being VERY useful!

      Liked by 1 person

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