Staring @ the Sun, 70

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5/11/2014. It's been nine months since my last confession... Trees hide the Sun for more and more of the year and only in the last few days have I found abundant sunshine out by the telescopes. I put the Lunt 60, double stacked, on the G11 mount and admired the view, then found that the Dell Latitude D820 had failed completely when I tried to take some images. Fortunately, it is so far behind the curve that I could buy another off eBay for $75 and swap out the hard drive, hybrid drive, memory, etc. It was good to go within an hour. Today, I mounted the Lunt piggyback on the AT10RC and gave it a try.

For imaging, I missed the image scale of the frankenscope, so I reassembled that and played with it in the afternoon. Seeing was dreadful, but there were many active regions and if I kept after them, sooner or later I figured I'd catch a steady interlude. Around three o'clock, the active region just west of the one I had been watching launched a C3 flare.

It all comes back. I took 1500 frames of each interesting area (AR 2055 and AR 2056, flaring), stacked the best 100 frames from each clip in AVIStack2 (applying a flat made from 50 defocussed frames from a nearby boring area of the Sun), assembled the mosaic in Photoshop, and then applied histogram adjustments and deconvolution to the TIFF output using PixInsight. With marginal focus and horrible seeing, the exact parms of the deconvolution pass mattered even more than usual. But in the end, the results were not bad ("view image" for a somewhat larger rendition):

smoky flare

Best 100 of 1500 frames, 2 clip mosaic
90mm Orion, Lunt60Tha, ASM120MM
AVI captured in 8 bits
5ms with gain as needed, but quite low.

Then the power supply overheated, and I remembered that I still need to work out some ventilation for the power and data distribution box. (That will also be needed in order for the Robofocus controller to experience ambient temperatures so that its temperature compensation code can work for me in the deep sky.)

Before and after this action, I captured a few other get-reacquainted views:

sparks 1

Best 500 of 1500, single clip.
Minor sparking (Ellerman bombs?) in AR 2055
Other techbits the same.


more sparks

Best 100 of 1500, two clips
Fading C3 flare in AR 2056
Other techbits unchanged.

2014/5/12. Another clear (but not so steady) day. More practice, this time a four panel mosaic. Some unpleasant artifacts arise during the decon steps, and I need to figure out how to get the best from the process without so much of the liability.



Best 75 of 500, four clips
AR 2055 and 2056


I don't know why I get good seeing in the mid-afternoon, but it seems pretty common. After flipping over the merdian, I relocated the Gamma control in FireCapture and experimented with it set to "0" rather than the default "50" -- contrast on the screen is much better, which makes focusing surer, if nothing else. I also boosted gain to ~45 in order to keep exposure time near 5 ms to make use of flickers of exceptionally good detail.



5/16/2014. Still working on a reliable workflow. More practice under a busy Sun. Each clip was 500 frames long; I used the best 75 frames from each. The top frame is a 4-frame mosaic; the others are single clips. Gain +45, exp 5ms, gamma = 0.




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Except where noted, solar photos are made with a ZWO Optical ASI120MM camera (ca. June 2013) behind a Lunt Solar Systems 60mm THa with its objective replaced by an Orion 90mm F10 achromat. The telescope uses a B600 blocking filter and is mounted piggyback with an Astro-Tech 10-inch Ritchey-Chretien (carefully capped!) on an Astro-Physics Mach1GTO mount. A Dell Latitude notebook running FireCapture provides camera control and capture services via USB 2.0. Images typically begin as 400 - 1200 frame AVI's captured at about 27 fps. Clips are aligned and stacked using AVIStack 2.0. The resulting files are processed via wavelet functions in Registax and / or the FocusMagic 3.0.2 deconvolution plug-in in Photoshop CS4. Alternatively, PixInsight picks up the processing somewhere in the workflow after AVIStack processing. The imaging train usually includes an Orion "Shorty" 2x barlow screwed into the ASI120MM body. A RoboFocus motor with a timing belt looped around the stock (or, sometimes, a Feathertouch) focus knob enables remote operation.



                   © 2013, David Cortner