Staring at the Sun, 5

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6/22/2010. No photos worth showing off today. But here are a few lessons that need to get posted when there is next any news worth sharing:

  1. The 10.5mm TeleVue Plossl in a 1.25-inch eyepiece projection adapter comes to focus nicely and provides a usefully large image scale. So, though less so, does just adding the barlow lens to the end of the adapter and using it as an extension tube. High cloudiness made real tests of both configurations useless, but these two passed plausibility checks very nicely. I bumped the camera to ISO800 and used anything from 1/10 to 1/2 second.
  2. On a 95oF day, hazy Sun or no, the Pyramid power supply will overheat, turning off the telescope electronics and scaring the bejezuss out of anyone with a vested interest in the gear. (6/23: Keeping the power supply in the shade of a lawn chair allowed it to work all day on a sunny 98oF day.)
  3. I ordered an observing hood from Sierbert Optics, black inside, white out, made for both night and H-a viewing. (Two days later, Henry Seibert sent me an invoice for my Paypal transaction; two words for Henry: "Shopping cart.") It will beat wadding a black garbage bag around my head to focus the camera or peer into the eyepiece.
  4. On the 20th, I missed a helluva big prominence
  5. On the 21st, I didn't miss much of anything.



Same scale as previous images, cropped. 1/8 second, ISO 400.
LS60THa, double-stack. Canon 50D.


6/23/2010. As feared, the 90mm Losmandy mounting rings are too small for the solar 'scope's tube. They're also too small for the ST80 guide scope. But they're just right for that brass tube I've been slowly outfitting to rebuild a 3-inch Unitron. They attach via 10-24 machine screws to a mounting plate to be provided by the user. So now I know how I will attach the rebuilt Unitron to its mount (I finally have some ideas about how to repair the polar axle that snapped in shipping a Unitron equatorial home from New Mexico Skies ten years ago).

In other solar news: under today's much clearer skies, I confirmed that the 10.5mm TeleVue Plossl gives a nice view of the Sun (I begin to wonder if there is any eyepiece that doesn't). It's a good middle ground between the small but immaculate image in the 20mm Plossl and the detailed but dim image in the 7mm Nagler. Under clearer skies, the 10.5 provided a lovely scale and excellent detail when focusing the 50D with Liveview. Even so, I've yet to get even one decent image from that configuration. The exposure needs to be about 1/4 second at ISO400 (1/20 at 2000 works better for detail, but noise is lethal). The results are terribly fuzzy no matter what I've tried. This image scale may simply be asking too much of the 50mm aperture. I would be more certain of that except that I've seen exquisite images online from the 50mm front filter. It seems that a webcam or a monochrome video camera may be required for close and detailed views; there is still some hope that a better, more refined technique will do.

When using the stock Crayford focuser for critical focusing of a heavy and somewhat cumbersome image train, you must carefuly adjust both the lock screw and the tensioning screw. Today I added a couple of moderately stretched rubber bands to take on some of the weight of the Canon and eyepiece projection adapter. The elastic bands allowed both the coarse and fine focus knobs to lift the load vertically (the Sun was nearly overhead).


6/24/2010. I tried several versions of webcam capture software this morning (Iris, Debut, WxAstro Capture, and 2 versions of K3CCD). I was looking for a combination that would allow my Philips Vesta Pro to capture AVI's that will work gracefully with Registax (either v2 or v5.1). "Gracefully" means without my having to hunt and load a specific codex. In the end, I got the most satisfaction out of the freeware version of K3CCD Tools and I remain undecided between the simpler, early (2003) Registax or the more complex and capable current edition (v5.1). What I have not got yet is a decent image of disk detail.

Just as I got a kit together to try for that, heat shut down the power supply again (I forgot to shade it while concentrating instead on shading me and the computer screen). S'OK: I captured several 10 second drifts of the Sun across the chip and had great fun watching Registax lock onto a prominence and align and stack the moving image. Thus, 100 frames at 10 frames per second, 1/50 second each, aligned and stacked:


webcam prominence


That doesn't seem like an improvement over what I can get with the DSLR. I could see projected disk detail on the computer screen, and single frame snapshots confirm that the webcam can capture it. Carefully adjusted clips (45MB each!) show some disk features, but none of the video clips reveal as much detail as I could easily see, still less do they capture the wealth of hidden detail I hope to get from stacked frames.

About 4:30, I found surprisingly steady air, so I tried a few frames with the 50D and extended barlow (that is, the barlow but no eyepiece in the eyepiece projection extension). I was actually trying for disk detail with the stacked filters, but the best of the bunch was this longer exposure of limb detail:


single stack

Canon 50D, 1/4 second, ISO 400, single etalon.
Click the image for a 1280 pixel version


I extracted the red Bayer plane using Maxim DL5 from two consecutive 1/4 second exposures. A surprising amount of disk detail showed up. I saved them as 16-bit TIF files, overlayed them in Photoshop to reduce grain, and then went to work to extract good tones and detail from the disk. Finally, I laid the finished disk image back on the prominence image above. So here is a composite from two 1/4 second frames, merely treated differently to get edge and disk detail:



Click the image for wallpaper.


Focusing may not be everything, but it's a lot.



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                   © 2010, David Cortner