Calcium H images -- with prominences!

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thesmiths
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Calcium H images -- with prominences!

Post by thesmiths »

Versus out last attempt at SHG imaging, we fined tuned the focusing of the optics for the 400nm region and also removed the IR cut filter, which did cut down on the light a bit in that region of the spectrum. The following image shows the solar disk at what we call pixel shift =0, or at the darkest part of the Calcium H line. This gives the most surface contrast. However, we found that the prominences were slightly more defined at pixel shift =2 (which I think is slightly towards the red). So we combined the disk and the prominence outputs from our SHG software from these two slightly different wavelengths to produce the image below. This was taken on Aug 15 so can be compared to the "monster prom" images taken by others in hydrogen alpha. In Calcium, the big proms are not as spectacular but they are impressive nonetheless.

Calcium H disk and prominences
Calcium H disk and prominences
144255_shift=0_2.jpg (114.21 KiB) Viewed 706 times

For completeness, I also included the other hemisphere. Since it did not have particularly strong prominences, this is just the disk alone:

Calcium H disk
Calcium H disk
141908_shift=0.jpg (82.44 KiB) Viewed 704 times

Note that since we scan our SHG in DEC (North and South), the hemispheres are East and West. Our slit is currently not quite big enough to capture the full disk with two scans. Each scan was done at 8x sidereal rate so took about 15 seconds to cover the solar disk. The exposure time was 4.1ms, the FPS was 244 and the gain was 221. The ASI 178MM was used with single binning and the video was captured in 16-bit SER (ROI 2000x200).


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Re: Calcium H images -- with prominences!

Post by DeepSolar64 »

I don't see a lot of Calcium H work here so this was a bit of a surprise. The flexibility of an SHG is awesome!

James


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Re: Calcium H images -- with prominences!

Post by thesmiths »

I had intended to do a comparison of Calcium H and K to see how different the images are. But, as my fellow Canadian, Joni Mitchell wrote, "clouds got in my way".


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Re: Calcium H images -- with prominences!

Post by Montana »

Wow!! these are absolutely superb :bow :bow :bow I really look forward to your work :hamster:

This is probably a daft question as I know absolutely nothing about SHG, but, can you buy a bigger slit to get a full disc?

Alexandra


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Re: Calcium H images -- with prominences!

Post by thesmiths »

Montana wrote: Mon Aug 16, 2021 7:11 am This is probably a daft question as I know absolutely nothing about SHG, but, can you buy a bigger slit to get a full disc?
That is actually an excellent question. I think the length of the slit (and perhaps also the quality) is currently the bottleneck. Ken and I have been pushing the company Thorlabs to produce a 6mm version (their standard is now 3mm). They promise they can come out with the new product by the end of the summer. See the old thread here: viewtopic.php?f=10&t=31177

The French Solex guys use a metal-coated glass slit that is 4.5mm long, so you can just about squeeze in a full disk at 480mm and you can cover 900mm with two scans if you are careful.


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