H-beta and H-alpha, full-disk SHG at 700mm FL (and a big ejection)

I LOVE finding out about different ways to appreciate the Sun and light in general. Use this forum to post your info or questions about various outside the mainstream ways to appreciate our life giving star!
Post Reply
thesmiths
Almost There...
Almost There...
Posts: 1053
Joined: Mon Jun 04, 2012 8:13 pm
Location: London, England
Has thanked: 42 times
Been thanked: 1485 times

H-beta and H-alpha, full-disk SHG at 700mm FL (and a big ejection)

Post by thesmiths »

I don't recall trying H-beta before as it was somewhat featureless in the images I had seen. But with my new full-disk, high spatial resolution capability (due to the long chrome-on-quartz slits), I am pleasantly surprised by the gentle and subtle features that H-beta can show. Fortuitously, the Sun is covered with complex and detailed structures at the moment (June 17). Click on the image for a full-size view (there are lots of small details).

H-beta (left) and H-alpha (right). SHG at 700mm FL, 106mm aperture, 9 micron x 12 mm slit, ZWO 183MM camera, 2400 l/mm grating, 100mm f4 optics.
H-beta (left) and H-alpha (right). SHG at 700mm FL, 106mm aperture, 9 micron x 12 mm slit, ZWO 183MM camera, 2400 l/mm grating, 100mm f4 optics.
143249_131735_clahe_small.jpg (486.93 KiB) Viewed 563 times

I find the side-by-side comparison quite fascinating -- because of which features they have in common and also how many structures do not appear at all in H-beta.

I tried to keep the setup parameters as similar as possible; the file numbers are British Summer Time timestamps (the H-beta was actually done first). The shutter speed for H-beta was 0.5ms, the gain was 7% and the fps was 247; for H-alpha, it was 1.0ms, 23% and 224 fps (there is much more light at H-beta). The scan speeds were 12x SR and 10x SR.

I noticed there was the lift-off of a big structure caught on the images taken in H-alpha between 13:13:21 UTC and 13:14:49 UTC. I took a break to do some processing of the data already taken and when I returned to imaging at 13:32:39 UTC, I could no longer see the lifted-off structure. Below is an image of the structure (in the bottom right corner):

H-alpha SHG image showing lifted-off structure (13:13:58 UTC).
H-alpha SHG image showing lifted-off structure (13:13:58 UTC).
141409_clahe.jpg (131.52 KiB) Viewed 563 times


thesmiths
Almost There...
Almost There...
Posts: 1053
Joined: Mon Jun 04, 2012 8:13 pm
Location: London, England
Has thanked: 42 times
Been thanked: 1485 times

H-beta and H-alpha, full-disk SHG at 700mm FL (and a big ejection)

Post by thesmiths »

Some more experimental background: the unfiltered solar radiation on the chrome-on-quartz slit does not seems to have have affected the slit after quite a few hours of exposure. I do try to put on the telescope lens cap when I am not imaging (that is probably good advice for all solar equipment). Even the cyanoacrylate glue I used to attach the quartz chip to the copper disk does not show any signs of degradation (however, I do plan on using a different glue next time -- Torr Seal epoxy, which has much better thermal characteristics).

The heat-sunk copper disk makes the M42 extension tubes very slightly warm; but nowhere near as warm as I notice the ZWO 183MM camera gets! The camera claimed it was at 50 degrees C.

I decided to do a little cleaning of both the chrome and the quartz surfaces with some lens tissue and a camera blower. I noticed that the exposed blue chrome oxide seemed to scratch slightly but I don't think that affected the chrome underneath. Nevertheless, it's probably better to be very gentle cleaning the chrome side. I did notice that after cleaning, there was even less "transversallium" than before. Below is a "raw" image (from Valerie's v3.3.0 software) of the H-alpha image shown above:

"Raw" H-alpha SHG image -- reconstruction but no additional processing.
"Raw" H-alpha SHG image -- reconstruction but no additional processing.
143249_raw.jpg (108.64 KiB) Viewed 553 times

This image has only had reconstruction done, with no line removal, geometric correction, contrast enhancement or sharpening. The raw data looks very clean, which I think is an indication of the quality of the slit. Note that a 90 degree rotation and an image flip is required to get to the "correct" orientation. The scan direction is from left to right (scanning was done in DEC). There is also only a small geometric correction required since there is an instrument tilt of less than 1 degree and the scaling factor is close to 1 (well-matched FPS with scan speed).


User avatar
p_zetner
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 1644
Joined: Sun Mar 18, 2012 4:59 pm
Location: Winnipeg, Manitoba, Canada
Has thanked: 166 times
Been thanked: 719 times

Re: H-beta and H-alpha, full-disk SHG at 700mm FL (and a big ejection)

Post by p_zetner »

Your raw data is remarkably clean!
There is always a characteristic “spiky” appearance to features I capture in my spectroheliograms.
I assume this is due to seeing variations over the course of my (slow) scan. What surprises me is that these spiky variations don’t seem to appear in your raw (fast) scans. I would expect that they occur on fractional second time scales and should affect even fast scans.


User avatar
Carbon60
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 14171
Joined: Wed Mar 07, 2012 12:33 pm
Location: Lancashire, UK
Has thanked: 8352 times
Been thanked: 8103 times

Re: H-beta and H-alpha, full-disk SHG at 700mm FL (and a big ejection)

Post by Carbon60 »

Amazing SHG images. Superb. Interesting comparison too.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
thesmiths
Almost There...
Almost There...
Posts: 1053
Joined: Mon Jun 04, 2012 8:13 pm
Location: London, England
Has thanked: 42 times
Been thanked: 1485 times

Re: H-beta and H-alpha, full-disk SHG at 700mm FL (and a big ejection)

Post by thesmiths »

p_zetner wrote: Sat Jun 18, 2022 2:01 am There is always a characteristic “spiky” appearance to features I capture in my spectroheliograms.
I assume this is due to seeing variations over the course of my (slow) scan. What surprises me is that these spiky variations don’t seem to appear in your raw (fast) scans. I would expect that they occur on fractional second time scales and should affect even fast scans.
There is sometimes jaggedness on the edges (like a random sawtooth), which I think comes from atmospheric fluctuations. This is visible in the closeup of the ejection -- that image did not have the highest quality data, compared to the full disk image. But also when you boost the brightness to emphasise the prominences, the edge defects also become more apparent.

By the way, Christian Buil also attributes jaggedness to mount drive issues (he says he sees asymmetry in the scans sometimes). He recommends not having the mount perfectly balanced -- i.e., the mount should always be pushing or pulling slightly against gravity as it scans.

Assuming most natural disturbances have some sort of 1/f distribution (see for example https://www.researchgate.net/publicatio ... nd_climate, the higher you can push the data up in frequency, the better off you will be.


highfnum
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2023
Joined: Sat Nov 24, 2012 2:33 pm
Has thanked: 57 times
Been thanked: 1173 times

Re: H-beta and H-alpha, full-disk SHG at 700mm FL (and a big ejection)

Post by highfnum »

always like the reversal from Halpha bright area to Hbeta dark

never got a good explanation on why that happens

must be something with higher energy levels in h-beta


User avatar
Montana
Librarian
Librarian
Posts: 34526
Joined: Mon Oct 17, 2011 5:25 pm
Location: Cheshire, UK
Has thanked: 17521 times
Been thanked: 8763 times

Re: H-beta and H-alpha, full-disk SHG at 700mm FL (and a big ejection)

Post by Montana »

All I can say is WOW!!!! :bow :bow :bow

Alexandra


Post Reply