H-alpha SHG images from early morning Aug 11

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thesmiths
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H-alpha SHG images from early morning Aug 11

Post by thesmiths »

I woke up early on Thursday morning and took some H-alpha scans before catching a 2pm flight from Heathrow. I processed some of reconstructions on the plane and then managed to find time to do some stacking and Photoshop while on holiday. Doing processing on a laptop is harder than on the big screen of my desktop so the quality might be a little lower than recent results. But the seeing conditions were quite favourable and I was able to achieve good focus across almost the full disk. For a comparison to a full disk etalon image taken later that same day, see viewtopic.php?t=37523.

H-alpha SHG, 720mm focal length, 106mm aperture. 2400 l/mm grating, 9 micron wide lithographic slit (chrome on fused quartz). Stack of 11 (out of 20 frames). AS3!, imppg, Photoshop Elements. ASI 183MM camera. 2ms exposure, gain of 20 (4%). Average fps 289. Scan rate 13x sidereal rate. Scans taken from 7:13 to 7:20 UTC.
H-alpha SHG, 720mm focal length, 106mm aperture. 2400 l/mm grating, 9 micron wide lithographic slit (chrome on fused quartz). Stack of 11 (out of 20 frames). AS3!, imppg, Photoshop Elements. ASI 183MM camera. 2ms exposure, gain of 20 (4%). Average fps 289. Scan rate 13x sidereal rate. Scans taken from 7:13 to 7:20 UTC.
110822-Ha-3-720mm-2400g-stack-11.jpg (1.18 MiB) Viewed 1169 times

The image above is best seen by opening the image in a new tab. I also made some closeups with inverted grayscale (these are crops from the full disk image above). The ones below are best viewed by clicking on the images.

H-alpha SHG, inverted. Crop of the full disk scan.
H-alpha SHG, inverted. Crop of the full disk scan.
110822-Ha-3-720mm-2400g-stack-11_crop1.jpg (559.07 KiB) Viewed 1169 times
H-alpha SHG, inverted. Crop of the full disk scan.
H-alpha SHG, inverted. Crop of the full disk scan.
110822-Ha-3-720mm-2400g-stack-11_crop2.jpg (905.26 KiB) Viewed 1169 times

People are always curious about the setup used to acquire the data. It's actually nothing too fancy, but it was quite a bit of trial and error to get working well. Apart from the lithographic slits that I had specially made, there is nothing that isn't commonly available.

SHG setup. APO triplet refractor, HEQ5 Pro mount. Note the telescope is pointed at the eastern horizon to get the early morning light. This photo was taken just before the Sun rose over the trees.
SHG setup. APO triplet refractor, HEQ5 Pro mount. Note the telescope is pointed at the eastern horizon to get the early morning light. This photo was taken just before the Sun rose over the trees.
1456.jpg (432.2 KiB) Viewed 1169 times

The funny white cover on the end is to block out ambient light. The counterweight on the upper dovetail is a convenient way to keep the apparatus balanced in DEC, which is the scanning direction. Because of the odd (non-symmetrical) shape, the centre of gravity is above the DEC axis; therefore, the balance shifts as the RA advances, so I move the counterweight gradually forward with time. If the DEC is not well balanced, there can be scanning errors (typically in one direction).
Last edited by thesmiths on Sun Aug 14, 2022 5:04 pm, edited 3 times in total.


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Re: H-alpha SHG images from early morning Aug 11

Post by marktownley »

Lovely images Douglas, I hope you had a great holiday.


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Re: H-alpha SHG images from early morning Aug 11

Post by Carbon60 »

Absolutely superb SHG images, Douglas. Really very nicely done.

Stu.


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Re: H-alpha SHG images from early morning Aug 11

Post by Montana »

Wow!! your images are absolutely superb :bow :bow :bow I love seeing what you get :)
Have a great holiday!

Alexandra


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Re: H-alpha SHG images from early morning Aug 11

Post by thesmiths »

Normally, the spectroheliograph is best for surface structure (filaments in particular), but prominences are also observable. I processed this crop to bring out the prominences in one particular region. I don't think the very narrow bandwidth of the SHG gives any advantages for prominence imaging so I normally don't make the effort to do special processing to bring them out in isolation to surface features, which are generally more impressive in SHG images.

H-alpha SHG, prominences
H-alpha SHG, prominences
110822-Ha-3-720mm-2400g-stack-11_prom.jpg (311.26 KiB) Viewed 1119 times

Note that all the images here were from the same imppg output file (22.3 MB in size, 3408 pixels high) and then treated in different ways in Photoshop Elements. The 20 SER files that went into creating the reconstructed PNG images (used for generating the AS3! stacked image) were 77.2 GB in size.


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