H-beta, H-alpha, CaH high-resolution SHG images, June 22

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H-beta, H-alpha, CaH high-resolution SHG images, June 22

Post by thesmiths »

Another good day of weather in London and the SHG was set up for Hydrogen imaging. Rather than try stacking again, which is hard work, I took a huge number of gigabytes of scans and found a few with excellent individual quality. These were full disk images which were cropped to better preserve the resolution and focus on the interesting areas. Clicking on the images will give a better view.

H-beta SHG image, taken at 700mm FL, 106mm aperture, 2400 l/mm grating, 9 micron wide slit, 183MM camera.
H-beta SHG image, taken at 700mm FL, 106mm aperture, 2400 l/mm grating, 9 micron wide slit, 183MM camera.
091030_clahe_crop.jpg (451.1 KiB) Viewed 172 times
H-alpha SHG image
H-alpha SHG image
101001_clahe_crop.jpg (422.06 KiB) Viewed 172 times
H-alpha SHG image
H-alpha SHG image
101001_clahe_small_crop.jpg (150.35 KiB) Viewed 172 times

The exposure for H-alpha was 0.8ms, gain 11%, fps 290, scan time 13s. For H-beta, 0.4ms, gain 8%, fps 289, scan time 13s.

The spectral resolution is approximately 0.16 angstrom of H-alpha and 0.25 angstrom for H-beta. The approximate instrument spatial resolution is 3 arcsec.
Last edited by thesmiths on Fri Jun 24, 2022 12:04 am, edited 2 times in total.


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Re: H-beta and H-alpha SHG high resolution images, June 22

Post by mashby »

I am looking at that with my humble setup. A PST with a Meade electronic EP connected to my TV. What a sight ! It's not anything like that resolution but I see the main things just fine. In fact I set up my camera to make a time lapse vid over hours.


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Re: H-beta and H-alpha SHG high resolution images, June 22

Post by p_zetner »

These are excellent!
I’m a little surprised that you claim a spectral resolution of 0.16 angstroms. How did you measure this?


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Re: H-beta and H-alpha SHG high resolution images, June 22

Post by thesmiths »

I also include a CaH image taken shortly after the H-beta and H-alpha images. For this, I again used my 600mm all-camera lens SGH. This one does not yet have as good resolution as my main one based on a 700mm APO triplet telescope. I again attempted stacking to improve noise, this time with 35 individual CaH scans. Some filaments and prominences are visible. But given that the Hydrogen images turned out so well, the lack of sharpness is likely due to optics issues.

CaH, 600mm, 1200 l/mm grating, 9 micron slit. 35 scans stacked.
CaH, 600mm, 1200 l/mm grating, 9 micron slit. 35 scans stacked.
220622_AS_imppg_small.jpg (110.63 KiB) Viewed 150 times


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Re: H-beta and H-alpha SHG high resolution images, June 22

Post by thesmiths »

p_zetner wrote: Thu Jun 23, 2022 2:14 am I’m a little surprised that you claim a spectral resolution of 0.16 angstroms. How did you measure this?
I only used Ken's SimSpec SHG v1_3b spreadsheet to calculate the spectral resolution, rather than measuring it.


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Re: H-beta and H-alpha SHG high resolution images, June 22

Post by marktownley »

These are very impressive!


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Re: H-beta and H-alpha SHG high resolution images, June 22

Post by thesmiths »

I tried a new approach to the stacking process for the CaH image. I used the best 75% of 35 SHG images (which were already hand selected to some degree) in AutoStakkert. I then used Registax 6 wavelets , followed by a little Photoshop. The result was quite good. It's definitely sharper than the first attempt.

CaH, AutoStakkert best 75% of 35 SHG scans, Registax 6 wavelets.
CaH, AutoStakkert best 75% of 35 SHG scans, Registax 6 wavelets.
220622_AS75_regi6_b.jpg (162.63 KiB) Viewed 114 times

The time consuming part is resizing all the individual SHG images to be the same width since AutoStakkert requires the images to all have the same size. The heights of the scans are all the same but the width depends on how many frames are taken. Also, half the images need to be flipped left-to-right since scans are done in both directions. It's probably possible to automate these steps.


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