H-alpha and Ca-H full disk images from 6 Aug -- very good resolution

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thesmiths
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H-alpha and Ca-H full disk images from 6 Aug -- very good resolution

Post by thesmiths »

London has had a streak of nice days of weather so I've taken the opportunity to keep practicing with our updated SHG. Today's seeing was better than yesterday and the SHG images were noticeably sharper. For the Calcium imaging, I chose the Ca-H line (it is a little narrower than Ca-K, which makes it easier to acquire data) and I used a 72mm aperture mask, bringing the focal ratio down to f10. The results are probably our best so far -- focus is now very good across almost the full disk at 720mm focal length. The quality now depends mainly on the atmospheric conditions.

Comparing to images on the same day from Rainer, the quality of full-disk SHG images in H-alpha are now similar to good etalon images https://rainerehlert.com/00_SCHForum/20 ... _9Q_RE.jpg (I'm not sure if Rainer's images are single or double stacked and what aperture he used -- maybe someone can let me know). Full-disk Calcium SHG images are now likely better, or at least more revealing, than Calcium filter images.

H-alpha SHG, 106mm aperture, 720mm focal length (triplet APO). 2400 l/mm grating, 9 micron wide lithographic slit. 14x sidereal scan rate. Stack of 11 frames (out of 20). AS3!, imppg, Photoshop Elements.
H-alpha SHG, 106mm aperture, 720mm focal length (triplet APO). 2400 l/mm grating, 9 micron wide lithographic slit. 14x sidereal scan rate. Stack of 11 frames (out of 20). AS3!, imppg, Photoshop Elements.
060822-Ha-4-7200mm-stack-11.jpg (2.23 MiB) Viewed 1123 times

All images look best when opened in a new tab.

H-alpha SHG, inverted.
H-alpha SHG, inverted.
060822-Ha-4-7200mm-stack-11_invert.jpg (2.23 MiB) Viewed 1123 times

I think the inverted H-alpha image above looks interesting next to the Ca-H image below:

Ca-H SHG image. 720mm focal length, 72mm aperture. 2400 l/mm grating. 13x sidereal scan rate. Stack of 9 frames (out of 24).
Ca-H SHG image. 720mm focal length, 72mm aperture. 2400 l/mm grating. 13x sidereal scan rate. Stack of 9 frames (out of 24).
060822-CaH-720mm-72mm-2400g-stack-9.jpg (2.15 MiB) Viewed 1123 times

Here is a closeup of one of the fairly active regions in H-alpha, taken from a different set of scans than the full disk image above. It looked quite nice inverted.

H-alpha SHG, inverted. Stack of 7 (out of 18).
H-alpha SHG, inverted. Stack of 7 (out of 18).
060822-Ha-2-720mm-stack-7_crop_invert.jpg (710.56 KiB) Viewed 1123 times

And, finally, here is the same region in Ca-H, taken from the full disk image above.

Ca-H SHG.
Ca-H SHG.
060822-CaH-720mm-72mm-2400g-stack-9_crop.jpg (734.28 KiB) Viewed 1121 times
Last edited by thesmiths on Tue Aug 09, 2022 8:56 pm, edited 1 time in total.


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Re: H-alpha and Ca-H full disk images from 6 Aug -- very good resolution

Post by marktownley »

Stunning results Douglas!


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Re: H-alpha and Ca-H full disk images from 6 Aug -- very good resolution

Post by Montana »

Your discs are absolutely breath taking, your CaH makes my heart sing :bow :bow :bow

I think Rainer uses a DS Coronado 60mm

Alexandra


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