H-beta and Ca-H SHG at 480mm focal length, July 23

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thesmiths
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H-beta and Ca-H SHG at 480mm focal length, July 23

Post by thesmiths »

It seems the big heatwave in London has left behind not the best seeing conditions. Working with the large 106mm aperture telescope didn't give such good results and in general the fine details in H-alpha could not be resolved well. We therefore went with our 80mm aperture, 480mm focal length setup and concentrated on Ca-H and H-beta.

We again decided to observe Ca-H with a somewhat lower spectral resolution (using a 1800 l/mm grating). The resolution with this setup is theoretically about 0.3 angstroms (vs around 0.2 angstroms with a 2400 l/mm grating). This reduces the contrast somewhat, which eliminates the most of the saturated levels (although perhaps reduces the visibility of filaments and prominences somewhat).

We also did a quick experiment with H-beta. Using the same 1800 l/mm grating, we used this in second order, giving a very high spectral resolution equivalent to using a 3600 l/mm grating. This gave an extremely narrow theoretical spectral resolution of around 0.1 angstrom (a 2400 l/mm grating would have given around 0.2 angstrom). H-beta images are generally not as high contrast as H-alpha so the narrower bandwidth might enhance surface details somewhat.

H-beta and Ca-H SHG images. 80mm aperture, 480mm focal length. 1800 l/mm grating (in 1st order for Ca-H and 2nd order for H-beta). H-beta stack of 8, Ca-H stack of 15. July 23.
H-beta and Ca-H SHG images. 80mm aperture, 480mm focal length. 1800 l/mm grating (in 1st order for Ca-H and 2nd order for H-beta). H-beta stack of 8, Ca-H stack of 15. July 23.
230722-Hb-480mm-3600g-CaH-1800g.jpg (969.63 KiB) Viewed 981 times

Although conditions were not optimal to resolve fine spatial details, I think qualitatively this H-beta image does show more surface contrast than our previous efforts (see viewtopic.php?t=36970). I think it might be worthwhile to give the high spectral resolution treatment to H-beta another time when conditions are more favourable. By the way, it was necessary to keep a H-beta filter in front of the camera to do "order sorting" (filter out long-wavelength 1st order components), otherwise the spectrum was very washed out.


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Re: H-beta and Ca-H SHG at 480mm focal length, July 23

Post by Montana »

You are managing to get some awesome images, I could sit for ages looking at the similarities and differences between these two
:bow :hamster:

Alexandra


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Re: H-beta and Ca-H SHG at 480mm focal length, July 23

Post by hopskipson »

Hi Douglas,
I’m just trying to digest as much information on sgh while I’m on vacation away from my solar set up. How did you perform this experiment?

“We also did a quick experiment with H-beta. Using the same 1800 l/mm grating, we used this in second order, giving a very high spectral resolution equivalent to using a 3600 l/mm grating.”

Nice images by the way!


James
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