Spectroheliograms recorded last summer.

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p_zetner
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Spectroheliograms recorded last summer.

Post by p_zetner »

Hello Everyone.

This is a follow up post to the thread "A New Spectroheliograph" viewtopic.php?f=8&t=30793.
I made a few tests of the device this past summer to understand its quirks and foibles. Here are spectroheliograms taken at H-alpha and Ca-K wavelengths on 15 June 2021. There is a nice arch prominence visible.
Series_med_montage_092458_104109_v2_siz.png
Series_med_montage_092458_104109_v2_siz.png (1.22 MiB) Viewed 1196 times
The spectrometer is a modified Bausch & Lomb monochromator and its peculiar design causes the spectrum image to be skewed as shown in the figure below.
092458_single vid frame proc comparison_siz.png
092458_single vid frame proc comparison_siz.png (151.38 KiB) Viewed 1229 times
The upper spectrum is a frame from the video that was captured. It shows the skew as well as the usual problems of rotation, "smile" and transversalium that need to be corrected. I use VirtualDub for my spectrum video processing and, fortunately, there are video filters ("General Quadrilateral Transform", "Rotate2" and "Barrel Distortion") which can correct the geometric problems of skew, rotation and smile. The lower frame in the above image shows the result of applying these filters as well as the effect of a flat-frame process to correct image intensity uniformity (vignetting) and reduce the visibility of the transversalium. By the way, the prominent vertical bar in the lower frame (tilted, near-vertical bar in the upper frame) is due to the presence of a sunspot (near NW limb). It’s not transversalium.

The results with this device are reasonable (with some room for improvement). The minimal extra work in correcting the skewed spectrum is offset by the handy counter attached to the grating drive of the monochromator which allows extremely easy wavelength setting in the field. My original intent was to use it for the UV portion of the spectrum but my current plan is to make it my "workhorse" for coverage of the entire visible and near-uv spectrum. My original SHG has now been configured for use in the uv by installing a 3600 lines/mm grating to achieve high spectral resolution.

Hopefully, some day soon the snow will melt, the skies will be clear and I can resume some SHG imaging.

Cheers.
Peter
Last edited by p_zetner on Sat Mar 19, 2022 4:00 am, edited 3 times in total.


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Re: Spectroheliograms recorded last summer.

Post by rsfoto »

Hi Peter,

Very interesting


regards Rainer

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Re: Spectroheliograms recorded last summer.

Post by Montana »

Nice work Peter, that prominence falls straight into the March imaging challenge :hamster: very interesting indeed :bow

Alexandra


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Re: Spectroheliograms recorded last summer.

Post by p_zetner »

Thanks Rainer and Alexandra.
It seems I did nail the March challenge.....almost a year ago!
Cheers.
Peter


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Re: Spectroheliograms recorded last summer.

Post by christian viladrich »

Very interesting Peter.
Thanks for sharing.


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Re: Spectroheliograms recorded last summer.

Post by marktownley »

Looks good!


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Re: Spectroheliograms recorded last summer.

Post by p_zetner »

Here are a couple more spectroheliograms from the 15Jun2021 session.
They show the solar disk at the CN molecular bandhead (3883 A) and the H beta line (4861 A).
I present them as montages with the Ca K and H alpha images for comparison.

The CN disk is largely photospheric with faculae occupying the same locations as plage in the Ca K image, plage being more diffuse. The CN disk is closely comparable to a wideband Ca image, largely representing the near uv continuum. The H beta disk, roughly equivalent to a detuned H alpha image, shows the chromospheric network as Ca K does but in a dark pattern rather than light. Prominences are visible in the chromospheric images, H alpha, Ca K and H beta.

Cheers.
Peter
Series_med_montage_111450_104109_siz.png
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Series_med_montage_092458_102449_siz.png
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Re: Spectroheliograms recorded last summer.

Post by marktownley »

An informative comparison there Peter, thanks for sharing!


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Re: Spectroheliograms recorded last summer.

Post by highfnum »

cak proms
real clear


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Re: Spectroheliograms recorded last summer.

Post by p_zetner »

Thanks Mark and John.

Here is the last of the batch: the helium D3 chromospheric line.

Cheers.
Peter
EQW_CI_Montage_proc2_frame_siz.png
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Re: Spectroheliograms recorded last summer.

Post by marktownley »

Nice addition Peter!


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