14May2019 Spectroheliograms: H alpha

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14May2019 Spectroheliograms: H alpha

Post by p_zetner » Thu Sep 12, 2019 9:31 pm

Hi Everyone.

I've posted a teaser collage of the Sun in four wavelengths in the main forum.
viewtopic.php?f=4&t=26584&p=239629#p239629

I thought I would add some more images here and start with H alpha.

The first three images are, in order, full disk H alpha spectroheliograms taken at line centre, line centre plus 0.74 Angstroms and a Dopplergram (+/- 34 km/s ).
Ha_dsk_EQW_Montage_AVG_proc01_shrp.png
Ha_dsk_EQW_Montage_AVG_proc01_shrp.png (3.18 MiB) Viewed 2406 times
Ha_dsk_EQW1_Montage_AVG_proc01_shrp.png
Ha_dsk_EQW1_Montage_AVG_proc01_shrp.png (3.58 MiB) Viewed 2406 times
Ha_dsk_DOP_Montage_AVG_proc_H_proc01_shrp.png
Ha_dsk_DOP_Montage_AVG_proc_H_proc01_shrp.png (3.63 MiB) Viewed 2406 times
For this imaging session, I wanted to try to increase the image scale and zoom in on the solar surface a little so I attached a Celestron 3x barlow to the Celestron NexStar 4 telescope which comprises the front end of the spectroheliograph. I didn't have a lot of optimism for this arrangement because I thought that seeing effects would be terribly bad at this expanded image scale. To my pleasant surprise, the results aren't too bad! Only a portion of the surface is imaged as a strip produced by the Sun drifting across the FOV. Here are the results, once again presented in the order line centre, line centre plus 0.74 Angstroms and a Dopplergram (+/- 34 km/s ).

Open these in a separate window for full size.
Ha_AR_EQW0plus080CI_proc_H-09ctrst_proc00_shrp.png
Ha_AR_EQW0plus080CI_proc_H-09ctrst_proc00_shrp.png (3.96 MiB) Viewed 2406 times
Ha_AR_EQW1plus080CI_proc_HV-06ctrst_proc01_shrp.png
Ha_AR_EQW1plus080CI_proc_HV-06ctrst_proc01_shrp.png (5.2 MiB) Viewed 2406 times
Ha_AR_DOP_proc_HV-08ctrst_proc01_alt_shrp.png
Ha_AR_DOP_proc_HV-08ctrst_proc01_alt_shrp.png (4.82 MiB) Viewed 2406 times
Comments and questions welcome.
Regards.
Peter

By the way, here’s the most recent version of the spectroheliograph:
2990D809-3F54-4DE8-B015-91F4D7764C9E.jpeg
2990D809-3F54-4DE8-B015-91F4D7764C9E.jpeg (2.33 MiB) Viewed 2402 times



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Re: 14May2019 Spectroheliograms: H alpha

Post by marktownley » Fri Sep 13, 2019 5:15 am

These are great images Peter! I'm assuming the C4 is not front filtered at all - do you have no thermal issues with it?


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Re: 14May2019 Spectroheliograms: H alpha

Post by p_zetner » Sun Sep 15, 2019 3:22 am

Hi Mark.
So far, I haven’t used any front filtering on the C4 but I’m thinking about it. In the previous incarnation of this SHG, I used a Rubinar 100mm f/10 which had some cemented field correcting lenses at the back end. I used a 100mm x 100mm Schneider IR-UV cut filter to try and reduce the thermal load on those lenses. I plan to add the Schneider filter to the C4 in the present arrangement. The SHG is very prone to seeing and thermal effects so it’s hard to tell if front filtering is necessary or beneficial but it’s probably a good idea to protect the optics.
Cheers.
Peter



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Re: 14May2019 Spectroheliograms: H alpha

Post by Montana » Tue Sep 17, 2019 9:25 am

These are terrific images Peter :bow how did you produce the dopplergram?

Alexandra



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Re: 14May2019 Spectroheliograms: H alpha

Post by p_zetner » Wed Sep 18, 2019 8:42 pm

Hi Alexandra.

Thanks for the kind comment. I've attached a picture which gives a brief idea of how the dopplergram is constructed and what it shows. The explanation is a bit sparse but, hopefully, the idea comes through. Unlike a regular image in which the grayscale variations are due to the brightness variations of solar features, the dopplergram grayscale variations are proportional to line of sight velocities of the features, regardless of their intensities.
Dopplergram.png
Dopplergram.png (229.75 KiB) Viewed 2322 times
The montage below shows the (cropped) dopplergram (+/- 34 km/s) posted above after it has been colourized and superimposed on a spectroheliogram of the continuum at 656 nm and also superimposed on an H alpha spectroheliogram. In the colourized dopplergram, blue shows approaching gas and orange represents receding gas (infalling gas). The continuum spectroheliogram is shown in (a) and the dopplergram is superimposed in (c). The H alpha spectroheliogram is shown in (b) and the superimposed dopplergram is shown in (d). An interesting feature is the bright orange visible at the exterior boundary of the spot penumbra in (c). Quiescence over the penumbra itself and relatively fast flows at the exterior boundary seem to be the norm. (Leighton, Robert B., Noyes, Robert W. and Simon, George W. (1962) “Velocity Fields in the Solar Atmosphere, I. Preliminary Report” Ap.J., v135, p47. http://adsabs.harvard.edu/abs/1962ApJ...135..474L)
DOP_continuum-plus-Halpha_composite_montage_crop_lbsl.png
DOP_continuum-plus-Halpha_composite_montage_crop_lbsl.png (12.25 MiB) Viewed 2322 times
All the best.
Peter



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Re: 14May2019 Spectroheliograms: H alpha

Post by bart1805 » Wed Sep 18, 2019 8:58 pm

Wow! And I thought that my image train was long....
Thanks for the explanation and images. Be gentle to your heart, take care!



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Re: 14May2019 Spectroheliograms: H alpha

Post by p_zetner » Thu Sep 19, 2019 12:09 am

Thanks for your comment and kind wishes, Bart!

The optics train is long but pretty sturdy. One thing about this type of spectroheliograph is that, generally, it doesn’t need to track. It remains stationary as the Sun “sweeps past”. I think, because of that, there’s more tolerance of flexure and other mechanical issues. The SHG stays well aligned, though, for many observing sessions and that’s with me hauling it out of the basement each time! I’ve actually improved the stability of the mounting somewhat since this photo was taken.

Cheers.
Peter



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Re: 14May2019 Spectroheliograms: H alpha

Post by Carbon60 » Thu Sep 19, 2019 5:44 am

Excellent work, Peter. Is there any specific reason for selecting +/- 34km/s?

Keep well.

Stu.


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Re: 14May2019 Spectroheliograms: H alpha

Post by Montana » Thu Sep 19, 2019 7:12 am

Wow! thanks for the excellent explanation :)

Alexandra



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Re: 14May2019 Spectroheliograms: H alpha

Post by LTHB » Thu Sep 19, 2019 5:59 pm

Hi Peter!

the more of your images I see, the more I feel I should start to build my own SHG! Extremely interesting project, thanks for showing!

Frank



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