12 June 2020 Spectroheliograms

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12 June 2020 Spectroheliograms

Post by p_zetner » Sat Jun 27, 2020 3:49 am

Hello Everyone.

Here is a collection of spectroheliograms taken on June 12. There was a bit of a delay in posting because I'm still experimenting with processing techniques. I set the instrument up for full disk views. It had previously been configured for closeups (using a ~3x barlow on the Celestron 4" SCT) and I actually regret having made the change for this session because it would have been more interesting to view the AR and prominence at higher magnification. Chalk it up to rustiness after a long time since last using the SHG. I also replaced the previous 2400/mm grating with a 1800/mm grating. This sacrifices some spectral resolution for better transmission in the UV.

The first montage shows the solar disk imaged in the four Fraunhofer lines: CaII K, H beta, HeD3 and H alpha.
Montage_CaK_Hb_HeD3_Ha_12Jun2020_lbls.png
Montage_CaK_Hb_HeD3_Ha_12Jun2020_lbls.png (587.48 KiB) Viewed 251 times
The second montage shows a series of images in H alpha. The SW limb prominence is evident in the upper frames which are composite images of prominence and disk. A blue wing image shows the expected similarity to H beta shown in the first montage. A dopplergram shows some evidence of complex plasma flow near the AR.
Montage_Ha_disk-proms_blu-wing_doppler_12Jun2020_lbls.png
Montage_Ha_disk-proms_blu-wing_doppler_12Jun2020_lbls.png (588.81 KiB) Viewed 251 times
The third montage shows some images in the UV. These are composite images of prom and disk in the CaII K line. A blue wing CaII K line and an image taken in the CN bandhead (3883 angstroms) show strong similarity. The CN molecular band is interesting because magnetic bright points can be observed there (at high spatial resolution) with greater contrast than in the CH molecular G-band (~ 4300 angstroms). The required spatial resolution would be pretty challenging for a spectroheliograph.
Montage_CaK_proms-disk_blu-wing_CN-band_12Jun2020_lbls.png
Montage_CaK_proms-disk_blu-wing_CN-band_12Jun2020_lbls.png (643.59 KiB) Viewed 251 times
The SW limb prominence exhibited some interesting spectral behaviour. If only I had opted for higher magnification! Here is an image taken with an effective spectral resolution of about 2 angstroms. A coronal loop is evident along with a higher lying wispy structure.
Ha_proms_spectral_series_integrated_mod_siz.png
Ha_proms_spectral_series_integrated_mod_siz.png (45.96 KiB) Viewed 251 times
These features were captured by a number of observers on this forum:
Eric Roel viewtopic.php?f=4&t=28475
Phil (Astrophil) viewtopic.php?f=4&t=28464
John (highfnum) viewtopic.php?f=4&t=28474
James (DeepSolar64) viewtopic.php?f=4&t=28473.

The spectroheliograph revealed that the prominence consisted of structures that varied significantly with wavelength. In order to demonstrate this, I assembled the following animated spectral sequence of the prominence: a movie showing the shape of the prominence as the wavelength is tuned over a range of about 2.5 angstroms.
Ha_proms_spectral_series.gif
Ha_proms_spectral_series.gif (1.49 MiB) Viewed 251 times
Each frame of the video represents a step of 0.058 angstroms, or, in terms of the recessional velocity corresponding to a 0.058 angstrom doppler shift, a velocity step of 2.56 km/s. The frames in the animation are labelled with the recessional velocity with respect to gas at rest on the disk surface. Negative velocities refer to approaching gas while positive numbers refer to receding gas. It looks as if the wispy prom component had a significant recessional velocity component. Was this gas in the process of being ejected?

Anyway, it's good to be making spectroheliograms again! Hope you enjoy.

Cheers.
Peter



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Re: 12 June 2020 Spectroheliograms

Post by Carbon60 » Sat Jun 27, 2020 7:32 am

Peter, these are exceptionally good spectroheliograms. The quality is amazing.

The prom animation is absolutely fascinating and it would also be interesting to see these images stacked in colour, 'blue to red' to show in one image the entire prom and its velocity field.

Excellent.

Stu.


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Re: 12 June 2020 Spectroheliograms

Post by Montana » Sat Jun 27, 2020 8:23 am

Absolutely wonderful Peter, a thoroughly enjoyable and informative post, the animation is incredible together with marvellous views of the sun. I do like the He D3 how it is completely inverted to Halpha or CaK view

:bow :bow :bow

Alexandra



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Re: 12 June 2020 Spectroheliograms

Post by marktownley » Sat Jun 27, 2020 8:43 am

Fascinating post and excellent images Peter! Love it!


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Re: 12 June 2020 Spectroheliograms

Post by JochenM » Sat Jun 27, 2020 9:54 am

Very interesting to see/read Peter. Nice work.



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Re: 12 June 2020 Spectroheliograms

Post by highfnum » Mon Jun 29, 2020 12:21 am

when it comes to this
you are truly
"Peter The Great"



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Re: 12 June 2020 Spectroheliograms

Post by p_zetner » Tue Jun 30, 2020 2:44 am

Thanks for the comments, everyone (and the SPOD!).

Stu: Your idea of stacking these images as individually coloured frames is a good one. I'm not sure how to interpret the colour mixing that would result though. It seems to me the colour associated with some particular frame (and the associated velocity) would be lost in the mixing. I have to give this more thought. I have written a routine to calculate the doppler shift associated with an individual pixel in an image (using the spectrum associated with that pixel) and will experiment with this a bit more. In the meantime, here are some dopplergrams for this particular prominence. Orange (blue) regions correspond to receding (approaching) gas moving at, roughly, the velocities (km/s) indicated by the numeric labels. This gives an idea of which portions of the prominence are moving in what line-of-sight direction and at what speed (with respect to stationary gas at solar disk centre). The high-altitude, wispy portion of the prom and the coronal loop seem to clearly display opposite and fairly substantial line-of-sight velocities.

Cheers.
Peter
dopplergrams_montage_v2_lbls.png
dopplergrams_montage_v2_lbls.png (354.37 KiB) Viewed 171 times



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Re: 12 June 2020 Spectroheliograms

Post by Montana » Tue Jun 30, 2020 9:22 am

I really like that Peter!!

Alexandra



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Re: 12 June 2020 Spectroheliograms

Post by christian viladrich » Thu Jul 02, 2020 3:20 pm

These spectroheliograms are facinating ! Thanks for sharing.
Le CN line is interesting. We don't see a lot of CN images.


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Re: 12 June 2020 Spectroheliograms

Post by Phil Rousselle » Fri Jul 03, 2020 8:35 am

very nice spectroheliograms. excellent !
Phil



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