Found the next challenge! CN wavelength

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Found the next challenge! CN wavelength

Post by Merlin66 »

While researching on magnetometers (June 1972 issue of Sky&Telescope) I found the "Babinet compensator" they used cost thousands $$$$$$.
Andre Rondi has achieved creditable results with basic 1/4 wave plates on his SHG, which I'm sure cost MUCH less!!
http://www.astrosurf.com/rondi/obs/shg/ ... nglais.htm

What caught my eye was a SHG solar image taken in the light of the molecular Cyanogen.
This records in the photosphere/ chromosphere interface and to quote "A significant observational advance occurred when Sheeley discovered that a spectroheliogram taken in the head band of cyanogen (3883.4 A) mapped the (magnetic) fields just as well as a Zeeman picture. Only the polarity information was missing....(these) pictures could be made more rapidly than the Zeeman films, better resolution was achieved."

I haven't been able to find any other solar CN images...this one was taken 50 years ago (July 4, 1970) That's my next challenge!!!
CN_3883A_June1972 S&T.jpg
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Re: Found the next challenge! CN wavelength

Post by marktownley »

Looking forward to seeing the results Ken ;)


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Re: Found the next challenge! CN wavelength

Post by Carbon60 »

Always nice to have a challenge :)

It will be interesting to follow your progress.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Found the next challenge! CN wavelength

Post by Merlin66 »

Managed to get a better image in Mg(b2) which allowed comparison with a Ca II K image and my latest challenge the CN molecular line "head" at 3883A.
It looks like the Mg is very close to white light (photosphere) then the CN and finally the CaK in the lower chromosphere.

Note the filaments in CaK (and the proms)
MiniSHG on the ED80. (Some artefacts to be fixed on the CN line - not an easy target.)
Mg (b2)
Mg (b2)
103703_Mg.jpg (153.79 KiB) Viewed 1703 times
Close up AR 2929
Close up AR 2929
103703_crop02Mg.jpg (361.65 KiB) Viewed 1703 times
CN (3883) molecular band
CN (3883) molecular band
114545_02_CN.jpg (52.92 KiB) Viewed 1703 times
Ca II K
Ca II K
112503_CaK.jpg (202.93 KiB) Viewed 1703 times
Ca II K proms
Ca II K proms
112503_CaK_protus.jpg (166.79 KiB) Viewed 1703 times


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Re: Found the next challenge! CN wavelength

Post by KMH »

That's really interesting. I have to admit it never occurred to me that molecular species would be present at the photo/chromo interface. But a quick google shows the CN heat of formation is about 101 kcal/mole, which (says google) equates to about 50000 K temperature. Great images!

Kevin


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Re: Found the next challenge! CN wavelength

Post by marktownley »

Interesting Ken and very nicely captured. CN looks similar to CaH and Mg,


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Re: Found the next challenge! CN wavelength

Post by Merlin66 »

The professionals say the CN reflects the active magnetic regions and hence different from the other wavelengths.


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Re: Found the next challenge! CN wavelength

Post by p_zetner »

Ken, here’s a link to an example CN image I took several years ago.

https://solarchatforum.com/viewtopic.php?t=18063

The CN band is useful in the same way a G-band (CH molecule) image is useful. High spatial resolution images in CN reveal chromospheric bright points which are visible with a factor of 3 more contrast than those same bright points in a G-band image. These bright points are associated with intense magnetic fields concentrated into small regions. The CN image at larger image scales reveals magnetic fields only in the sense that the solar faculae are visible with high contrast and the faculae are associated with fields. I wouldn’t really like to make the claim that a CN image is equivalent to an unpolarized magnetogram, unless you want to extend that claim to all images in which faculae are visible!

Cheers.
Peter
Last edited by p_zetner on Sat Jan 29, 2022 12:11 am, edited 1 time in total.


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Re: Found the next challenge! CN wavelength

Post by p_zetner »

Here’s a reference:

A&A 462, 1157-1163 (2007)
Narrow-band imaging in the CN band at 388.33 nm
H. Uitenbroek and A. Tritschler

https://www.aanda.org/articles/aa/abs/ ... 86-06.html


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Re: Found the next challenge! CN wavelength

Post by Merlin66 »

Peter,
Thanks for the additional references.
The use of an old Lyot filter shows similarities to the narrowband MiniSHG results.


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Re: Found the next challenge! CN wavelength

Post by p_zetner »

Here are some additional references and another (not particularly great) CN image I took in 2017:

https://solarchatforum.com/viewtopic.php?f=8&t=23945

Comparison with Ca K shows the difference between photospheric and chromospheric features as well as the correlation in location of faculae (CN) with plage (Ca K). This is explored further in Paper 1 below.

References:

Paper 1.
Title: New Observations of Solar Magnetic and Brightness Fields
Authors: Sheeley, N. R., Jr. & Liu, S. Y.
Journal: Line Formation in the Presence of Magnetic Fields, Manuscripts presented at a conference held in Boulder, Colorado, 20 August - 2 September, 1971. Boulder, CO: National Center for Atmospheric Research, 1972., p.285
https://adsabs.harvard.edu/full/1972lfpm.conf..285S


Paper 2.
Title: The Evolution of the Photospheric Network
Authors: Sheeley, N. R., Jr.
Journal: Solar Physics, Volume 9, Issue 2, pp.347-357
https://adsabs.harvard.edu/full/1969SoPh....9..347S


Cheers.
Peter


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Re: Found the next challenge! CN wavelength

Post by christian viladrich »

Hello,
Sunrise balloon 1-meter solar telescope did a lot of imaging in near-UV including CN line.
https://www.mps.mpg.de/solar-physics/sunrise-telescope
Unfortunatly, the images they took are difficult to find. I found some in a PhD thesis by Tino Riethmüller, "Investigations of small-scale magnetic features on the solar surface".

Hinode satellite also took a lot of CN images.

As said by Peter, CN images are somewhat equivalent to G-band images, with more contrast, but with much worse seeing effect. Maybe I'll try someday with the 300 mm Newtonia. I am not very far from it with my 396-5 nm filter.


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Re: Found the next challenge! CN wavelength

Post by p_zetner »

christian viladrich wrote: Sat Jan 29, 2022 9:00 pm Maybe I'll try someday with the 300 mm Newtonia. I am not very far from it with my 396-5 nm filter.
Hi Christian.
You might be interested in the attached table comparing bright point contrast in G-Band and CN (band head) images for various filter bandpasses. It’s from the reference:

A&A 462, 1157-1163 (2007)
Narrow-band imaging in the CN band at 388.33 nm
H. Uitenbroek and A. Tritschler

(Link above.)

Cheers.
Peter
50A91113-DD39-4528-974F-DEB038AC7F65.jpeg
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Re: Found the next challenge! CN wavelength

Post by Merlin66 »

Peter,
Thanks.
I'd already found the Sheeley references.
There are very few CN band images around for comparison.


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Re: Found the next challenge! CN wavelength

Post by christian viladrich »

p_zetner wrote: Sat Jan 29, 2022 10:54 pm Hi Christian.
You might be interested in the attached table comparing bright point contrast in G-Band and CN (band head) images for various filter bandpasses. It’s from the reference:

A&A 462, 1157-1163 (2007)
Narrow-band imaging in the CN band at 388.33 nm
H. Uitenbroek and A. Tritschler
Thanks Peter. They give equivalent contrast between CN and G-band for 1 A filters. My filter is unfortunately closer to nm than A.
We need a Lyot filter there, or a spectrograph.
Cheers


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Re: Found the next challenge! CN wavelength

Post by marktownley »

Informative thread, thanks all!


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