1.5 A Alluxa Ca K first light images - July 12 and 13

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christian viladrich
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1.5 A Alluxa Ca K first light images - July 12 and 13

Post by christian viladrich »

Hi,

I recently bought a 1.5 A Alluxa Ca K filter.

Extensive testing with Sol'Ex spectro is presented here :
viewtopic.php?t=37280

Seeing conditions were not very good due to the heat wave in France. But here are some first images taken on July 12 and 13 :

http://astrosurf.com/viladrich/astro/so ... SI1600.jpg
CaK-12July2022-9h40UT-Alluxa037nm-1A-ASI1600.jpg
CaK-12July2022-9h40UT-Alluxa037nm-1A-ASI1600.jpg (4.94 MiB) Viewed 745 times
http://astrosurf.com/viladrich/astro/so ... SI1600.jpg
Ca K-13July2022-8h31UT-TOA150-Alluxa-0.37nm-1.5nm-ASI1600.jpg
Ca K-13July2022-8h31UT-TOA150-Alluxa-0.37nm-1.5nm-ASI1600.jpg (5.01 MiB) Viewed 745 times
The chromospheric fringe :
http://astrosurf.com/viladrich/astro/so ... 00-ddp.jpg
Ca K-13July2022-8h31UT-TOA150-Alluxa-0.37nm-1.5nm-ASI1600-ddp.jpg
Ca K-13July2022-8h31UT-TOA150-Alluxa-0.37nm-1.5nm-ASI1600-ddp.jpg (3.66 MiB) Viewed 745 times
A close-up on the largest group, at +0.3 A of the center of Ca K :
http://astrosurf.com/viladrich/astro/so ... ASI290.jpg
AR3055-13July2022-8h57UT-TOA150-Alluxa037-15A-ASI290.jpg
AR3055-13July2022-8h57UT-TOA150-Alluxa037-15A-ASI290.jpg (1.13 MiB) Viewed 745 times
and at +0.1 A of the centre of Ca K :
http://astrosurf.com/viladrich/astro/so ... ASI290.jpg
AR3055-13July2022-10h15UT-TOA150-Alluxa037nm-15A-tuned-ASI290.jpg
AR3055-13July2022-10h15UT-TOA150-Alluxa037nm-15A-tuned-ASI290.jpg (899.28 KiB) Viewed 745 times
The difference between these two last images is quite small, but we can seen that the ombrae are a bit larger at +0.1 A, the reverse granulation is a bit softer, and some low contrast fibrils are visible between the sunspots.

Clear skies

Christian


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by ffellah »

Hi Christian: the full disks are great but the close ups of the sunspots are STUNNING !

:bow

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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by marktownley »

These are very impressive Christian. I need to look at these a little more carefully on a bigger screen rather than on my phone.


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by nicspenceryork »

Wow! The detail is unbelievably good.
Really enjoyed studying them, thanks,
Nic


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by christian viladrich »

Thanks guys !

BTW, there is a very faint filament visible in the FD images. It is between the two groups a bit above the center of the disk.
I saw it on the computer screen during acqusition. It was confirmed with SHG observations made at the same time.
But ... I can't find any way to make it more visible on processed images :-(


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by ffellah »

Christian: what was the site these images were taken from ?

Franco


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by christian viladrich »

ffellah wrote: Mon Jul 25, 2022 7:44 pm Christian: what was the site these images were taken from ?

Franco
Hello Franco,
These were taken from home (300 mm altitude). It was rather warm (30°C in shadow), and the seeing was rather bad (in spite of the SSM value).


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by thesmiths »

christian viladrich wrote: Mon Jul 25, 2022 7:43 pm BTW, there is a very faint filament visible in the FD images. It is between the two groups a bit above the center of the disk.
I saw it on the computer screen during acquisition. It was confirmed with SHG observations made at the same time.
Do you think the faintness of the filaments has to do with being "off band"? Your spectral resolution is not that different than my recent SHG imaging with a 1800 l/mm grating, where filaments are quite easily visible (although not a distinct as with a 2400 l/mm grating).

I have seen other CaK filter images (with probably not as narrow a bandwidth as you have) that show filaments and I am thinking that some filters are just by chance tuned closer to the centre of the line.


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by DeepSolar64 »

I ALWAYS enjoy your very professional images Christian.


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by marktownley »

I've embedded the images in the post Christian, hope you don't mind, it makes the comparisons much easier.

The subtle detail differences in the last two images are quite telling.

Have you found any differences in swapping the order of the filters around in the stack?


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by marktownley »

thesmiths wrote: Mon Jul 25, 2022 11:43 pm I have seen other CaK filter images (with probably not as narrow a bandwidth as you have) that show filaments and I am thinking that some filters are just by chance tuned closer to the centre of the line.
I think you are right here Douglas.


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by jp-brahic »

fantastic result Christian !!!

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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by Montana »

Oh my! the last images are to die for, I would give anything to get a picture like this :bow :bow :bow

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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by christian viladrich »

marktownley wrote: Tue Jul 26, 2022 5:59 am I've embedded the images in the post Christian, hope you don't mind, it makes the comparisons much easier.

The subtle detail differences in the last two images are quite telling.

Have you found any differences in swapping the order of the filters around in the stack?
Thanks for embedding the images. For some reasons, it was not successfull on my side.

Swapping the filters has certainly an impact of ghost images. I have more tests to do. Ghost images are also impacted by the distance between filters, and of course filter tilt.
I am also planning to use the AiryLab telecentric in order to have more flexibility in the filter stack. I am a little bit on the high side regarding sampling with the Baader FFC.


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by christian viladrich »

thesmiths wrote: Mon Jul 25, 2022 11:43 pm
christian viladrich wrote: Mon Jul 25, 2022 7:43 pm BTW, there is a very faint filament visible in the FD images. It is between the two groups a bit above the center of the disk.
I saw it on the computer screen during acquisition. It was confirmed with SHG observations made at the same time.
Do you think the faintness of the filaments has to do with being "off band"? Your spectral resolution is not that different than my recent SHG imaging with a 1800 l/mm grating, where filaments are quite easily visible (although not a distinct as with a 2400 l/mm grating).

I have seen other CaK filter images (with probably not as narrow a bandwidth as you have) that show filaments and I am thinking that some filters are just by chance tuned closer to the centre of the line.
This is a very interesting question.

I think part of the answer was given by Peter Zetner in his presentation of the measurement of the temperature of a filament in Solar Astronomy (p 446).
He measured the optical depth of a filament in Ha and in Ca K. He found out that the optical depth in Ha was about 8x larger than the optical depth in Ca K. This important results explain why the filaments should reduced contrast and visibility in Ca K.
Another conclusion was that a filament with a large optical depth is visible over a wider range of wavelengths arround the center line.

It was indeed the case with the filament very faintly visible in my images. On the images taken with Sol'Ex, this filament was nothing special on the center of Ca K. But in the wings of Ca K, this filament was still visible while the other disappeared.

I still have to gather these images in a web page to show this.

So I would say this is not so much about tuning the center line of the filter (still we need to be prety close of the center of Ca K), but more about the optical depth of the filament, which results in a visibility accross a wider wavelength range. Just my current guess about it.

Christian
Last edited by christian viladrich on Tue Jul 26, 2022 12:05 pm, edited 1 time in total.


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by christian viladrich »

BTW, regarding spectral resolution, the SHG vastly outperforms my double stack combination. With Sol'Ex, I can see traces of Ca K2v and K2r, very close to K3. These can be seen as two very small bumps on each side of the center of Ca K line (blue line)

http://astrosurf.com/viladrich/astro/in ... -Graph.jpg

The bandpass of my double-stack combinaision is much larger (red curve) with a lot of transmission off-band.

I don't know what filter combination would be equivalent to a SHG. If we look at Ha images, it seems that triple-stack Ha images are rather close to SHG images.


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by MAURITS »

Exceptional images Christian.


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by rigel123 »

Amazing images as always!


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by thesmiths »

christian viladrich wrote: Tue Jul 26, 2022 8:38 am He measured the optical depth of a filament in Ha and in Ca K. He found out that the optical depth in Ha was about 8x larger in Ha. This important results explain why the filaments should reduced contrast and visibility in Ca K.
I assume you mean "the optical depth in Ha was about 8x larger in Ca K" ?
Last edited by thesmiths on Tue Jul 26, 2022 12:26 pm, edited 1 time in total.


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by christian viladrich »

thesmiths wrote: Tue Jul 26, 2022 11:34 am
christian viladrich wrote: Tue Jul 26, 2022 8:38 am He measured the optical depth of a filament in Ha and in Ca K. He found out that the optical depth in Ha was about 8x larger in Ha. This important results explain why the filaments should reduced contrast and visibility in Ca K.
I assume you mean "the optical depth in Ha was about 8x larger in Ca K" ? If you do an edit on your original text, I will delete this one.
Yes indeed, the optical depth in Ha was about 8x larger than the optical depth in Ca K.
Sorry for the typo. I've just corrected the post accordingly.
Thanks !


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by arnedanielsen »

Absolutely stunning results, Christian!

Best regards,
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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by Carbon60 »

Phenomenal results, Christian.

Stu.


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by cybermayberry »

Absolute eye candy


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Re: 1.5 A Alluxa Ca K first light images - July 12 and 13

Post by LeoD »

Fine work of filters adjustment and the amazing result is worth it!
I've even much more impressed making comparison with my own attempt in Ca K on the same day July 13. Now I see the etalon.
thanks for posting
Leo


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