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Mg II in UltraViolet

Posted: Wed Oct 31, 2018 4:30 am
by Valery
See what can be imaged in near UV light at Mg II line.

https://www.aanda.org/articles/aa/pdf/2 ... 358-15.pdf

And very interesting reading.


Valery

Re: Mg II in UltraViolet

Posted: Wed Oct 31, 2018 9:57 am
by Montana
Thanks for the read Valery

Alexandra

Re: Mg II in UltraViolet

Posted: Thu Nov 01, 2018 9:48 am
by marktownley
Interesting read indeed!

Re: Mg II in UltraViolet

Posted: Thu Nov 01, 2018 11:13 am
by Valery
Note, folks, that even with large(!) CWL shift the picture remains VERY different to what can be seen in a continuum and this makes me optimistic that even 1A two cavity filter will deliver unusual picture full of quite different details. The only problem is do we have such a UV sensitive CCD or CMOS cameras with high speed?

But... even a 120mm telescope will have a resolution of 280mm telescope worked at 656nm Ha !!!

Valery

Re: Mg II in UltraViolet

Posted: Fri Nov 02, 2018 1:46 pm
by marktownley
How feasible is it as a filter?

Re: Mg II in UltraViolet

Posted: Fri Nov 02, 2018 4:55 pm
by Valery
marktownley wrote:
Fri Nov 02, 2018 1:46 pm
How feasible is it as a filter?
We need professional opinion(s).

Re: Mg II in UltraViolet

Posted: Sat Nov 03, 2018 4:55 pm
by marktownley
What is the QE of our cameras at these wavelengths?

Re: Mg II in UltraViolet

Posted: Tue Nov 06, 2018 10:59 am
by jp-brahic
thanks for this article Valery :)

JP

Re: Mg II in UltraViolet

Posted: Tue Nov 06, 2018 4:07 pm
by Valery
marktownley wrote:
Sat Nov 03, 2018 4:55 pm
What is the QE of our cameras at these wavelengths?
I don't know. But possibly high enough. All in all UV is much more powerful than IR radiation.

But they may be expensive.


Valery

Re: Mg II in UltraViolet

Posted: Tue Nov 06, 2018 6:23 pm
by marktownley
'Off the Shelf' UV achromats aren't ideal, but could form a starting point for such a scope. You could make a tiny full disk instrument; the 50/200 https://www.edmundoptics.eu/f/near-uv-n ... ses/13900/ could replace the objective in a finder scope, and then mount the filters on the nose of a camera. Would be easy to make up a barlow https://www.edmundoptics.eu/f/UV-Fused- ... ses/12414/ to increase image scale for small pixel camera. Not perfect but could give a cheap indication of success for the idea. Good sky transparency and altitude would increase success.

Re: Mg II in UltraViolet

Posted: Wed Nov 07, 2018 5:19 am
by Valery
marktownley wrote:
Tue Nov 06, 2018 6:23 pm
'Off the Shelf' UV achromats aren't ideal, but could form a starting point for such a scope. You could make a tiny full disk instrument; the 50/200 https://www.edmundoptics.eu/f/near-uv-n ... ses/13900/ could replace the objective in a finder scope, and then mount the filters on the nose of a camera. Would be easy to make up a barlow https://www.edmundoptics.eu/f/UV-Fused- ... ses/12414/ to increase image scale for small pixel camera. Not perfect but could give a cheap indication of success for the idea. Good sky transparency and altitude would increase success.
If one will go this way, he should not save money on a too small telescope. 100mm is a minimal size I would say. Minimal SA is a must for such a telescope. A must have also a SSM.
The main price driving factor is an etalon with a 0,5A bandwidth. Give me such an etalon and I will make a telescope without any real problem.

Re: Mg II in UltraViolet

Posted: Wed Nov 07, 2018 4:15 pm
by Bob Yoesle
An interesting research paper - thanks for sharing it Valery.

"If one will go this way, he should not save money on a too small telescope. 100mm is a minimal size I would say. Minimal SA is a must for such a telescope. A must have also a SSM. The main price driving factor is an etalon with a 0,5A bandwidth. Give me such an etalon and I will make a telescope without any real problem. "

"The only problem is do we have such a UV sensitive CCD or CMOS cameras with high speed?"

For me a bigger problem would be how well any COTS telescope would perform at this wavelength (280 nm). The only telescope that might do a passable if not good job is the Takahashi TOA 130:

TOA 150 Long CA.jpg
TOA 150 Long CA.jpg (41.82 KiB) Viewed 564 times

A substantial investment in its own right:


http://www.takahashiamerica.com/takahas ... actor.html


I doubt Takahashi knows how well the TOA 130 optics perform at 280 nm, nor do they probably care, so you'll have to buy one to find out.

The MG II on-band images look very similar to H alpha, and for Ellerman Bombs, off-band Ha (and CaK) might be just as suitable:

fg1.h.jpg
fg1.h.jpg (283.97 KiB) Viewed 564 times
Alexandra's CaK Ellerman Bomb series.jpg
Alexandra's CaK Ellerman Bomb series.jpg (196.64 KiB) Viewed 564 times

So what this would actually entail is a very expensive niche filter, for which you would have to have a very expensive telescope optic (if not using a reflector with appropriate ancillary lenses), and an as yet unknown sensitivity CCD/CMOS camera, and so forth.

Honestly, given my already considerable investment in H alpha and CaK, I think I'll pass. In fact, I'd rather put my money towards a dual or tri-band band C8 ERF scope, and a solution for solving the SCA of the C8 at 393 nm so that it could better be used for CaK work:

C8 optical graphs.jpg
C8 optical graphs.jpg (163.21 KiB) Viewed 564 times

Fix that and I'm all in!

Therefore I'll probably leave the the Mg II line for solar researchers who will do more than just take pretty pictures... not that pretty pictures aren't fun to look at - I've taken a few of them myself ;-)

Re: Mg II in UltraViolet

Posted: Wed Nov 07, 2018 4:52 pm
by p_zetner
Well argued, Bob.

If I could add to this discussion, I would address an even bigger elephant in the room: atmospheric transmission at 280nm.
Here are atmospheric transmission curves at the Paranal VLT site. Paranal is located in the Atacama Desert of northern Chile on Cerro Paranal at 2,635 m altitude!
IMG_2843.jpg
IMG_2843.jpg (352.58 KiB) Viewed 556 times
Transmission rapidly disappears beyond ~ 320nm.

Cheers.
Peter

Re: Mg II in UltraViolet

Posted: Wed Nov 07, 2018 5:13 pm
by Bob Yoesle
Thanks for that Peter ;-)

OK, so now we add a sounding rocket to the equipment list:

https://www.youtube.com/watch?v=sQw_C5KLhFM

Alternatively, one could always move to Antarctica:

Solar-Spectrum-GballEditz.png
Solar-Spectrum-GballEditz.png (99.12 KiB) Viewed 547 times


https://www.youtube.com/watch?v=fzN0LbZ ... e=youtu.be


But you'll probably also need a new wardrobe for keeping warm... and dew heaters.

Re: Mg II in UltraViolet

Posted: Wed Nov 07, 2018 6:03 pm
by p_zetner
Thanks, Bob.

I like the idea of a visit to Antarctica. Living in central Canada with some harsh winter weather, I’m pretty much set for clothing. Can’t forget to slather on the sunscreen with the enhanced UVC !

:-)

Re: Mg II in UltraViolet

Posted: Wed Nov 07, 2018 6:12 pm
by Valery
Hi Bob,

Here is the CaK image of the sun active area #12715 taken with 11" SCT. So, I see no problems at all for for a C8. And you can get a DERF filter soon after the order.


Valery

Re: Mg II in UltraViolet

Posted: Wed Nov 07, 2018 11:39 pm
by Merlin66
I use various telescopes , including the ol' Genesis for spectroscopy with commercial CCD's.
My experience is that the available CCD's have little or no response below 360nm.
The Strehl ratio for the Genesis at around 370nm seems acceptable, giving a good workable stellar image.
I use the ATiK 314L camera most of the time......
This is the UV spectrum of Sirius taken with the above gear.
sirius_blue.jpg
sirius_blue.jpg (48.81 KiB) Viewed 516 times

Re: Mg II in UltraViolet

Posted: Thu Nov 08, 2018 9:22 am
by Valery
TheSkyBurner wrote:
Thu Nov 08, 2018 6:40 am
Would anybody say that this guy, Harald Paleske wasted his money? ?
His achievements were high at that time. Now he is working about solar 12" refractor.

Re: Mg II in UltraViolet

Posted: Thu Nov 08, 2018 4:47 pm
by Bob Yoesle
Hi Valery,

Do you have a transmission plot for the C8 DERF? I also would like to know the physical dimensions, and if it is possible to put a central hole in the filter. I'm considering a re-spaced SCT mod and would prefer to mount the secondary mirror to the DERF if it could be made to replace the corrector...

Your C11 images are very good. but they might be even better with a dedicated 393 nm CSA corrector - seems like it would be doable... you never know for sure until you try ;-)

Re: Mg II in UltraViolet

Posted: Thu Nov 08, 2018 8:08 pm
by christian viladrich
Hi Bob,
I have done some simulations there for a re-spaced C14 :
http://astrosurf.com/viladrich/astro/in ... -Plate.htm
I can run some more for the C8 if it is helpfull.
Christian

Re: Mg II in UltraViolet

Posted: Fri Nov 09, 2018 4:50 am
by Bob Yoesle
Hi Christian,

Thanks you very much - that would be wonderful :-) I have seen your C14 re-spaced write up and have purchased a carbon fiber tube towards the implementation...

Re: Mg II in UltraViolet

Posted: Fri Nov 09, 2018 7:46 pm
by christian viladrich
Hi Bob,
Is this the C8 or the C8 EdgeHD ?

Re: Mg II in UltraViolet

Posted: Sat Nov 10, 2018 12:27 am
by Bob Yoesle
Hi Christian,

It's the standard (not the Edge-HD) C8.

Any chance you could "cook up" a spherical aberration corrector using COTS fused silica len(es) from Edmund, Thor Labs, etc? That seems like it would be an ideal CaK imaging platform and relatively less expensive compared to a custom CaK refractor. I would also possibly be placing the corrector just ahead of a Baader 3x telecentric lens system and CaK module.

Re: Mg II in UltraViolet

Posted: Sat Nov 10, 2018 2:35 pm
by Bob Yoesle
Without the optical prescriptions of the lens system, it is impossible to know.

The respaced SCT corrector probably does a better job of coma reduction, while I believe a separate system would be required for chromatic spherical aberration correction at 393 nm. For CaK work, the PST filters will be OK at f10, but the the Chromatech filter would likely work better with something like the Badder 3x research telecentric which is stated to be well corrected for 393 nm (in addition to being ideal for H alpha).

Re: Mg II in UltraViolet

Posted: Sun Nov 11, 2018 7:32 am
by Valery
TheSkyBurner wrote:
Fri Nov 09, 2018 4:52 am


Jp Brahic's scope seems to be the route to take :) You could easily move the corrector plate if you convert the SCT into a truss ( i guess that would make it an R/C scope because you could fix the primary. If this corrector plate hacking solution is viable to get .95 strehl at 393nm I would immediately jump in to the mirror boat. Carbon fiber might not be suitable because of the heat issues, those tubes are dark as night.

For now, refactors are my solar idol because the increase in cost is exponential with that full size D-erf, Especially on those 350mm mirrors........ Looking at $15,000 without a mount, and without the etalon. Jp. must have a great job !:)
He personally told me that he has purchased a .3A solar spectrum filter and will soon be in solar nirvana .

893ACE07-29CC-40D7-B5F2-6FAD4F466223-561-0000006C4252E79E.JPEG
1. This is the ARIES 12" DERF two bands filter
2. We sell it 2x less than $15000
3. Jean Pierre's Solar Spectrum 1.5 filter is actually 0.25A

Here is the image with a similar 12" filter I took last summer June 19. We now know what kind of images (I hope for better) we can expect from 12" size instruments. Know well Jean Pierre's skill and his seeing conditions we should expect that he will rise the bar higher.


Valery