Mg II in UltraViolet
- Valery
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Mg II in UltraViolet
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
https://www.aanda.org/articles/aa/pdf/2 ... 358-15.pdf
And very interesting reading.
Valery
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Re: Mg II in UltraViolet
Interesting read indeed!
http://brierleyhillsolar.blogspot.co.uk/
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Re: Mg II in UltraViolet
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
But... even a 120mm telescope will have a resolution of 280mm telescope worked at 656nm Ha !!!
Valery
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Re: Mg II in UltraViolet
How feasible is it as a filter?
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Re: Mg II in UltraViolet
We need professional opinion(s).
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Re: Mg II in UltraViolet
What is the QE of our cameras at these wavelengths?
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Re: Mg II in UltraViolet
thanks for this article Valery
JP
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Re: Mg II in UltraViolet
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
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Re: Mg II in UltraViolet
'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.
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Re: Mg II in UltraViolet
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.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.
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.
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Re: Mg II in UltraViolet
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:
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:
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:
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 ;-)
"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:
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:
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:
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 ;-)
Last edited by Bob Yoesle on Wed Nov 07, 2018 6:04 pm, edited 3 times in total.
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Re: Mg II in UltraViolet
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!
Transmission rapidly disappears beyond ~ 320nm.
Cheers.
Peter
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!
Transmission rapidly disappears beyond ~ 320nm.
Cheers.
Peter
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Re: Mg II in UltraViolet
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:
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.
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:
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.
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Re: Mg II in UltraViolet
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 !
:-)
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 !
:-)
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Re: Mg II in UltraViolet
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
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
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Re: Mg II in UltraViolet
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.
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.
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Re: Mg II in UltraViolet
His achievements were high at that time. Now he is working about solar 12" refractor.TheSkyBurner wrote: ↑Thu Nov 08, 2018 6:40 am Would anybody say that this guy, Harald Paleske wasted his money? ?
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Re: Mg II in UltraViolet
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 ;-)
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 ;-)
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Re: Mg II in UltraViolet
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
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
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Re: Mg II in UltraViolet
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...
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...
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Re: Mg II in UltraViolet
Hi Bob,
Is this the C8 or the C8 EdgeHD ?
Is this the C8 or the C8 EdgeHD ?
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Re: Mg II in UltraViolet
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.
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.
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Re: Mg II in UltraViolet
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).
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).
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Re: Mg II in UltraViolet
1. This is the ARIES 12" DERF two bands filterTheSkyBurner 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
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
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Re: Mg II in UltraViolet
Hello Bob,
Here are the simulations for a re-spaced classic C8 :
http://astrosurf.com/viladrich/astro/in ... -Plate.htm
The diffraction limited flat-field increases by a factor of four when the Schmidt plate position is set 230mm ahead its nominal position.
There is no impact on the spherochromatism (= still very bad in near UV).
As for the correction in near UV light, there are several issues :
- the spherical aberration changes rapidely with wavelength below 420 mm. This is why the Strelh ratio drops drastically below 420 mm ;
- in order to design a spherical aberration corrector, we would need to know with good accuracy what is the actual shape of the Schmidt plate ;
- this is why ASH actually measured the Schmidt plate of a C8 to design a Barlow lens for this specific C8.
My guess is that a 200 mm F/8 Newtonian telescope is much more appropriated to high resolution Ca K imaging.
I hope to run some tests in Ha on my 300 mm Newtonian with a sub-aperture ERF. If things go well, the next step will be to make a small aperture Ca K ERF filter.
I still have the option open for a ERM coating on my 300 mm scope. The idea would be to have a coating reflecting red (for Ha) and near UV light (for Ca K).
Here are the simulations for a re-spaced classic C8 :
http://astrosurf.com/viladrich/astro/in ... -Plate.htm
The diffraction limited flat-field increases by a factor of four when the Schmidt plate position is set 230mm ahead its nominal position.
There is no impact on the spherochromatism (= still very bad in near UV).
As for the correction in near UV light, there are several issues :
- the spherical aberration changes rapidely with wavelength below 420 mm. This is why the Strelh ratio drops drastically below 420 mm ;
- in order to design a spherical aberration corrector, we would need to know with good accuracy what is the actual shape of the Schmidt plate ;
- this is why ASH actually measured the Schmidt plate of a C8 to design a Barlow lens for this specific C8.
My guess is that a 200 mm F/8 Newtonian telescope is much more appropriated to high resolution Ca K imaging.
I hope to run some tests in Ha on my 300 mm Newtonian with a sub-aperture ERF. If things go well, the next step will be to make a small aperture Ca K ERF filter.
I still have the option open for a ERM coating on my 300 mm scope. The idea would be to have a coating reflecting red (for Ha) and near UV light (for Ca K).
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Re: Mg II in UltraViolet
In my opinion for hires imaging in the near UV correcting the system for SA is much more important that enlarging the D-L field, thus an all-reflecting system would definitely be much more preferable than modifying a SCT.
BTW, one can consider a commercial Cassegrain, it is a relatively inexpensive scope that can be modified to make it better suited for solar work.
BTW, one can consider a commercial Cassegrain, it is a relatively inexpensive scope that can be modified to make it better suited for solar work.
Raf
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Re: Mg II in UltraViolet
Interesting info Raf :-)
I didn't know they have these small size Cassegrain scopes.They have quartz mirrors which is very nice. I have no idea of the optical quality.
I didn't know they have these small size Cassegrain scopes.They have quartz mirrors which is very nice. I have no idea of the optical quality.
Christian Viladrich
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http://planetary-astronomy.com/
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Re: Mg II in UltraViolet
They also have a 12" classic Cassegrain from Orion Optics UK, although it costs four times as much. 25% obstruction (vs 33% on the smaller ones). Comes with a Ronchi test, but no mention of minimum performance. George
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Re: Mg II in UltraViolet
Hmmm
Once we have solved all these technical difficulties....
What about a camera which can record that far into the UV??????
Once we have solved all these technical difficulties....
What about a camera which can record that far into the UV??????
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Re: Mg II in UltraViolet
" Here are the simulations for a re-spaced classic C8 :
http://astrosurf.com/viladrich/astro/in ... -Plate.htm "
Thanks so much for this Christian!
http://astrosurf.com/viladrich/astro/in ... -Plate.htm "
Thanks so much for this Christian!
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Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
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