New CaK etalons from Solar Spectrum

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New CaK etalons from Solar Spectrum

Post by Bob Yoesle »

It's now official.

Solar Spectrum has announced the availability of CaK etalon filter systems with FWHM's less than 1 Angstrom.

K Line Solar Spectrum SM.png
K Line Solar Spectrum SM.png (170.85 KiB) Viewed 4184 times
Solar Spectrum.


Due to the limitations of even the most modern interference filter hard-layer depositing, reliable CWL uniformity and bandpasses below 1.5 A have been essentially unobtainable, and just as with H alpha, CaK etalons offer the only filter technology that can reliably achieve sub-angstrom performance and high angular resolution.

While there is the availability of DayStar K line etalons, like the rest of DayStar's current offerings, the Quarks seem problematic as far as CWL and uniformity, and their better quality CaK Quantums are insanely priced: ~$18,000 USD for a 2.0 A FWHM. :shock:

While I don't know the exact prices, Mark said his CaK filters will be similarly priced to his H alpha offerings, which in reality makes him the only affordable source for a quality < 1 A CaK optical filter system.

Mine's ordered :D

Bob


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Re: New CaK etalons from Solar Spectrum

Post by marktownley »

That's exciting! I hope he has a lot of them :D


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Re: New CaK etalons from Solar Spectrum

Post by christian viladrich »

Exciting news Bob !

I wonder what is the peak transmission of these filters. Do you have any data on this ?


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Re: New CaK etalons from Solar Spectrum

Post by Bob Yoesle »

Hi Christian,

I'll have to make an inquiry with Mark, not sure he has a cleaved piece of mica yet. It will be an ~ 0.5 A RG18 etalon in a Housing I have left over from a previous 2 A DayStar CaK T Scanner (and possibly heated if not TEC controlled). It has hard coated blockers from Alluxa.

I'll post an answer when I hear back.


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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

marktownley wrote: Wed Jan 03, 2024 3:53 pm That's exciting! I hope he has a lot of them :D
While I don’t know how many systems he has on hand I know he sourced a few different sized blocking filters for future orders. With Mark, you have to be patient. I have been waiting for over a year (now that he has sourced a lot of the materials wait time should be shorter) and emails are not answered right away but I know it’s going to be a quality product and the price is reasonable.


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Solar Equipment: Solar Spectrum RG-18 0.3A, Coronado Solarmax 90mm etalon Isle of Man SN-001, Tuscon SN-380 and Meade SM2, Lunt LS80 DS, Quark Chromosphere, Lunt 2" wedge, 2-Lunt CaK II 1200, Baader 3.8 and 5.0 solar film in 208mm cells, and 3D printed Sol'Ex SHG, Lunt 40mm
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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

Interesting. Hopefully the design is done in mind for 100% imaging and according light throughput for the blockers and polarizers. Otherwise im out.


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WL: Antlia 500nm/ 3nm, 393 nm/ 3nm

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Re: New CaK etalons from Solar Spectrum

Post by Bob Yoesle »

Hi Dennis,

I'm confused by the statement "hopefully the design is done in mind for 100% imaging." Do you mean as opposed to visual? Camera sensors are generally much more sensitive than retinas with yellowed eyeball lenses, so that would seem to imply you want less throughput for the blockers and polarizers.

However, these filters incorporate new hard-coated Alluxa blockers with a very high ~ 80% transmission. Additionally, Mark has received some very transparent uncolored mica that makes - in combination with the high T blockers - the less than 1 Angstrom bandpasses practical.

My original DayStar ATM 0.7 A filter from 1976 had such a muscovite mica, and the view was brighter and more uniform than almost any I viewed through since. I really regret having sold it. That's why I'm getting one of these etalons now before that mica becomes less available via incorporation into the Baader / Solar Spectrum H alpha filters. Who knows when more of this high-quality mica will become available again. None will likely be coming out of Russia for quite some time, and that coming out from India and elsewhere is reportedly hit or miss.

Bob


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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

Bob Yoesle wrote: Thu Jan 04, 2024 6:58 pm Hi Dennis,

I'm confused by the statement "hopefully the design is done in mind for 100% imaging." Do you mean as opposed to visual? Camera sensors are generally much more sensitive than retinas with yellowed eyeball lenses, so that would seem to imply you want less throughput for the blockers and polarizers.

However, these filters incorporate new hard-coated Alluxa blockers with a very high ~ 80% transmission. Additionally, Mark has received some very transparent uncolored mica that makes - in combination with the high T blockers - the less than 1 Angstrom bandpasses practical.

My original DayStar ATM 0.7 A filter from 1976 had such a muscovite mica, and the view was brighter and more uniform than almost any I viewed through since. I really regret having sold it. That's why I'm getting one of these etalons now before that mica becomes less available via incorporation into the Baader / Solar Spectrum H alpha filters. Who knows when more of this high-quality mica will become available again. None will likely be coming out of Russia for quite some time, and that coming out from India and elsewhere is reportedly hit or miss.

Bob

Hi Bob,

what i meant was that i hope that the transmission of the system is as high as possible and not compromized (by design) for to make it safe for visual use.
80% for the blockers sounds already very good. Info about the aproximate absolute system transmission will be of help to determine exposure times / signal strength for imaging purposes. Yes, the camera sensors are more sensitive then the human eye, but it doesnt tell me if i can saturate the pixel full well of a certain sensor in a good time.

Apart of this i think this is exciting news and im sure it will be a fine product.

Dennis
Last edited by Dennis on Fri Jan 05, 2024 12:46 pm, edited 1 time in total.


Triband C9.25

H-a: 2x Lunt40 rear mounted

WL: Antlia 500nm/ 3nm, 393 nm/ 3nm

Ca-K: homebrew (includes 2x 1.5A filters, thanks Apollo), corrective lenses (thanks again Apollo)

Cameras: imx432 + imx462
Barlows:
-2x Gerd Düring 2.7x
-2x TMB 1.8x
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Re: New CaK etalons from Solar Spectrum

Post by Ljungmann »

I can confirm the very high transmission in my 0.3Å SS filter. Amazing views! My old Del Woods 0.6Å ATM filter (Quantum house now) has an extremely high transmission. Probably a good old high quality clear/light Muscovite. If I compare a newer SE 0.4Å filter and my 0.3Å filter, The SE filter have a low and "boring" transmission. Looks like 50% of the transmission of my SS filter. Looking forward to the new CaK filters.


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Re: New CaK etalons from Solar Spectrum

Post by Bob Yoesle »

I wonder what is the peak transmission of these filters. Do you have any data on this ?
Hi Christian,

Per Mark:

"The ones we checked went from 15% to 5% . This was caused by the difference in shade of the mica. With all mica, the darker it is the lower T and broader Hw with the same coating design. With the high T blockers, I'm thinking there won't be that much difference in transmission than a Ha filter. Outside from the fact that we can't see k-line. So visibly, it may seem dimmer... We are using a UV Polaroid with a wave plate to make a circular Polaroid. So that's the same as an Ha filter."


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Re: New CaK etalons from Solar Spectrum

Post by galaxie427 »

Bob Yoesle wrote: Thu Jan 04, 2024 6:58 pm However, these filters incorporate new hard-coated Alluxa blockers with a very high ~ 80% transmission. Additionally, Mark has received some very transparent uncolored mica that makes - in combination with the high T blockers - the less than 1 Angstrom bandpasses practical.

My original DayStar ATM 0.7 A filter from 1976 had such a muscovite mica, and the view was brighter and more uniform than almost any I viewed through since. I really regret having sold it. That's why I'm getting one of these etalons now before that mica becomes less available via incorporation into the Baader / Solar Spectrum H alpha filters. Who knows when more of this high-quality mica will become available again. None will likely be coming out of Russia for quite some time, and that coming out from India and elsewhere is reportedly hit or miss.

Bob
Thanks Bob for posting this new offering from Mark Wagner and I just want to say that the above insights you shared are also much appreciated.
I'm glad I saw your post since I was considering Mark's CaK filters a while back and now must move forward. :D

Thanks again,
Luka


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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

5%-15% is a good value, thx for the info.


Triband C9.25

H-a: 2x Lunt40 rear mounted

WL: Antlia 500nm/ 3nm, 393 nm/ 3nm

Ca-K: homebrew (includes 2x 1.5A filters, thanks Apollo), corrective lenses (thanks again Apollo)

Cameras: imx432 + imx462
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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

Just got an update from Mark, my filter is complete and awaiting testing. Of course, he is dealing with lots of rain. My weather hasn’t been favorable either but spring is coming! I have fingers crossed to have it by the end of the month. :D


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Solar Equipment: Solar Spectrum RG-18 0.3A, Coronado Solarmax 90mm etalon Isle of Man SN-001, Tuscon SN-380 and Meade SM2, Lunt LS80 DS, Quark Chromosphere, Lunt 2" wedge, 2-Lunt CaK II 1200, Baader 3.8 and 5.0 solar film in 208mm cells, and 3D printed Sol'Ex SHG, Lunt 40mm
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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

hopskipson wrote: Fri Feb 09, 2024 6:58 pm Just got an update from Mark, my filter is complete and awaiting testing. Of course, he is dealing with lots of rain. My weather hasn’t been favorable either but spring is coming! I have fingers crossed to have it by the end of the month. :D
Lucky you, i didnt even get a reply to my email 4 weeks ago, asking how much one would be :lol:


Triband C9.25

H-a: 2x Lunt40 rear mounted

WL: Antlia 500nm/ 3nm, 393 nm/ 3nm

Ca-K: homebrew (includes 2x 1.5A filters, thanks Apollo), corrective lenses (thanks again Apollo)

Cameras: imx432 + imx462
Barlows:
-2x Gerd Düring 2.7x
-2x TMB 1.8x
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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

Dennis wrote: Fri Feb 09, 2024 8:24 pm
hopskipson wrote: Fri Feb 09, 2024 6:58 pm Just got an update from Mark, my filter is complete and awaiting testing. Of course, he is dealing with lots of rain. My weather hasn’t been favorable either but spring is coming! I have fingers crossed to have it by the end of the month. :D
Lucky you, i didnt even get a reply to my email 4 weeks ago, asking how much one would be :lol:
Hopefully you won’t have to wait over a year for delivery like me. Try to pm him here or send him another email.
According to Mark they will be similarly priced to the RG H-alpha filters but don’t quote me on that.


James
These pretzels are making me thirsty! (C.C.)
The Quark introduced me to this wonderful side of the hobby and the sun hasn’t disappointed yet.
Solar Equipment: Solar Spectrum RG-18 0.3A, Coronado Solarmax 90mm etalon Isle of Man SN-001, Tuscon SN-380 and Meade SM2, Lunt LS80 DS, Quark Chromosphere, Lunt 2" wedge, 2-Lunt CaK II 1200, Baader 3.8 and 5.0 solar film in 208mm cells, and 3D printed Sol'Ex SHG, Lunt 40mm
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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

hopskipson wrote: Fri Feb 09, 2024 10:44 pm
Dennis wrote: Fri Feb 09, 2024 8:24 pm
hopskipson wrote: Fri Feb 09, 2024 6:58 pm Just got an update from Mark, my filter is complete and awaiting testing. Of course, he is dealing with lots of rain. My weather hasn’t been favorable either but spring is coming! I have fingers crossed to have it by the end of the month. :D
Lucky you, i didnt even get a reply to my email 4 weeks ago, asking how much one would be :lol:
Hopefully you won’t have to wait over a year for delivery like me. Try to pm him here or send him another email.
According to Mark they will be similarly priced to the RG H-alpha filters but don’t quote me on that.
well that would be just too long for me : )
i was just curious, so you yourself dont know the price yet for yours?


Triband C9.25

H-a: 2x Lunt40 rear mounted

WL: Antlia 500nm/ 3nm, 393 nm/ 3nm

Ca-K: homebrew (includes 2x 1.5A filters, thanks Apollo), corrective lenses (thanks again Apollo)

Cameras: imx432 + imx462
Barlows:
-2x Gerd Düring 2.7x
-2x TMB 1.8x
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Re: New CaK etalons from Solar Spectrum

Post by DavidP »

You might contact Bob at Alpine Astronomical about availability


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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

DavidP wrote: Mon Feb 12, 2024 3:02 am You might contact Bob at Alpine Astronomical about availability
When I tried to order my H-alpha directly from Mark, he didn’t respond to my email until about a month after I ordered it from Alpine. So it took mark about 6 weeks to respond. The H-alpha took a little over the 12 weeks I was quoted for delivery. The price at that time was $3500 plus $400 for the telecentric and the cost of shipping. It was about a third of what Daystar had listed for a similar filter.


James
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The Quark introduced me to this wonderful side of the hobby and the sun hasn’t disappointed yet.
Solar Equipment: Solar Spectrum RG-18 0.3A, Coronado Solarmax 90mm etalon Isle of Man SN-001, Tuscon SN-380 and Meade SM2, Lunt LS80 DS, Quark Chromosphere, Lunt 2" wedge, 2-Lunt CaK II 1200, Baader 3.8 and 5.0 solar film in 208mm cells, and 3D printed Sol'Ex SHG, Lunt 40mm
Coming Soon: Solar Spectrum CaK II <1A filter
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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

hopskipson wrote: Tue Feb 13, 2024 5:18 pm
DavidP wrote: Mon Feb 12, 2024 3:02 am You might contact Bob at Alpine Astronomical about availability
When I tried to order my H-alpha directly from Mark, he didn’t respond to my email until about a month after I ordered it from Alpine. So it took mark about 6 weeks to respond. The H-alpha took a little over the 12 weeks I was quoted for delivery. The price at that time was $3500 plus $400 for the telecentric and the cost of shipping. It was about a third of what Daystar had listed for a similar filter.

Thanks for the info.


Triband C9.25

H-a: 2x Lunt40 rear mounted

WL: Antlia 500nm/ 3nm, 393 nm/ 3nm

Ca-K: homebrew (includes 2x 1.5A filters, thanks Apollo), corrective lenses (thanks again Apollo)

Cameras: imx432 + imx462
Barlows:
-2x Gerd Düring 2.7x
-2x TMB 1.8x
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Re: New CaK etalons from Solar Spectrum

Post by GeorgeIonas »

Good to hear that Mark as some clear mica. My order for a 0.3 angstrom Ha filter placed through Alpine Astro is coming up to 2 years of wait time.


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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

GeorgeIonas wrote: Sun Feb 18, 2024 8:34 am Good to hear that Mark as some clear mica. My order for a 0.3 angstrom Ha filter placed through Alpine Astro is coming up to 2 years of wait time.
Ouch! That’s a little concerning.


James
These pretzels are making me thirsty! (C.C.)
The Quark introduced me to this wonderful side of the hobby and the sun hasn’t disappointed yet.
Solar Equipment: Solar Spectrum RG-18 0.3A, Coronado Solarmax 90mm etalon Isle of Man SN-001, Tuscon SN-380 and Meade SM2, Lunt LS80 DS, Quark Chromosphere, Lunt 2" wedge, 2-Lunt CaK II 1200, Baader 3.8 and 5.0 solar film in 208mm cells, and 3D printed Sol'Ex SHG, Lunt 40mm
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Re: New CaK etalons from Solar Spectrum

Post by Bob Yoesle »

I know Mark had some production issues with a coating machine needing parts and the like. And he refused to turn out products that ultimately would end up coming right back. Sometimes you just have to bite the bullet and wait - try an Astro-Physics refractor for example, where the wait time is also usually measured in many years. While not perfect, these companies generally emphasize quality vs. quantity.

On the other hand, you can roll the dice on quantity over quality - and may pay the price in the end.


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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

I got a call from Mark today! The filter is ready but his weather has been very bad for testing. So if you know anybody in Chico, please have them dance for sun and stop dancing for rain! 😉😁


James
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The Quark introduced me to this wonderful side of the hobby and the sun hasn’t disappointed yet.
Solar Equipment: Solar Spectrum RG-18 0.3A, Coronado Solarmax 90mm etalon Isle of Man SN-001, Tuscon SN-380 and Meade SM2, Lunt LS80 DS, Quark Chromosphere, Lunt 2" wedge, 2-Lunt CaK II 1200, Baader 3.8 and 5.0 solar film in 208mm cells, and 3D printed Sol'Ex SHG, Lunt 40mm
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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

I wish I could report that I have been testing the filter out but as of today I have no idea of what is going on with the filter. I talked to Mark on 2/27 and he said it was ready for testing but his weather was making it difficult. I emailed him 3 weeks later, 2 weeks after that, another week later and last week but he hasn’t responded.

Has anyone heard from him lately or placed an order? I know he’s done this before and eventually he responds but from the phone call I got, I thought it was almost ready for shipping.


James
These pretzels are making me thirsty! (C.C.)
The Quark introduced me to this wonderful side of the hobby and the sun hasn’t disappointed yet.
Solar Equipment: Solar Spectrum RG-18 0.3A, Coronado Solarmax 90mm etalon Isle of Man SN-001, Tuscon SN-380 and Meade SM2, Lunt LS80 DS, Quark Chromosphere, Lunt 2" wedge, 2-Lunt CaK II 1200, Baader 3.8 and 5.0 solar film in 208mm cells, and 3D printed Sol'Ex SHG, Lunt 40mm
Coming Soon: Solar Spectrum CaK II <1A filter
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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

hopskipson wrote: Fri Apr 12, 2024 3:06 am I wish I could report that I have been testing the filter out but as of today I have no idea of what is going on with the filter. I talked to Mark on 2/27 and he said it was ready for testing but his weather was making it difficult. I emailed him 3 weeks later, 2 weeks after that, another week later and last week but he hasn’t responded.

Has anyone heard from him lately or placed an order? I know he’s done this before and eventually he responds but from the phone call I got, I thought it was almost ready for shipping.

With new products you never know.. might have not passed his final quality/performance check, but i hope for the best.


Triband C9.25

H-a: 2x Lunt40 rear mounted

WL: Antlia 500nm/ 3nm, 393 nm/ 3nm

Ca-K: homebrew (includes 2x 1.5A filters, thanks Apollo), corrective lenses (thanks again Apollo)

Cameras: imx432 + imx462
Barlows:
-2x Gerd Düring 2.7x
-2x TMB 1.8x
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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

Dennis wrote: Sun Apr 14, 2024 12:13 pm
hopskipson wrote: Fri Apr 12, 2024 3:06 am I wish I could report that I have been testing the filter out but as of today I have no idea of what is going on with the filter. I talked to Mark on 2/27 and he said it was ready for testing but his weather was making it difficult. I emailed him 3 weeks later, 2 weeks after that, another week later and last week but he hasn’t responded.

Has anyone heard from him lately or placed an order? I know he’s done this before and eventually he responds but from the phone call I got, I thought it was almost ready for shipping.

With new products you never know.. might have not passed his final quality/performance check, but i hope for the best.
Yeah I get that but a simple reply to one of my emails over a month and a half is not that much to ask. I don’t mind waiting it’s the lack of communication that makes me feel uncomfortable. Or am I being unreasonable?


James
These pretzels are making me thirsty! (C.C.)
The Quark introduced me to this wonderful side of the hobby and the sun hasn’t disappointed yet.
Solar Equipment: Solar Spectrum RG-18 0.3A, Coronado Solarmax 90mm etalon Isle of Man SN-001, Tuscon SN-380 and Meade SM2, Lunt LS80 DS, Quark Chromosphere, Lunt 2" wedge, 2-Lunt CaK II 1200, Baader 3.8 and 5.0 solar film in 208mm cells, and 3D printed Sol'Ex SHG, Lunt 40mm
Coming Soon: Solar Spectrum CaK II <1A filter
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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

hopskipson wrote: Sun Apr 14, 2024 2:33 pm
Dennis wrote: Sun Apr 14, 2024 12:13 pm
hopskipson wrote: Fri Apr 12, 2024 3:06 am I wish I could report that I have been testing the filter out but as of today I have no idea of what is going on with the filter. I talked to Mark on 2/27 and he said it was ready for testing but his weather was making it difficult. I emailed him 3 weeks later, 2 weeks after that, another week later and last week but he hasn’t responded.

Has anyone heard from him lately or placed an order? I know he’s done this before and eventually he responds but from the phone call I got, I thought it was almost ready for shipping.

With new products you never know.. might have not passed his final quality/performance check, but i hope for the best.
Yeah I get that but a simple reply to one of my emails over a month and a half is not that much to ask. I don’t mind waiting it’s the lack of communication that makes me feel uncomfortable. Or am I being unreasonable?

I dont think you are unreasonable.


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Re: New CaK etalons from Solar Spectrum

Post by Montana »

I haven't heard about mine for 18 months, even my vendor never replied to me either. I wonder if mine is lost forever :(

Alexandra


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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

Montana wrote: Mon Apr 15, 2024 9:16 am I haven't heard about mine for 18 months, even my vendor never replied to me either. I wonder if mine is lost forever :(

Alexandra
Don’t loose hope! I just got an email from Mark that the filter is ready to ship. Keep emailing them to get an update or PM Mark.

I haven’t had much time for imaging but as soon as I get this I will post an update and hopefully some images 🤞


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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

Over a week, about 4 emails and no response from Mark, if I didn’t own a Solar Spectrum filter I would be very worried. The waiting continues :roll:


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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

I heard back from Mark and the filter is on the way. It is estimated to arrive on Thursday. 🤞 I haven’t had much time for imaging but I will make time when it arrives. Don’t loose hope, Mark will get it done. Just keep trying to contact him or your dealer to get updates on the progress.


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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

hopskipson wrote: Fri May 03, 2024 10:09 pm I heard back from Mark and the filter is on the way. It is estimated to arrive on Thursday. 🤞 I haven’t had much time for imaging but I will make time when it arrives. Don’t loose hope, Mark will get it done. Just keep trying to contact him or your dealer to get updates on the progress.

Did it arrive?


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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

Dennis wrote: Sun May 12, 2024 8:34 am
hopskipson wrote: Fri May 03, 2024 10:09 pm I heard back from Mark and the filter is on the way. It is estimated to arrive on Thursday. 🤞 I haven’t had much time for imaging but I will make time when it arrives. Don’t loose hope, Mark will get it done. Just keep trying to contact him or your dealer to get updates on the progress.

Did it arrive?
Yes, it arrived on Friday. I had about 30 minutes to try it out on Saturday morning.


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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

So it arrived on Friday and I was able to try it out. I had a little trouble with my Player One Apollo Max being recognized by Firecapture so I used my ASI174 without a reducer. I'm in the middle of moving and a home renovation project so everything is a little crazy in my house. These are basically test shots. I tried to follow some of Marks's suggestions with tuning but I had very little time to capture anything and take notes. I set up in front of my house early in the morning and had to focus manually and in the sun making it difficult along with curious neighbors to take up more of the little time I had. It was very hard to see the screen and I think my focus was a little soft. I used a 102mm F/7 masked to 83mm and a 4x telecentric to give an effective focal ratio of 34.4. I only have a 200 mm Aries Derf that I fitted to the scope with some extra long bolts. It looked a little scary but thankfully it worked.
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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

And here are some pictures of the unit. When I discussed the design with Mark the blocking filter was going to be incorporated into the telecentric but he explained that he was having a legal issue with another company so he decided against it even though it was a different design. He also mentioned having an additional tilt-tuning device but decided against it to keep the bandpass as narrow as possible. Sorry the pictures are not in order.
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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

That looks very good! Congrats on the unit.

Which telecentric are you using? Powermate?
Do you remember gain and exposure levels used?


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Re: New CaK etalons from Solar Spectrum

Post by hopskipson »

Dennis wrote: Tue May 14, 2024 4:50 am That looks very good! Congrats on the unit.

Which telecentric are you using? Powermate?
Do you remember gain and exposure levels used?
I used the Baader 4x telecentric at F/34. I was also using the ASI174 so sampling was not close to critical. The exposure was 10 milliseconds and gain was about 200. I’m sure if I had the time to get the Apollo max to work or used a reducer I could have lower both. I’m not sure when I’ll get another chance to do a real test but this shows a lot of potential.


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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

hopskipson wrote: Tue May 14, 2024 12:34 pm
Dennis wrote: Tue May 14, 2024 4:50 am That looks very good! Congrats on the unit.

Which telecentric are you using? Powermate?
Do you remember gain and exposure levels used?
I used the Baader 4x telecentric at F/34. I was also using the ASI174 so sampling was not close to critical. The exposure was 10 milliseconds and gain was about 200. I’m sure if I had the time to get the Apollo max to work or used a reducer I could have lower both. I’m not sure when I’ll get another chance to do a real test but this shows a lot of potential.

Thanks, looking forward to more images.


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Re: New CaK etalons from Solar Spectrum

Post by marktownley »

Interesting and congrats on the new toy!

Very much keen to see what can be done with it with more time and a better focus!


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Re: New CaK etalons from Solar Spectrum

Post by Bob Yoesle »

The contrast looks good. Seeing and focus might be issues, but it might also be the optics are not well corrected at 394 nm. The TZ-4 definitely is not, but a new TZ-4 is rumored coming out that will be. BTW the TZ-2 will apparently be dropped - not many f15 refractors being made any more ;-)

The RG TZ-3 is corrected for CaK, and the TZ-3S and TZ-4S are also stated to also be corrected for CaK as well as Ha.

Nice to see the instructions supplied by Solar Spectrum - thanks James.

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Re: New CaK etalons from Solar Spectrum

Post by Bob Yoesle »

I received an update from Mark on my Solar Spectrum RG-18 K line filter:
Hi Bob,
I scanned the etalon I plan to use for your filter. I will be using the scan that has the numbers on the left. You will see that the FWFM said .082. This is not real. When it reads .100, these are usually in the .3-.4 range. So I really don't know how narrow they really are. It is below what the spectrometer can read. I will be putting this together this week and have the controller ready next week. So it won't be too much longer.
If this is too narrow let me know and I'll pick out another one.
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CaK Solar Spectrum etalon scan.jpg
CaK Solar Spectrum etalon scan.jpg (238.25 KiB) Viewed 1358 times

I will be saving a little money due to the fact I had a decades old ~ 2.4 A DayStar K line t-scanner whose soft-coated blockers bit the dust a long time ago. The mechanical parts remain serviceable to house the new etalon. The filter will therefore have both TEC and rapid tilt tuning ability similar to a Solar Spectrum Suna filter:

DayStar CaK T-scanner & etalon.jpg
DayStar CaK T-scanner & etalon.jpg (282.97 KiB) Viewed 1358 times

Mark also had a spun aluminum mounting for the Altair Astro 160 mm "triband" DERF that will be used for the filter with a TOA150 I purchased used a couple of years ago.

20240528_145948smcrp.jpg
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Takahashi TOA-150.jpg
Takahashi TOA-150.jpg (245.89 KiB) Viewed 1358 times

Looking forward to getting this filter after a long wait. Theoretically if double stacked with the Alluxa ~ 1.5 A CaK bandpass filter I got from Apollo it could yield near to what a ~ 0.2 A SHG image would show. Hopefully with some good weather and seeing conditions I will soon find out.

K Line stack v SHG.jpg
K Line stack v SHG.jpg (27.54 KiB) Viewed 1358 times
Note the 1% transmission levels.


But that's if all goes well on the East side of my home observatory, where after 30 years of planning and incremental work - and for the past year I've been almost totally preoccupied with - my old-school nighttime 20 inch (0.5 m) Newtonian GEM instrument is finally nearing completion:

20240515_115200sm.jpg
20240515_115200sm.jpg (154.27 KiB) Viewed 1358 times

That's me and Forrest Babcock (fellow ATM) from the Carlton Observatory Project.

Now that I've retired from EMS it's a dream that I thought I might live long enough to see get done ;-)

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Re: New CaK etalons from Solar Spectrum

Post by marktownley »

Great update Bob! You will need to tilt that Alluxa to get the most from it with the Solar Spectrum.

The kit and setups look great!


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Re: New CaK etalons from Solar Spectrum

Post by christian viladrich »

Great info Bob. Thanks for sharing !

Your future filter is looking good !


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Re: New CaK etalons from Solar Spectrum

Post by Bob Yoesle »

Thank you Mark and Christian :-)
You will need to tilt that Alluxa to get the most from it with the Solar Spectrum.
Perhaps not. Here's Mark W's measurement of my Alluxa filter:

Alluxa CaK sm.jpg
Alluxa CaK sm.jpg (259.89 KiB) Viewed 1249 times

It appears to be almost exactly on-band at room temp. with no tilt. In my conversations with Christian, he also apparently has one of these as well.

The data I received from Alluxa shows only three of the filters produced had a CWL that were close to being on band with no tilt. Two were made available from Apollo - number 3 and number 5, both of which were baked at 200 C for two hours to adjust the CWL (click for larger):

Alluxa CaK 0.1 CaK filter specs no 3 & 5 highlight.png
Alluxa CaK 0.1 CaK filter specs no 3 & 5 highlight.png (52.92 KiB) Viewed 1249 times

According to Christian, Apollo told him that he kept filter number 4. The other filters had a higher CWL and would need some degree of tilt. As with H alpha filters, tilt might also widen the bandpass and reduce the transmission to some degree.

According to both Christian and Mark, hard coated filters are relatively temperature stable:

CaK Alluxa temp drift.jpg
CaK Alluxa temp drift.jpg (8.81 KiB) Viewed 1249 times

Given the width of the CaK line, Mark advised no tilt be used with the Alluxa filter in conjunction with the new SS K line. But I will probably put it in a filter tilter from Oliver (BelOptik) just to have the ability to see how it may respond, especially as my ambient temps in the summer can get quite warm (38 C +). I have a makeshift CaK filter module with multiple tilters for playing around with.

CaK imaging module SM.jpg
CaK imaging module SM.jpg (483.27 KiB) Viewed 1249 times

The Research Grade TZ-3 is ideally corrected for CaK, and has a focal reducer designed specifically for it. As soon as Baader comes out with their new TZ-4 that is also CaK corrected, I'll likely get that so I can achieve ~ f30 with the TOA150 (f7.3) at full aperture if the opportunity presents itself.

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Re: New CaK etalons from Solar Spectrum

Post by marktownley »

Hiya Bob

Only my experience here with my CaK double stack, and this is two filters not an etalon, so maybe an apples 'vs' oranges comparison. I found running my Alluxa at f15 means I can use it will minimal tilt, however wehn I double stacked it I found that if the double stacking filter (one closest the camera) if it was not tilted (only a couple of degrees max) then there was a reflection / ghost image visible superimposed over the main image. I think Christian had a similar problem with a reflection / ghost with his double stacked Alluxa (don't know if he solved it?).

Over the years I seem to have managed to collect several filters from CaK PSTs and all of these (as you've seen with yours!) are very uniform in terms of being on band etc. With any of the CAK PST filters if I used these to double stack with the Alluxa then I would get ghosting issues. The solution I found was the Chroma filter, mine, as yours I believe, is not natively on band and required tilt. This tilt was exactly what was needed to double stack with the Alluxa, and i've been pleased with the results.

So, guess what i'm saying is when you double stack the Solar Spectrum with the Alluxa, if you have ghosting try your Chroma instead.

Mark


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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

If the filter is exactly on band in the Alluxa measurements this means with a light beam angle of incidence of 0°. Now if you use the filter with a telecentric there will be not that exact AOI, or? So a bit of blue shift might come with the real imaging train. Then you need temperature to get it on band. Just a thought.


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Re: New CaK etalons from Solar Spectrum

Post by christian viladrich »

marktownley wrote: Sun Jun 02, 2024 6:49 am Hiya Bob

Only my experience here with my CaK double stack, and this is two filters not an etalon, so maybe an apples 'vs' oranges comparison. I found running my Alluxa at f15 means I can use it will minimal tilt, however wehn I double stacked it I found that if the double stacking filter (one closest the camera) if it was not tilted (only a couple of degrees max) then there was a reflection / ghost image visible superimposed over the main image. I think Christian had a similar problem with a reflection / ghost with his double stacked Alluxa (don't know if he solved it?).

Over the years I seem to have managed to collect several filters from CaK PSTs and all of these (as you've seen with yours!) are very uniform in terms of being on band etc. With any of the CAK PST filters if I used these to double stack with the Alluxa then I would get ghosting issues. The solution I found was the Chroma filter, mine, as yours I believe, is not natively on band and required tilt. This tilt was exactly what was needed to double stack with the Alluxa, and i've been pleased with the results.

So, guess what i'm saying is when you double stack the Solar Spectrum with the Alluxa, if you have ghosting try your Chroma instead.

Mark
Hi there,

Indeed, I had some annoying issue with refection/ghost in the double/triple stack configuration with the TOA 150. Finally, I solved it this way:
- I now use the Airylab 2.7 x telecentric instead of the Baader FFC,
- this provided more back focus (= more back focus after the teleccentric compared to the FFC),
- accordingly, I can use spacers (25 mm long) between the different filters (the longer the spacers the better),
- in the triple-stack configuration, I've found that using a EO394-10 nm (with a large tilt) might be a better way to deal with reflection than using the 393-0.38 nm at a lower tilt. There, the EO393-10 nm (or the 393-0.38 nm) comes in first position after the telecentric. It is currently a bit exploratory. I have not yet made up my mind about it.

With the 300 mm Newtonian, the simple stack configuration (in fact EO 394-10 nm + Alluxa 0.14 nm) is simply a nightmare. Last year, I find no way to solve this issue. I'll try again this year, maybe with telecentric Barlow and/or other cameras (to increase backfocus and to be able to add some spacers).

I don't understand the reason why of this ghost issue with Alluxa filters. Is it a problem of design (AR coating ?). Is it more general and specific to filters having very narrow bandpass ? In comparison, there is no issue at all with 3 nm filters.


Christian Viladrich
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Re: New CaK etalons from Solar Spectrum

Post by Bob Yoesle »

Thanks for the feedback everyone!

Christian: I really don't have an idea about the reflection issue with the Alluxa filters, as I have not yet tried mine out. Alluxa might have used an AR coating on the opposite side of the filter coating, and per Mark Wagner this would be required in all hard coated filters to keep them flat once the hard-coat layers are deposited for the bandpass function. This likely is the S2 (side 2) coating indicated by the Alluxa plot below for the transmission target profile "theory", with bandpass (BP) and blocker (Blkr) coatings on side 1. Might have to contact Alluxa to know for sure.

Mark: I no longer have the Chroma filter, as Apollo offered to trade me it for the Alluxa. I was a Chroma Tech filter early adopter and learned that lesson the hard way. When my Chroma specimen was tilted enough to get on band it broadened and performed about the same as the 2.2 A CaK PST filters, and I already had a couple of those (which cost me far less!)

M Wagner CT CaK scans.jpg
M Wagner CT CaK scans.jpg (49.71 KiB) Viewed 1030 times
Note the peak transmission when tilted on-band was 55%, versus 75% when not tilted, reflecting the laws of conservation of energy.

Apollo stated the Alluxa filter I received was Part No. 5 with a CWL of 393.38 and a FWHM of 1.6 A. Having learned you cannot necessarily trust a filters specifications from the manufacturer, and the limits for hard coating technology - hence the reason etalons are superior for ultra narrow-band filtering - I had Mark Wagner measure the Alluxa filter (see my previous post) to see exactly what I had to deal with, since all the filters in a production batch have a bit of variability:

Alluxa 393.37 1.0 batch spreadsheet & graph.jpg
Alluxa 393.37 1.0 batch spreadsheet & graph.jpg (734.15 KiB) Viewed 1025 times


From Mark W's measurements, it looks like I might actually have gotten specifications closer to Part No. 3. And given the similar hard-coating technology, and the Alluxa filter will already sit in a non-collimated telecentric position, it will likely broaden and blue shift a bit without additional tilt. Perhaps that may be why Mark advised not to tilt the filter when used with his K-line etalon.

Dennis: I'll just have get going and see what happens, and if needed I may implement a small DIY temperature control system for the Alluxa filter to raise the CWL enough to allow the requisite small amount of tilt for reflection suppression and/or tuning if needed.

Or I could put the Alluxa filter ahead of the etalon with just the objective DERF and no KG3 or other pre-filtering - that may be enough to heat the filter sufficiently without mucking around with a heater. That may also deal with spurious reflections due to the mica etalon's polaroid's. This will probably be what I try first as it would be the least complicated approach: Altair DERF > TOA150 > RG TZ-3 > Alluxa (in Oliver Smie tilter) > SS K-line > [Baader reducer] > camera.

I've discovered there's always a "fly in the ointment" no matter what ATM endeavor I pursue - good thing I like to tinker...

Bob


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Re: New CaK etalons from Solar Spectrum

Post by Dennis »

Bob Yoesle wrote: Sun Jun 02, 2024 2:52 pm
Dennis: I'll just have get going and see what happens, and if needed I may implement a small DIY temperature control system for the Alluxa filter to raise the CWL enough to allow the requisite small amount of tilt for reflection suppression and/or tuning if needed.

Or I could put the Alluxa filter ahead of the etalon with just the objective DERF and no KG3 or other pre-filtering - that may be enough to heat the filter sufficiently without mucking around with a heater. That may also deal with spurious reflections due to the mica etalon's polaroid's. This will probably be what I try first as it would be the least complicated approach: Altair DERF > TOA150 > RG TZ-3 > Alluxa (in Oliver Smie tilter) > SS K-line > [Baader reducer] > camera.

I've discovered there's always a "fly in the ointment" no matter what ATM endeavor I pursue - good thing I like to tinker...

Bob
There is always a fly in the ointment, true, but im sure you will figure it out. The solution with warming the filter by placing it more to the front sounds good. Maybe you dont need this at all and its fine like it is.

The reflections i have solved with enough space between both Alluxa filters. The nature of these reflections remind me strongly to the ones resulting from 2 air spaced etalons, so it might be related to narrow band filters in general. They didnt appear with mica spaced etalon + air spaced etalon, so i assume taking advantage of the mica etalon's polarisers as you say is a good move.


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Re: New CaK etalons from Solar Spectrum

Post by Bob Yoesle »

I spoke to Alluxa, and they confirmed the most of the filters of this type are coated on both sides: "The side 1 coating is the primary bandpass, and side 2 is the blocker, which is essentially just a wider bandpass encompassing the main bandpass (which acts as an AR), as well as all the auxiliary blocking."

They also stated there would be a significant reflection issue with two filters in series, therefore they recommend some tilt to remove these reflections. Hopefully with me the etalon's polaroid's would remove any reflection between the etalon and the filter when double stacked with the filter leading the etalon in the optical path, and perhaps with it following. I'll just have to see when the etalon arrives and where it works best - if it works at all.

Apparently the 12 completed filters shown in the spreadsheet above all came from the same 2020 production run, and no others have been made. But there are two "wafers" that were coated "identically," from which additional filters would be cut as needed as listed in their catalog for $2,314/pc. Dimensionally it sounds like their wafers are about 150 +/- mm in diameter, and after coating are scanned from center to edge to determine where to cut out the specific filter. So it sounds like you get about 12 filters out of a wafer, and therefore their could be up to 24 filters still be available for those interested in getting one or two.

Bob
Last edited by Bob Yoesle on Wed Jun 05, 2024 12:42 pm, edited 1 time in total.


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