Narrowest 393.37 ever by Apollo Lasky

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Re: 393.4 bp0.1 - yes it does exist.

Post by TheSkyBurner » Fri Aug 31, 2018 3:32 am

I am throwing in the towel here, I have done everything I can with this.

i may return , but most likely i will not.

If some of you are still interested in whatever I am doing, you can try finding me at www.393nm.com
(Bob if you want a login there I will grant you permission)


Sorry again guys,


Game over.

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Re: 393.4 bp0.1 - yes it does exist.

Post by mdwmark » Fri Aug 31, 2018 4:28 am

What is all this about .1nm or .14nm at K-line. They will both give a great image. With the amount of T ,you will probably need some color glass or an ND filter to drop the transmission down or the exposure will be to fast for the camera.
I ask Bob to check if the spacers where high or low index. So I did a little design for a .1nm single cavity filter.
The design with the high index(2) came out at .09nm in the perfect world(100%). At F/30 it drop to .1nm and the T was 90%, at F/20 the Hw went to .15nm and 78%, then at F/15 it was .27nm and 52%T.
So I flip the design and made the spacer a low index(1.5). The same number of layers gave a .07nm perfect world (100%), at F/30 it drop to .1nm and 68%,at F/20 it was .24nm and 41%T,at F/15 it was .35nm and 25%T.
So either way if you keep this filter near F/30 it will be a killer filter at K-line
If your worried about IR blocking , just add some KG5. That will cut the IR after the 1200nm.
This is the same problem with fast F# you will have with any brand that is a single cavity filter.
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Re: 393.4 bp0.1 - yes it does exist.

Post by krakatoa1883 » Fri Aug 31, 2018 7:50 am

TheSkyBurner wrote:
Wed Aug 29, 2018 10:04 pm
A single energy rejection filter will also remove those wings to negligible levels. This filter can also be used with baader planetarium astrosolar film and it will still outperform anything else on the market even at .01% transmission. It will also work in a herschel wedge as is.
very interesting... does this means that it can be used with a large scope with only a front astrosolar film ?
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Re: 393.4 bp0.1 - yes it does exist.

Post by Valery » Fri Aug 31, 2018 8:11 am

Mark,

Thanks for your detailed explanations and results of your calculations. Very much appreciated.

So, as I understand (I easily may be wrong) this filter has perfect transmission, but the goal was not really only the transmission alone.
The goal was (or should be) improvements in what can be imaged with such a filter vs widely available filters like Lunt B1200/1800 CaK.

Therefore the question: if such a filter (low index spacers) can have 90% transmission and 0,8A bandwidth, then why not to make a double stack of two such filters at the same glass piece? In this DS case we can expect about 0,55A Hw and 70-80% transmission with very well supressed parasitic light from the skirt of the filter? Such a filter may start to show the details like filamets and may be even fibrils. If not, why not add one more SS filter on the separate glass. Total transmission may drop to 50% and there still be enough light to work with. But the parasitis light will be completely eliminated and spiculaes and fibrils sloud becomes visible.

Can you, please, describe some possible hidden difficulties in the realization of such a next generation imaging device for CaK?

Also, what we can expect from the same approach to a 854,21nm filter?


Thanks,


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Re: 393.4 bp0.1 - yes it does exist.

Post by Valery » Fri Aug 31, 2018 8:15 am

krakatoa1883 wrote:
Fri Aug 31, 2018 7:50 am
does this means that it can be used with a large scope with only a front astrosolar film ?
No in a real world. I tried this with Lunt CaK and can not obtain enough light to see anything on the monitor with full gain of the camera and exposure of 100ms. The same with Ha filter.
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Re: 393.4 bp0.1 - yes it does exist.

Post by MalVeauX » Fri Aug 31, 2018 1:06 pm

I for one definitely would like to see how a 0.1nm bandpass filter behaves. Having used the 1nm filter from Chroma, it's much better than just a typical near UV filter and made for very nice contrast with the PST CaK filter. I would think the 0.1nm filter would be just like a double stack. I"m super curious about two of them too. The idea of sub-angstrom CaK is very interesting, since nothing really out there allows for this on larger scopes outside of something like a research facility and/or SHG, etc.

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Re: 393.4 bp0.1 - yes it does exist.

Post by Bob Yoesle » Fri Aug 31, 2018 10:00 pm

Hi Mark,

I checked with Dick at Chroma, and he confirmed the CT393.37bp0.1 is a single cavity and high index filter design. As Mark has pointed out, a larger f ratio is better than a shorter, and Dick also mentioned use in a collimator type system.

I think Apollo deserves credit for passionately pursuing the "holy grail" of CaK filters. I think the 1 nm and KG may make for an ideal CaK ERF system. I will objectively evaluate to the best of my ability how well the 0.1 nm filter performs "real world" at f9 to f18 with an ED100. I hope to try single and DS'd with PST CaK filters, and even try and see what a triple stack might produce. Wish me luck for some good sunspots, weather and seeing...
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Re: 393.4 bp0.1 - yes it does exist.

Post by marktownley » Sat Sep 01, 2018 10:55 am

Totally agree Bob, credit and respect due to you here Apollo (I hope you are reading this!). People are most definitely interested.

I quite like the idea of incorporating into a collimator system, it was something myself and Walter were looking at, should be easy to do.

I'm guessing running the filter in a telecentric configuration will yield results somewhere in between a collimated and converging light cone setup?
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Re: 393.4 bp0.1 - yes it does exist.

Post by krakatoa1883 » Sat Sep 01, 2018 7:09 pm

MalVeauX wrote:
Fri Aug 31, 2018 1:06 pm
I for one definitely would like to see how a 0.1nm bandpass filter behaves.
me too... I would be very interested. I understood that it should be used together with the 1nm as ERF, is it correct ? could a Baader K line filter be used instead ? I already have one...
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Re: 393.4 bp0.1 - yes it does exist.

Post by Bob Yoesle » Sat Sep 01, 2018 10:17 pm

Hi Mark,

I'm assuming the same limitations r/t collimator vs. telecentrics apply to the very narrow CaK filter as they to to H alpha.

Since the filter uses a high index spacer construction, I assume this would result in better field angle performance for a collimator system compared to an air-spaced (etalon) system. Despite this, the filter is so small that any large aperture collimator system will result in high field angle magnification. This would make such a system only usable for small field hi-res use. A properly configured telecentric system might thererfore be a bit better, but here again you have the constraints of the EFL to deal with. A smaller aperture collimataor system would seem reasonable for full disc work, and per Mark W's work a telecentric system for larger aperture hi-res work with and EFR of f20-f30.

Raf, the filter is very robust according to Chroma.com. I would think the Baader CaK filter would be more than adequate. For my apples-to-apples comparison I will use a 2 inch Baader Blue CCD ERF, followed by the Badder CaK or Edmund 400 nm short pass, and possibly a KG3 for far IR. BTW, the transmission plot for the filter I just received shows a peak T of ~ 92% (!)
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Re: 393.4 bp0.1 - yes it does exist.

Post by TheSkyBurner » Sun Sep 02, 2018 4:14 am

Wow! interest in this is far greater than is visually evident, and way more than i have ever anticipated. So many people have gone to my website to find information that it got shut down today! More than 5000 individual ip addresses in one hour.

I dont think chroma would be able to produce 10% of that many orders in any reasonable amount of time.

I have to find a new host now and probably take pre paid orders if anyone else is going to jump on this.

I had no idea it was going to turn into a monster. This is just crazy now.
0C7C47AB-7BBF-4B9C-AB9B-A584B89CA203.jpeg
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Re: 393.4 bp0.1 - yes it does exist.

Post by TheSkyBurner » Sun Sep 02, 2018 4:19 am

krakatoa1883 wrote:
Fri Aug 31, 2018 7:50 am
TheSkyBurner wrote:
Wed Aug 29, 2018 10:04 pm
A single energy rejection filter will also remove those wings to negligible levels. This filter can also be used with baader planetarium astrosolar film and it will still outperform anything else on the market even at .01% transmission. It will also work in a herschel wedge as is.
very interesting... does this means that it can be used with a large scope with only a front astrosolar film ?
Transmission is so high enough on this filter that YES, regardless of what Valery tried and says, it is going to work no problem with astrosolar film, solar newtonians, and also herschel wedges. You are limited by the sensitivity of your ccd camera at this point.

People use the baader planetarium kline filter all the time and it requires astro solar film. That transmission is only 75%.

This filter is a game changer for most instances.

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Re: 393.4 bp0.1 - yes it does exist.

Post by krakatoa1883 » Sun Sep 02, 2018 8:06 am

@Bob - Thanks for you reply, I think I will add also a KG3 to the K line for IR.

@Apollo - thanks for confirmation, I am already using a Quark CaH with my solar newtonian and works fine with my Chameleon. I also noted that it passes enough light to allow imaging of the full disc with a 80mm refractor through a front ND3.8 Astrosolar foil, so I am planning to use your filter with my Mewlon 210 and the same full aperture Astrosolar grade. I'll contact you soon, thanks.
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Re: 393.4 bp0.1 - yes it does exist.

Post by Bob Yoesle » Mon Sep 03, 2018 1:43 am

My first results with the CT393.37pb0.1 are disappointing.

However, a caveat is that I did not tilt any of the filters, and spurious reflections are apparent in my old system, and even more so with the Chroma Tech filter. I will therefore have to reserve a final judgement until I can do some additional experimentation and tinkering with tilting in order to mitigate the reflection issues. All images were identical in the use of an ED 100/900 (e.g. @ f9), Baader Blue CCD, KG3, and Baader K line filter as ERF and blocking filters. Seeing was below average, exposures and processing were identical except for the actual exposure length itself, which was varied to obtain similar histogram levels:

PST single stack:
PST.jpg
PST.jpg (301.84 KiB) Viewed 302 times
Chroma single stack:
CT .jpg
CT .jpg (253.97 KiB) Viewed 302 times
PST/PST double stack:
PST PST.jpg
PST PST.jpg (281.87 KiB) Viewed 302 times
PST/Chroma double stack:
PST CT.jpg
PST CT.jpg (260.97 KiB) Viewed 302 times
Note there obvious brightness gradient, indicating a secondary out-of-focus reflection issue:
PST CT reflection.jpg
PST CT reflection.jpg (69.66 KiB) Viewed 302 times
PST/PST/Croma triple stack:
PST PST CT.jpg
PST PST CT.jpg (257.71 KiB) Viewed 302 times
Some additional machining work needs to be done in the next week or so before a better result might be obtained... and I may opt for the 400 nm sortpass cut-off instead of the Badder K line (gets rid of an extra element), and put the CT filter in a Skybender to see what effect it may have. Otherwise the fact that this is a single cavity filter may indicate it does indeed require an f20 or longer EFR for best results, while the PST filter does better at the lower focal ratio of f9 -- perhaps using a multiple cavity design with much steeper slopes of the transmission profile.

As I've discovered years ago, noting is ever as easy as we would like with narrow band filter systems...
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Re: 393.4 bp0.1 - yes it does exist.

Post by TheSkyBurner » Mon Sep 03, 2018 2:40 am

This is different from my results. I will wait to post my data until you are finished, Im using a standard meade 90mm x 800mm.

90% transmission has a difficulty issue associated with it, as exposed by my “will it burn” tests. Could be a reverse reflection from the b-ccd filter!

I will just say there is a new learning curve, for now.

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Re: 393.4 bp0.1 - yes it does exist.

Post by Bob Yoesle » Mon Sep 03, 2018 3:45 am

That is my suspicion as well. The Badder K line has one flat component and one tilted. I'm working on tilt wedges of 2 and 4 degrees, and better spacing...
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Re: 393.4 bp0.1 - yes it does exist.

Post by marktownley » Mon Sep 03, 2018 5:35 am

Can you describe the order of the filters Bob please. Where was the Chroma when those secondary reflections were occurring? I think you could safely do away with the Baader K in your stack safely with the chroma replacing it, it offers greater blocking range.
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Re: 393.4 bp0.1 - yes it does exist.

Post by Valery » Mon Sep 03, 2018 11:08 am

TheSkyBurner wrote:
Sun Sep 02, 2018 4:19 am
krakatoa1883 wrote:
Fri Aug 31, 2018 7:50 am
TheSkyBurner wrote:
Wed Aug 29, 2018 10:04 pm
A single energy rejection filter will also remove those wings to negligible levels. This filter can also be used with baader planetarium astrosolar film and it will still outperform anything else on the market even at .01% transmission. It will also work in a herschel wedge as is.
very interesting... does this means that it can be used with a large scope with only a front astrosolar film ?
Transmission is so high enough on this filter that YES, regardless of what Valery tried and says, it is going to work no problem with astrosolar film, solar newtonians, and also herschel wedges. You are limited by the sensitivity of your ccd camera at this point.

People use the baader planetarium kline filter all the time and it requires astro solar film. That transmission is only 75%.

This filter is a game changer for most instances.

Even an elementary school pupil can easily understand why the Baader K-line 75% transmission filter is OK with the AstroSolar and why your CHROMA with 92%(!) will fail. It is obvious now - you, unlike that pupil, do not understand why. This your inability to understand such elementary things perfectly confirms an earlier Frederic's Jaber judgement - you are not credible enough to discuss these elementary questions. You should remenber that your first apperance here with attempt to sell here a 1nm Chroma filter.


To krakatoa1883

Raf,

Do not waste your time with a free lunch from Apollo Lasky (SkyBurner). Astrosolar will not work the way he promised. With refractors up to 6-7 it will work with Herschel prism. But only at a small scale (to keep light density higher) and never will work OK with large scale where we need extremely short exposures to freeze the seeing at such a short wave length. When image in CaK at large scale exposures longer than 6nm do not allow high res. So, such light eaters like AstroSolar and Herschel prism are not suitable for high resolution solar imaging in ultranarrow band filters.
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Re: 393.4 bp0.1 - yes it does exist.

Post by Carbon60 » Mon Sep 03, 2018 11:52 am

Bob,

Instead of using identical processing, if you were to work the heck out of the Chroma Single stack image data, what do you think would be the best possible image obtainable? From what you've posted it looks soft compared with the others. Adjusting Imppg and optimising contrast etc are you able to obtain anything approaching a good result?

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Re: 393.4 bp0.1 - yes it does exist.

Post by Valery » Mon Sep 03, 2018 4:27 pm

Carbon60 wrote:
Mon Sep 03, 2018 11:52 am
Bob,

Instead of using identical processing, if you were to work the heck out of the Chroma Single stack image data, what do you think would be the best possible image obtainable? From what you've posted it looks soft compared with the others. Adjusting Imppg and optimising contrast etc are you able to obtain anything approaching a good result?

Stu.
Hi Stu,

I believe Bob doing the comparision correctly. Harder processing can be applied to both - better and worser filters and better filter always will deliver better results.

After many years (now) experiments, I came to the obvious conclution - the better the initial filter, the better and easier achievable results will you get.

What is really important is a finesse and a transmission profile of a filter. Not only it's transmission peak % and a FWHM.

The results Bob obtained are exactly what were predicted. Single cavity filter will always loss vs similar FWHM filter with much steeper sides and heavily supressed skirt - as in a DS combination.

For CaK imaging I'd better stick with two PST or two Lunt filters as DS, as well as in a SS. There are no easy and cheap solution which will best old, well known and well developed solutions. And the best filter in performance/price ratio is two PST filters stacked as DS paired with the Baader K-line or Edmund 390nm bandpass filter. No one showed results which outperforms this combo. The only filter wich is close in performance is Barr filter owned by Christian Viladrich.

CHROMA filter needs a lot of work to improve it and to reach even the results peoples achieved with a simple Omega CaK filter, not say about what can be achieved with Coronado and Lunt filters.


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Re: 393.4 bp0.1 - yes it does exist.

Post by Bob Yoesle » Mon Sep 03, 2018 4:30 pm

Hi Mark, the CT filter was just behind the Baader K line - probably not ideal ;-) But I don't think it would have performed much differently without the reflection. Outside the reflected area still suffers compared to the PST double stack.

Hi Stu, I will be attempting a lot more with the filter prior to making the decision on whether to keep it or not. I think part of the issue of softness might be the extremely short exposure due to the high transmission, and therefore might try to knock this up a bit with some ND filters.

But my first task will be to finish my revised CaK module, which will allow for both multiple filter arrangements and tilting of all filters to hopefully mitigate reflection issues. With the highly mirrored filters such as the CT393, Baader K Line, and/or Edmund 400 Short pass, this is apparently essential and it seems pointless to continue without the implementation of small amounts of tilt.
CaK mod prelim SM.jpg
CaK mod prelim SM.jpg (349.78 KiB) Viewed 254 times
What we appear to need for CaK is a 3+ cavity filter to get the results Valery is describing:
Multi-cavity filters.jpg
Multi-cavity filters.jpg (88.06 KiB) Viewed 251 times
Since Chroma Tech has now gotten into Asronomy filters, I will see what they think it might cost to get there...
Last edited by Bob Yoesle on Tue Sep 04, 2018 9:22 am, edited 4 times in total.
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Re: 393.4 bp0.1 - yes it does exist.

Post by TheSkyBurner » Mon Sep 03, 2018 5:45 pm

Valery, keep insulting me. I will kindly you ask you to leave, or have you removed. You are an extremely rude person with no desire to help anybody out.

Rest in peace Valery, The universe has a special place for people like you.

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Re: 393.4 bp0.1 - yes it does exist.

Post by marktownley » Mon Sep 03, 2018 7:45 pm

Interesting to see how your experiments go Bob. My gut feeling is the Baader K-line is not helping the synergy. The chroma on it's own is certainly (in that configuration) not working as good as a SS CaK PST filter. The CaK PST filter is not Gaussian in it's profile I don't think either so doesn't have the wide(r) skirt in the wings as the Chroma. What was the exposure time Bob?

Valery, Apollo, please stop the flaming with each other too. This is a great thread that I don't want to be spoiled through unnecessary personal banter! Thanks guys :)
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Re: 393.4 bp0.1 - yes it does exist.

Post by christian viladrich » Mon Sep 03, 2018 7:56 pm

Interesting tests Bob !

It looks as if the filter is out of band, while it is supposed to be at 393.37 nm with no drift with temperature ?

The resolution is definitly lower compared to the Coronado CaK, but it might just be an artefact of variable seeing conditions.

Diffuse light and reflections is a big issue. On my Baader K-line, I removed the front (tilted) element since is was a major source of reflection. It is much better without it. Maybe something worth trying ?

Looking forward for your next tests with better conditions.
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Re: 393.4 bp0.1 - yes it does exist.

Post by christian viladrich » Mon Sep 03, 2018 7:56 pm

Bob, you should probably have to jump to F/20 for the next tests. F/9 is definetly to short for a 1 A filter.
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