Pst Cak filter secret -

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Pst Cak filter secret -

Post by TheSkyBurner » Wed Oct 03, 2018 8:32 pm

The Cak magic yellow filter in the pst is as follows.

GG395 glass. Rejection band 1 ; 370nm to 393.1nm. Rejection band 2: 393.5nm to 400nm.

That's it.

It is not dual cavity. It is not triple cavity, it is nothing special. It costs almost nothing to manufacture in lots of 10. Any optical company can make these for you.

Have fun Valery! You are welcome.
:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
Production cost is less than 200$ per filter in lots of 10 at 25.4mm. It is a standard off the shelf "notch filter".
:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

GG-395 Filter Glass, 165mm x 165mm x 3mm 395FG03-165S $342
Description GG-395 Filter Glass, 165mm x 165mm x 3mm
https://www.andovercorp.com/products/co ... pass-type/

Just find a coating company and you got yourself the biggest calcium filter in the world.
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Re: Pst Cak filter secret - Vengeance against chroma

Post by Valery » Wed Oct 03, 2018 9:07 pm

C'est la vie, Apollo.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

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Re: Pst Cak filter secret - Vengeance against chroma

Post by TheSkyBurner » Wed Oct 03, 2018 10:50 pm

Valery wrote:
Wed Oct 03, 2018 9:07 pm
C'est la vie, Apollo.
For once I agree with you entirely Valery. It is clear as day that Everyone is just out to take advantage of each other in this field.

I do have some choice words for one person in particular, but I will keep them to myself. Karma is a nasty beast , and they wont able to avoid it.

I am a man of my word and trust with great faith in cosmic retribution.

C'est la vie indeed!
:movie

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Re: Pst Cak filter secret - Vengeance against chroma

Post by Valery » Thu Oct 04, 2018 4:15 am

TheSkyBurner wrote:
Wed Oct 03, 2018 10:50 pm
Valery wrote:
Wed Oct 03, 2018 9:07 pm
C'est la vie, Apollo.
For once I agree with you entirely Valery. It is clear as day that Everyone is just out to take advantage of each other in this field.

I do have some choice words for one person in particular, but I will keep them to myself. Karma is a nasty beast , and they wont able to avoid it.

I am a man of my word and trust with great faith in cosmic retribution.

C'est la vie indeed!
:movie
Apollo try to remove such words and as retribution and vengeance from your colloquial. Think about others and their motives better. And you will feel happier.
It is quite probably that a serial manufacturing of such filters with such high requirements and tight tolerances + very small volumes is really so expensive. Also, this business must be profitable enough and comparable with other works they can do more easily. In each high tech business there are a lot of factors which directly and not so directly influent on a final price of production. All these factors should be taken in to account in a process of a final price formation. Otherwise a project will fail. If a given product is the very first ever never made before, not all of these factors are clear on a designing stage and can be better estimated only after several trial runs.
If PST CaK and Lunt CaK filters are really that simple as you have described, then I'd say that Chroma Tech is not that greedy. For example, a double cavity filter made of two single cavity 1A filters will have resulting 0,75 - 0,8A FWHM and a very steep sides with well supressed skirt and cost $4000. This is about the same cost as two Lunt B3400 CaK which being double stacked will give unknown FWHM (assumably 1,8A) and much lower light transmission. So, who looks cheaper and less greedy?
Compare also with a DayStar 2A CaK Quantum filter and add here four of 5A CaH Quarks.

I'd go with Chroma Tech if their double cavity filters will be that narrow and will have a correct UV and IR blocking. Of course, I do mean a serial sample, not a beta sample.


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Re: Pst Cak filter secret - Vengeance against chroma

Post by marktownley » Thu Oct 04, 2018 5:12 pm

Interesting. Shame they're not off the shelf items with the coating.
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Re: Pst Cak filter secret - Vengeance against chroma

Post by TheSkyBurner » Sat Oct 06, 2018 2:54 am

The way the sputtering machines work now, technology wise, is like an HP printer. You insert a recipe once. It remembers it forever, and you literally click print. Most of them are touch screen interfaces too!

The problem is, making this will shut down all other orders to focus on this one part until it is done. This is why the cost was doubled. They have to dedicate a machine to this process for more extended period of time (one filter at a time), causing a build up back order delay on all other project's. So this is entirely a time delay factor causing the excessive cost.

The process is established, the R&d is complete, the prototype was a success. The recipe is finalized. Nothing needs to be done except pressing the *print* button.

To circumvent this time issue, it is as simple to print a single 100mm+ sample. Then water-jet-cut smaller circles out to fill the orders. This will maintain a reliable stock with one sample that can fill multiple orders, using the same time frame it takes to make a single 25mm piece.

It really is this simple.

If omega optical can sell these things for $300 a pop, how excessive is the profit other companies like andover are making?

With the chroma filter, you cannot even use it out of the box. Nobody is going to be able to tilt the thing, nobody is going to have an energy rejection system, and nobody is going to have a blocking filter. So the cost is actually in excess of 3 to 4000 now To have a working setup. That is why the original price tag was a perfect match, for everybody.

For 2300$ the lunt system works right out of the box and is 27% larger

The other issue is, niche sales. Nobody is buying this stuff. One sale a month? Maybe two. Omega optical has not sold a single calcium filter in over a year! That is a dead market.


In 5 years I have only delivered 20 people a skybender. If i was running a business, I would be bankrupt. This is why I give them away for free. I can literally watch the people using them, that is how small the community is..
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Re: Pst Cak filter secret - Vengeance against chroma

Post by TheSkyBurner » Sat Oct 06, 2018 3:03 am

If you think this is crazy nonsense talk, watch this video..

https://www.youtube.com/watch?v=YTML-JGRfMc

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Re: Pst Cak filter secret - Vengeance against chroma

Post by TheSkyBurner » Sat Oct 06, 2018 3:23 am

i removed this post.
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Re: Pst Cak filter secret - Vengeance against chroma

Post by TheSkyBurner » Sat Oct 06, 2018 3:53 am

i removed this post
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Re: Pst Cak filter secret - Vengeance against chroma

Post by mdwmark » Sat Oct 06, 2018 5:06 am

There prices are right in line with everyone else. That $825 for a two cavity(I would think 2 cavity would do better then OD2) at 1 piece is a good deal.
Your idea about how easy it is to make a filter may be true for an AR's or edge filter or something like a 10-20nm HW bandpass. But a ultra narrow bandpass filter is different story.
Just going from 1.5nm to 1nm Hw decreases your possible yield in half. Your sample .1nm filter, you said they got 2 out of the run. That was probable out of a 200mm plate. That puts it at $2000 each. So they did the test run as a learning curve for a discount price. I would not be surprise if you where to scan the filter from edge to edge in one axis . Then the other axis(90deg difference) you will find that one axis will have at least .2nm change in center wavelength from edge to edge. This is not to bad for a .1nm bandpass. Hard coated bandpass filters in the .1nm or under is pushing the limit on how uniform you can keep the layers. You have this idea that when you do a run, the whole plate comes out the same. But that is not how it works. So I'm not really sure why your upset with this company.
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Re: Pst Cak filter secret - Vengeance against chroma

Post by TheSkyBurner » Sat Oct 06, 2018 7:18 am

mdwmark wrote:
Sat Oct 06, 2018 5:06 am
There prices are right in line with everyone else. That $825 for a two cavity(I would think 2 cavity would do better then OD2) at 1 piece is a good deal.
Your idea about how easy it is to make a filter may be true for an AR's or edge filter or something like a 10-20nm HW bandpass. But a ultra narrow bandpass filter is different story.
Just going from 1.5nm to 1nm Hw decreases your possible yield in half. Your sample .1nm filter, you said they got 2 out of the run. That was probable out of a 200mm plate. That puts it at $2000 each. So they did the test run as a learning curve for a discount price. I would not be surprise if you where to scan the filter from edge to edge in one axis . Then the other axis(90deg difference) you will find that one axis will have at least .2nm change in center wavelength from edge to edge. This is not to bad for a .1nm bandpass. Hard coated bandpass filters in the .1nm or under is pushing the limit on how uniform you can keep the layers. You have this idea that when you do a run, the whole plate comes out the same. But that is not how it works. So I'm not really sure why your upset with this company.
Mark W.
How do you justify the coronado pst price then?

Way more parts, Way more complicated, Way more coatings. WAY less money.

I agree its a fantastic filter, but the price increase is insane. $1500 sure totally understandable. 2300$ for something you cannot use without the special keys to unlock the image, no way.

They have to at least include the blocking filter or energy rejection filter, the thing is only od4..

I offered them my tilt modules for free.

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Re: Pst Cak filter secret -

Post by TheSkyBurner » Mon Oct 08, 2018 9:56 pm

Just called the order to have a 165mm x 165mm gg395 plate coated with the pst cak parameters. 1/4 lamda double sided, sealed edges, 6mm thick, 40/20 s/d.


I also convinced my associate in south korea to make a single 180mm objective figured for 393nm transmission. BAM.

mission accomplished.

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Re: Pst Cak filter secret -

Post by marktownley » Mon Oct 08, 2018 10:33 pm

Very interested to see how you get on with it Apollo.
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Re: Pst Cak filter secret -

Post by TheSkyBurner » Mon Oct 08, 2018 11:05 pm

marktownley wrote:
Mon Oct 08, 2018 10:33 pm
Very interested to see how you get on with it Apollo.
chirstmas / new years. early 2019 for the objective delivery

first week of december for the gg filter delivery

Then a whole lot of praying for global warming to hit central usa in january :)


I also requested a different company put the same coating on 46mm kg3 glass with an SiO2 protection over coat, we will see how that goes.

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Re: Pst Cak filter secret -

Post by bart1805 » Tue Oct 09, 2018 9:29 pm

Good luck Apollo! Happy to test it when the filters are ready. (-;
The Chroma filter with the new price is way to expensive for me. But I found two (!) PST CaK's. So have got something to mod this winter.

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Re: Pst Cak filter secret -

Post by TheSkyBurner » Wed Oct 10, 2018 3:36 am

bart1805 wrote:
Tue Oct 09, 2018 9:29 pm
Good luck Apollo! Happy to test it when the filters are ready. (-;
The Chroma filter with the new price is way to expensive for me. But I found two (!) PST CaK's. So have got something to mod this winter.
How ironic, I get rid of two. You pick up two :)

If you want to modify the skybender, you can remove the eyepiece holder and use standard SCT threaded components.

like this one,, https://agenaastro.com/blue-fireball-sc ... hread.html

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Re: Pst Cak filter secret -

Post by marktownley » Wed Oct 10, 2018 5:24 am

TheSkyBurner wrote:
Wed Oct 10, 2018 3:36 am

If you want to modify the skybender, you can remove the eyepiece holder and use standard SCT threaded components.

like this one,, https://agenaastro.com/blue-fireball-sc ... hread.html
Useful to know, thanks!
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Re: Pst Cak filter secret -

Post by mdwmark » Wed Oct 10, 2018 5:53 am

Hi Apollo,
Just checking , the GG395 and the KG3 are these hard coated of soft coated?
If they are soft coated, then they will need to be used in the back of the telescope. Soft coating filters with that many layers would never come out 1/4 wave on transmission.
On the KG3 , the SiO2 overcoat , is that to protect the KG glass from water vapor? You might as well have it AR coated. It will work just as well. Plus you have an AR on the outside of the window.
When you say you are having a single 180mm lens made, You are saying that you are making a doublet with the spacing to correct for K-line. You are not making an 180mm singlet for K-line. The singlet would need to have a very long focal length to get to 1/4 wave on transmission at that diameter lens.
Mark W.

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Re: Pst Cak filter secret -

Post by TheSkyBurner » Wed Oct 10, 2018 6:18 am

marktownley wrote:
Wed Oct 10, 2018 5:24 am
TheSkyBurner wrote:
Wed Oct 10, 2018 3:36 am

If you want to modify the skybender, you can remove the eyepiece holder and use standard SCT threaded components.

like this one,, https://agenaastro.com/blue-fireball-sc ... hread.html
Useful to know, thanks!
integrates right to the back of an sct, although you should place a 5mm spacer for more clearance away from the filter cell. You can use the eyepiece holder to attach to the 1.25" reversed nosepiece and get the sct male thread back.

Skybender is super versatile... Surprised it doesn't get any publicized attention :) NSO loved it! Right now am in the process of working with Spectrum telescope to merge reliable h-alpha filters with it. Also Trying to collaborate with Siebert optics to get some manufactured telecentrics and barlows integrated, Got the stuff goin on with Al Nagler.... Im actually on my way to Tuscon Arizona for a confidentiality agreement..

Now if i can actually get the people that were supposed to take deep space images for me four years ago, things would be working out much nicer. I have had a dozen people take a skybender and just disappear :(
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003.jpg
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Re: Pst Cak filter secret -

Post by TheSkyBurner » Wed Oct 10, 2018 6:33 am

mdwmark wrote:
Wed Oct 10, 2018 5:53 am
Hi Apollo,
Just checking , the GG395 and the KG3 are these hard coated of soft coated?
If they are soft coated, then they will need to be used in the back of the telescope. Soft coating filters with that many layers would never come out 1/4 wave on transmission.
On the KG3 , the SiO2 overcoat , is that to protect the KG glass from water vapor? You might as well have it AR coated. It will work just as well. Plus you have an AR on the outside of the window.
When you say you are having a single 180mm lens made, You are saying that you are making a doublet with the spacing to correct for K-line. You are not making an 180mm singlet for K-line. The singlet would need to have a very long focal length to get to 1/4 wave on transmission at that diameter lens.
Mark W.
I requested hard coating, but Im not familiar with all the aspects that are happening. We will see , and yes i suggested the SiO2 and AR coating on the kg3 with sealed edges so it does not get humidity damage over time. That was my first concern.

The 180mm is a single piece order is what I meant. A 350-450nm AR doublet that will be at least f/8.3. Again i don't know all the information, I just know its doable and happening :)

i just pay people and tell them that nothing is impossible. They reply "okay we will try"

Both orders are placed by very well known companies.

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Re: Pst Cak filter secret -

Post by TheSkyBurner » Tue Nov 06, 2018 4:05 am


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Re: Pst Cak filter secret -

Post by marktownley » Tue Nov 06, 2018 5:54 am

Could be an interesting one ;)
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Re: Pst Cak filter secret -

Post by Bob Yoesle » Wed Nov 07, 2018 2:49 pm

Hmmm - this is a notch filter (not bandpass), hence the NF prefix. What would it be useful for in a CaK solar filter?
NF405-13_Transmission_780.gif
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Re: Pst Cak filter secret -

Post by marktownley » Wed Nov 07, 2018 8:59 pm

I think used in conjunction with another filter with a similar steep profile just below 400nm could work as a basic CaK filter.
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Re: Pst Cak filter secret -

Post by TheSkyBurner » Thu Nov 08, 2018 12:41 am

Bob Yoesle wrote:
Wed Nov 07, 2018 2:49 pm
Hmmm - this is a notch filter (not bandpass), hence the NF prefix. What would it be useful for in a CaK solar filter?

NF405-13_Transmission_780.gif
the pst cak filter is also a notch filter, i have made this conclusion that It has "rejection bandpass" applied to the 395 substrate. I only posted this thorlabs notch filter as an example to show you guys that yes, indeed this stuff is readily available off the shelf. Its just a matter of changing one simple factory spec to suit a 393 transmission more directly

Notch filter stands for "rejection bandpass". or RB.

The pst filter has "zero out of band blocking." in the sense that it does not have a metalized coating or colored substrate that is blocking all visible transmission. If the pst filter was "blocked" then it would visibly transmit blue/violet light, and the glass would not be transparent yellow when looked through it, This glass would visibly be blue or violet like UG11 when held up to a light source..

The addition of actual dielectric bandpass blocking makes the filters more expensive and harder to manufacture because of the multiple metals required to create the different refractive index layers. However, a simple rejection band coating that only reflects certain wavelengths while passing all others is fairly simple and cheap. It is consisting of just one refractive material with 24+ layers.

consider the red hot mirror coating, this is considerably a "Infrared rejection band", the filter is totally unblocked and thus tranparent to all light except infrared...

so the method to make pst cak filters, was no different mechanically than applying what its technological equivalent of an ir cut hot mirror onto a clear window. )

Simple rejection to a nicely polished gg395 (uv cold window).

Just gotta find a group of people that will throw money at you to get it done, because 10 filters is still going to cost $3,000 - $4,000 today. Even at 20mm. This is just the nature of custom optical business. 100 of them? now we are talking a significant discount on 20mm lot's.

.

Is it going to be 1 angstrom? Probably not, But then again neither is the pst cak filter.

Blockers and trimmers are still required for all narrow band solar filtration....



So as my original thread comments about the double band rejection coating, applied first coating to surface and the second coating to surface 2.

You can use this graph to visibly see how a coating on surface one that reflects 375 to 393.1 and surface 2 would reflect 393.5 to 420 would still transmit a very narrowband line from 393.2 to 393.4 . Thus reflecting all wavelengths surrounding the desired transmission.
double notch coat 393.gif
double notch coat 393.gif (704.11 KiB) Viewed 121 times

The edge steepness is obviously what is important here, but those wings are always trimmed by additional elements so accuracy is not too important.
transmission green and rejection red.jpg
transmission green and rejection red.jpg (135.45 KiB) Viewed 119 times

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