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Re: Pst Cak filter secret - Vengeance against chroma

Posted: Wed Oct 03, 2018 9:07 pm
by Valery
C'est la vie, Apollo.

Re: Pst Cak filter secret - Vengeance against chroma

Posted: Thu Oct 04, 2018 4:15 am
by Valery
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.


Valery

Re: Pst Cak filter secret - Vengeance against chroma

Posted: Thu Oct 04, 2018 5:12 pm
by marktownley
Interesting. Shame they're not off the shelf items with the coating.

Re: Pst Cak filter secret - Vengeance against chroma

Posted: Sat Oct 06, 2018 5:06 am
by mdwmark
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.

Re: Pst Cak filter secret -

Posted: Mon Oct 08, 2018 10:33 pm
by marktownley
Very interested to see how you get on with it Apollo.

Re: Pst Cak filter secret -

Posted: Tue Oct 09, 2018 9:29 pm
by bart1805
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.

Re: Pst Cak filter secret -

Posted: Wed Oct 10, 2018 5:24 am
by marktownley
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!

Re: Pst Cak filter secret -

Posted: Wed Oct 10, 2018 5:53 am
by mdwmark
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.

Re: Pst Cak filter secret -

Posted: Tue Nov 06, 2018 5:54 am
by marktownley
Could be an interesting one ;)

Re: Pst Cak filter secret -

Posted: Wed Nov 07, 2018 2:49 pm
by Bob Yoesle
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
NF405-13_Transmission_780.gif (17.05 KiB) Viewed 1343 times

Re: Pst Cak filter secret -

Posted: Wed Nov 07, 2018 8:59 pm
by marktownley
I think used in conjunction with another filter with a similar steep profile just below 400nm could work as a basic CaK filter.