What do you think about this CaK combo?

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Brett
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What do you think about this CaK combo?

Post by Brett »

I have come across an optical manufacturer that can provide me with the attached filters for a CaK scope.

I am waiting for the price quote, however, what are your thoughts about the specifications?
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Re: What do you think about this CaK combo?

Post by marktownley »

Way too wide a bandpass to show CaK detail.


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Re: What do you think about this CaK combo?

Post by Brett »

Mark, yes I agree, but this will be used in conjunction with Bob's new CaK filter. So the above will only be used as blocking and energy reduction...


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Re: What do you think about this CaK combo?

Post by Brett »

So the optical train will be: dichroic mirror, broadband filter, narrowband CaK, camera.


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Re: What do you think about this CaK combo?

Post by swisswalter »

Hi Brett

That may be useful as a prefilter, check out the price against a K-Line filter and please report


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Re: What do you think about this CaK combo?

Post by marktownley »

Are the filters you have sourced designed for energy rejection or 'visual' use? Even on the context of imaging I am including the tag of 'visual' use.


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Re: What do you think about this CaK combo?

Post by Brett »

Walter, I will keep this thread up to date as I get more info and prices.

Mark, the filters above are used as energy rejection. On their own they should not be used for visual. But, if my thinking is correct, when used in conjunction with the Omega CaK filter, it should be safe for visual. The Omega CaK safely reduces down to ND5. For 100% safety for visual use, I would check the transmission of everything carefully. At this stage for visual use I am not 100% sure. However, my aim is to image in CaK anyway.


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Re: What do you think about this CaK combo?

Post by marktownley »

What i'm getting at Brett is if the filters were originally designed to be used in say laser systems or the like for energy rejection, then optically (through the camera or visually, it does not matter) you may find that they are not optically flat or suffer from internal ghosting which has a detrimental effect. A Baader filter on the other hand are designed for visual use (be it at the eyepiece or with a camera) and as a result is optically flat and the reflections between the different filter elements are controlled.

This is why myself or Walter keep on about using a Baader K line. There is no benefit to using cheaper substitutes.


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Re: What do you think about this CaK combo?

Post by Brett »

Ah, okay Mark, I get what you are saying. Yes, the flatness and AR elements are important. However, the manufacturer can machine according my specs. I have told them that it will be for an astromical telescope used for imaging the Sun. So optical flatness should be in the 1/10L area.

I realize of course that the Baader K line is probably the best option at this stage, but it would be nice though if we could get an affordable alternative. Or better for the same price. This is why I asked about Bobs CaK as a blocker in another thread.


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Re: What do you think about this CaK combo?

Post by Merlin66 »

I have one of Bob's earlier 40A CaK filters and I'm waiting on his 2A version.
I intend to combine them for CaK imaging.
No additional filtering.


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Re: What do you think about this CaK combo?

Post by Brett »

Merlin, will you mind providing me with a link to his earlier 40A version filters?


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Re: What do you think about this CaK combo?

Post by marktownley »

Brett wrote:the manufacturer can machine according my specs. I have told them that it will be for an astromical telescope used for imaging the Sun. So optical flatness should be in the 1/10L area.
Just make sure they are designing the optical flatness at 393nm
Brett wrote:I realize of course that the Baader K line is probably the best option at this stage, but it would be nice though if we could get an affordable alternative. Or better for the same price. This is why I asked about Bobs CaK as a blocker in another thread.
I've bought a lot of filters from Bob and also from Baader, at the end of the day you pay your money and take your choice. The Baader filters have always performed considerably better than Bobs, just depends what results you are happy with.


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Re: What do you think about this CaK combo?

Post by Merlin66 »

Brett,
Correction - it was an 80A FWHM filter.....
#0391BP010-001
Purchased a couple of years ago from Bob. You'd need to check with him, re current availability.


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Re: What do you think about this CaK combo?

Post by Brett »

Thanks Merlin, are you referring to this one:

http://www.ebay.com/itm/Optical-Filter- ... 2331133f62


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Re: What do you think about this CaK combo?

Post by Merlin66 »

Yeah, that looks like the one I have.


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Re: What do you think about this CaK combo?

Post by marktownley »

Brett, I have one of these. You can use it, it will work, but I can categorically tell you there are far better alternatives. These filters are designed for energy rejection not imaging / visual use (like the omega CaK, and probably also the CaH filter, I would speculate based on Walters images). There's a reason why coronado and Lunt use a totally different design of filter than this. if you want it drop me an address via email and i'll post it to you i'm not going to use it.


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Re: What do you think about this CaK combo?

Post by swisswalter »

Hi Brett

Mark is the top CaK modder, belive him. If he is not convinced, don't buy, If Mark and I disagree, don't buy eighter ;)


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: What do you think about this CaK combo?

Post by Brett »

Mark thank you for your offer. I have sent you a mail with my address. Let me know if you did not get it.


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Re: What do you think about this CaK combo?

Post by marktownley »

Hi brett, Yes, have received it. I will get the filter in the post to you.


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Re: What do you think about this CaK combo?

Post by Brett »

Thanks Mark, that is excellent, thank you!


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