Dreaming of a Dichroic Mirror

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michael.h.f.wilkinson
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Dreaming of a Dichroic Mirror

Post by michael.h.f.wilkinson » Mon Dec 07, 2015 9:17 am

A thought just occurred to me. It should be possible to create a dichroic mirror that reflects all wavelengths shorter than e.g. 420nm, and transmits the rest, or vice-versa, this could act as a wavelength-sensitive beam splitter. I could adapt a housing of a flip-mirror to hold it at 45 deg. Used with the Tri-band ERF, I could then image white light and Ca-K simultaneously. It might be a bit tricky to get the CaK module in the right position, and I would need a lot of in focus, but it should be possible.
Solar kit: GP-C8 with Thousand Oaks Solar filter, APM 80mm F/6, Lunt Herschel Wedge, Solar Spectrum 0.3Å H-alpha filter, Beloptic Tri-Band ERF (80mm free aperture), Thousand Oaks 90mm ERF, Coronado SolarMax II 60mm with Double Stack Unit. Lunt straight B1800 Ca-K module.

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Re: Dreaming of a Dichroic Mirror

Post by marktownley » Tue Dec 08, 2015 6:03 pm

A dichroic mirror would be good indeed, I agree :)
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Re: Dreaming of a Dichroic Mirror

Post by michael.h.f.wilkinson » Tue Dec 08, 2015 8:12 pm

Next problem is where to source one
Solar kit: GP-C8 with Thousand Oaks Solar filter, APM 80mm F/6, Lunt Herschel Wedge, Solar Spectrum 0.3Å H-alpha filter, Beloptic Tri-Band ERF (80mm free aperture), Thousand Oaks 90mm ERF, Coronado SolarMax II 60mm with Double Stack Unit. Lunt straight B1800 Ca-K module.

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Re: Dreaming of a Dichroic Mirror

Post by michael.h.f.wilkinson » Tue Dec 08, 2015 8:17 pm

Actually, google is your friend, again:

http://www.thorlabs.de/thorproduct.cfm? ... r=DMLP425R

Fits the bill

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Solar kit: GP-C8 with Thousand Oaks Solar filter, APM 80mm F/6, Lunt Herschel Wedge, Solar Spectrum 0.3Å H-alpha filter, Beloptic Tri-Band ERF (80mm free aperture), Thousand Oaks 90mm ERF, Coronado SolarMax II 60mm with Double Stack Unit. Lunt straight B1800 Ca-K module.

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Valery
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Re: Dreaming of a Dichroic Mirror

Post by Valery » Wed Dec 09, 2015 4:58 am

michael.h.f.wilkinson wrote:Next problem is where to source one

The next problem is not the one you are thinking it is. The next problem is that the image which will
be formed where the light pass through a dichroic mirror will be astigmatic. To remove this astigmatism
you will need to put one more glass of about the same thickness and at opposed (the same but a negative)
45 dregree. This one can be as additional filter as well.


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Re: Dreaming of a Dichroic Mirror

Post by michael.h.f.wilkinson » Wed Dec 09, 2015 7:20 am

Depends where you put it. If you put it in a tele-centric light path (which would be easiest in terms of spacing of components) I am not sure that the diagonal dichroic would have much influence other than a slight shift, especially when working at F/20 or beyond. A clear glass of the same glass and thickness would of course correct any residual aberration
Solar kit: GP-C8 with Thousand Oaks Solar filter, APM 80mm F/6, Lunt Herschel Wedge, Solar Spectrum 0.3Å H-alpha filter, Beloptic Tri-Band ERF (80mm free aperture), Thousand Oaks 90mm ERF, Coronado SolarMax II 60mm with Double Stack Unit. Lunt straight B1800 Ca-K module.

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Re: Dreaming of a Dichroic Mirror

Post by michael.h.f.wilkinson » Wed Dec 09, 2015 12:07 pm

Just a thought: If I first collimate the beam, send it through the splitter, and then re-focus, I guess that would solve the astigmatism problem, although it may introduce many other optical headaches (collimation being the first, potentially increased SA another)/
Solar kit: GP-C8 with Thousand Oaks Solar filter, APM 80mm F/6, Lunt Herschel Wedge, Solar Spectrum 0.3Å H-alpha filter, Beloptic Tri-Band ERF (80mm free aperture), Thousand Oaks 90mm ERF, Coronado SolarMax II 60mm with Double Stack Unit. Lunt straight B1800 Ca-K module.

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