Solar Spectrum Filter. What is needed to make it work?

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Solar Spectrum Filter. What is needed to make it work?

Post by DeepSolar64 »

All,
I have a close friend who is considering a Solar Spectrum filter for his apochromatic refractors. I need to know a few things to help him. Does it require a barlow or powermate to increase fl to f30 for a parallel light beam into the etalon? Also is it like the DayStar Quark requiring an ERF at least above 80mm aperture?

What is needed to make this work?

James


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Re: Solar Spectrum Filter. What is needed to make it work?

Post by christian viladrich »

It would be to bad to use a SolarSpectrum filter without a telecentric system. Baader makes TZ-2, TZ-3 and TZ-4. The choice depends on the native f-ratio of the refractor.
What is the diameter of the refractor used ?


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Re: Solar Spectrum Filter. What is needed to make it work?

Post by Bob Yoesle »

Hi James,

Yes - but avoid a Barlow or Powermate and instead get a real telecentric lens system to give it at least f/30 (Baader or BelOptik), and an ERF above 80-100 mm is highly desirable. FYI, telecentric systems do not produce parallel light to an etalon (that is more applicable to a collimator system), rather they provide very narrow converging light cones to the filter to reach near the specified filter band-pass.

See Christian Viladrich's treatise here, section F is the Summary.

The Baader DERFs are superior in providing both UV and IR blocking (and optical quality) - especially if it is a high-end APO. No sense in being penny wise and dollar foolish at this level of filter and telescope expense.


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Re: Solar Spectrum Filter. What is needed to make it work?

Post by DeepSolar64 »

The largest is a Tak FS102. F8. He hopes to be able to use the filter on all four of his scopes.

The shorter fl scopes will take a more powerful telecentric?


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Re: Solar Spectrum Filter. What is needed to make it work?

Post by Bob Yoesle »

Hi James,

Be sure to read the link to Christian's site. I'd go with the Baader TZ4, which will give you f/32 with the Tak f/8. there generally would be no more "powerful" telecentric. I believe the TZ's were designed around an objective with an 800 mm FL, which is ideal for the FS102.

After the filter, you could use a telecompressor to re-establish a better EFR. I would use a Baader 110 mm DERF because the FS Tak is a fluorite, and thermal stability of the objective would be improved since fluorite has a large CTE.


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Re: Solar Spectrum Filter. What is needed to make it work?

Post by DeepSolar64 »

Bob Yoesle wrote: Fri Mar 19, 2021 9:57 pm Hi James,

Be sure to read the link to Christian's site. I'd go with the Baader TZ4, which will give you f/32 with the Tak f/8. there generally would be no more "powerful" telecentric. I believe the TZ's were designed around an objective with an 800 mm FL, which is ideal for the FS102.

After the filter, you could use a telecompressor to re-establish a better EFR. I would use a Baader 110 mm DERF because the FS Tak is a fluorite, and thermal stability of the objective would be improved since fluorite has a large CTE.
He may be inclined to use the TV85 more often. It’s f7 I think and could probably use the TZ4 telecentric.


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Re: Solar Spectrum Filter. What is needed to make it work?

Post by AJamesB »

I've been looking into solar spectrum as well, and something they told me was that the required F number depended on the filter rating. Filters rated for 0.5A needed f30, but those rated for 0.3A need f40, and that was something I wasn't aware of but that is good to know when working out what telecentrics and such to get.


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Re: Solar Spectrum Filter. What is needed to make it work?

Post by DeepSolar64 »

ammonthenephite wrote: Sat Mar 20, 2021 4:09 am I've been looking into solar spectrum as well, and something they told me was that the required F number depended on the filter rating. Filters rated for 0.5A needed f30, but those rated for 0.3A need f40, and that was something I wasn't aware of but that is good to know when working out what telecentrics and such to get.
The one we've looked at is 0.65A. It will give a good balance between proms and surface.


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Re: Solar Spectrum Filter. What is needed to make it work?

Post by Ljungmann »

Hi James!
You can see how it works with my filter on a 8" Baader Triband SCT. You have the TZ3, SS 0.3A, the 0.4x Baader Telecompressor....
I do have a 0.6A Quantum (Del Woods etalon) filter. It works the same way. Very close to your SS 0.65 filter. And you will be more than happy with that filter. Great views and a magnificent prominence filter. On a high end filter (and telescope) always use a Baader DERF.
IMG_1764.jpg
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Re: Solar Spectrum Filter. What is needed to make it work?

Post by christian viladrich »

ammonthenephite wrote: Sat Mar 20, 2021 4:09 am I've been looking into solar spectrum as well, and something they told me was that the required F number depended on the filter rating. Filters rated for 0.5A needed f30, but those rated for 0.3A need f40, and that was something I wasn't aware of but that is good to know when working out what telecentrics and such to get.
Hello,
Here is the effective FWHM depending on nominal FWHM and f-ratio :
http://astrosurf.com/viladrich/astro/in ... FWHM-N.JPG


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Re: Solar Spectrum Filter. What is needed to make it work?

Post by DeepSolar64 »

Thanks. That will give he and I an idea of what the correct setup looks like.


Lunt 8x32 SUNoculars
Orion 70mm Solar Telescope
Celestron AstroMaster Alt/Az Mount
Meade Coronado SolarMax II 60 DS
Meade Coronado SolarMax II 90 DS
Meade Coronado AZS Alt/Az Mount
Astro-Tech AT72EDII with Altair solar wedge
Celestron NexStar 102GT with Altair solar wedge
Losmandy AZ8 Alt/Az Mount
Sky-Watcher AZGTI Alt-Az GoTo mount
Cameras: ZWO ASI178MM, PGR Grasshopper, PGR Flea
Lunt, Coronado, TeleVue, Orion and Meade eyepieces

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