Quantum back focus?

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mami813
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Quantum back focus?

Post by mami813 »

my telescope is 204mm F8.8 telescope.The filter is quantum 0.5A.

I would use a baader tz-4 magnification.

Where should the quantum be located in the telescope focus?

thank you.
Jong Ho


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Bob Yoesle
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Re: Quantum back focus?

Post by Bob Yoesle »

See this link, which most importantly shows that the objective's focal plane is located ~ 93 mm behind the front of the TZ4 telecentric lens assembly - which should remain fixed, and the resultant focal plane lies 220 mm past the end of the TZ4.

TZ4 config.jpg
TZ4 config.jpg (137.96 KiB) Viewed 1296 times

The Quantum or (Solar Spectrum) etalon system can be placed anywhere in that 220 mm distance which will allow you to use a diagonal/eyepiece/camera system. Note that any focusing should take place after the TZ unit and likely will employ extension tubes depending on the proper configuration of the downstream components.

Bob


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Re: Quantum back focus?

Post by mami813 »

Bob Yoesle wrote: Mon Oct 31, 2022 1:59 pm See this link, which most importantly shows that the objective's focal plane is located ~ 93 mm behind the front of the TZ4 telecentric lens assembly - which should remain fixed, and the resultant focal plane lies 220 mm past the end of the TZ4.


TZ4 config.jpg


The Quantum or (Solar Spectrum) etalon system can be placed anywhere in that 220 mm distance which will allow you to use a diagonal/eyepiece/camera system. Note that any focusing should take place after the TZ unit and likely will employ extension tubes depending on the proper configuration of the downstream components.

Bob
hi,Bob
Thanks for sharing the information.
Is it the same principle for Televue 4x powermate?


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Re: Quantum back focus?

Post by marktownley »

mami813 wrote: Wed Nov 02, 2022 1:32 am Is it the same principle for Televue 4x powermate?
Who knows what the exact metrics are for the powermate, TV does not share them.


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Re: Quantum back focus?

Post by Bob Yoesle »

As Mark notes, who knows what the TeleVue Powermates are specified for? They only describe these as being developed for their more recent widefield eyepiece designs.

I should also note that the TZ2 and TZ4 were specifically designed for use with an 800 mm FL objective. However, Christian Viladrich at (F) shows the TZ4 does very well with almost any FL longer than ~ 450 mm.

The other suggestion is that BelOptik can design a custom made telecentric for your specific application. If you're handy with optical design software, you can likely also design your own using off-the-shelf lenses such as Peter Zetner's telecentric.

Note there is a great deal of similarity between a collimator lens system and a telecentric lens system ;-)

Bob


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Re: Quantum back focus?

Post by mami813 »

Bob Yoesle wrote: Thu Nov 03, 2022 4:01 pm As Mark notes, who knows what the TeleVue Powermates are specified for? They only describe these as being developed for their more recent widefield eyepiece designs.

I should also note that the TZ2 and TZ4 were specifically designed for use with an 800 mm FL objective. However, Christian Viladrich at (F) shows the TZ4 does very well with almost any FL longer than ~ 450 mm.

The other suggestion is that BelOptik can design a custom made telecentric for your specific application. If you're handy with optical design software, you can likely also design your own using off-the-shelf lenses such as Peter Zetner's telecentric.

Note there is a great deal of similarity between a collimator lens system and a telecentric lens system ;-)

Bob
Hello Bob.
Thanks a lot for the information.


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