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AlbertoJ
member
Reged: 02/20/08
Posts: 26
Loc: Madrid (Spain)
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Hello, I´d like use a binoviewer with my Takahashi Fs 128.
Does Baader-Zeiss Mark V or Televue binoviewer will come to focus without a barlow, using a diagonal?
What is the X magnifier over monoviewing mode?
Thank you
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davidpitre
Carpal Tunnel
Reged: 05/10/05
Posts: 1824
Loc: Central Texas
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Alberto,
The Baader requires quite a bit less in-focus than the Televue when the Baader is used with it's prism diagonal.
The FS 102 has a removeable 2" adapter that allows it substantial in-focus, does it not ?
With no barlow or corrector, the binoviewer will provide the same magnification as mono. The Baader is designed to be used with one of its' correctors however, and some same you will get stray reflections without it.
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David
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Tamiji Homma
Pooh-Bah
Reged: 02/24/07
Posts: 1083
Loc: California, USA
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Quote:
Hello, I´d like use a binoviewer with my Takahashi Fs 128.
Does Baader-Zeiss Mark V or Televue binoviewer will come to focus without a barlow, using a diagonal?
What is the X magnifier over monoviewing mode?
Thank you
Hi Alberto,
I read that both Televue Bino Vue and Baader MarkV are its best optically with Amplifier Corrector/Glasspath Compensator.
Due to light reflection without Glasspath Compensator, Baader MarkV is best with 1.25x Glasspath Compensator for wide view use. I believe FS128 can come to focus if you remove all 2.7" extension tube and possibly use low profile 2" visual back adapter if inward focus distance is required.
I don't know this measurement can help you or not.
Tak TSA102 + <backfocus> + Baader T2 prism star diagonal + <binoviewer> + Zeiss 25.
backfocus 71mm: MarkV (with quick changer, 15mm high from prism)
backfocus 88mm: MarkV+1.25x (with quick changer 15mm high from prism)
backfocus 59mm: Bino Vue (directly screwed into T2 prism diagonal T-thread, 8mm high from prism)
The backfocus distance is distance between end of OTA and T2 prism diagonal housing when focus to a tree 1 K meters away. To reach to infinity, probably additional 1mm inward (toward objective lens) focus distance needed.
Tammy
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AlbertoJ
member
Reged: 02/20/08
Posts: 26
Loc: Madrid (Spain)
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Thank you for reply.
Mark V + 1.25x compensator + 90º diagonal could be a good choice.
It is said: 1.25x - alternatively installs before the Baader 90 degree prism diagonal to provide 1.45x.
Could I use any mirror diagonal instead baader prism diagonal with Mark V?
Alberto
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Tamiji Homma
Pooh-Bah
Reged: 02/24/07
Posts: 1083
Loc: California, USA
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Quote:
Thank you for reply.
Mark V + 1.25x compensator + 90º diagonal could be a good choice.
It is said: 1.25x - alternatively installs before the Baader 90 degree prism diagonal to provide 1.45x.
Could I use any mirror diagonal instead baader prism diagonal with Mark V?
Alberto
Hi Alberto,
Yes, you can use 2" nosepiece attached to Mark V. But you need to be aware of light path added by 2" nosepiece and 2" mirror based diagonal add about 30+mm light path. Going with T2 Prism Diagonal is the best solution, IMO.
Here is how it looks:
 
Tammy
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davidpitre
Carpal Tunnel
Reged: 05/10/05
Posts: 1824
Loc: Central Texas
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Is there a 1.25" nosepiece ?
I am thinking about using a Mark V with my Solar Ha setup which uses a blocking filter within a 1.25" diagonal.
Tammy. What are the eyepieces you have in your Mark V ?
They look like they have their own diopter adjustment.
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David
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Tamiji Homma
Pooh-Bah
Reged: 02/24/07
Posts: 1083
Loc: California, USA
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Quote:
Is there a 1.25" nosepiece ?
I am thinking about using a Mark V with my Solar Ha setup which uses a blocking filter within a 1.25" diagonal.
Tammy. What are the eyepieces you have in your Mark V ?
They look like they have their own diopter adjustment.
Hi David,
I believe 1.25" nosepiece adapter (#T2-14) can fit bottom of Quick Changer (T female thread) of MarkV.
I think that the eyepiece was originally designed for microscopy use. It is 3 element, 20mm eyerelief, 54 degree AFOV, diopter adjustment . It is super sharp on axis, very high contrast, very light (81 grams). It is my second most used binoviewer eyepiece.
Tammy
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NoiseJammer
super member
Reged: 09/16/07
Posts: 181
Loc: Gone walkabout
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I delayed posting this until we had clear skies and I could test it rigorously.
This is about a different scope and a different binoviewer but it may suggest a workable approach. The focal length of the scopes is similar.
It is possible to reach focus using a TOA150 / Denk II at unity power. The trick is to use the Takahashi TDM0200 diagonal and a TDR0200 adaptor usually intended for the FSQ106. The adaptor needs to be screwed directly onto the scope's CAA. At focus, I have 8 or 9 mm in-focus still available.
IIRC, the TOA150 has 214 mm back focus available and the Denk II uses about 115mm so that the FSQ diagonal is eating up about 214-115-9 mm = 90 mm (less than is common.)
I have seen a Tak diagonal the screwed directly onto the 72x1 thread found on the smaller focuser. This suggests that if you have similar backfocus available on the FS128, you should be able to get it to come to focus using a Denk II. The MkV has a somewhat shorter optical path so it should come to focus even easier.
Note that this is a big IF. I did a quick look on the web and it seems that the back focus of the FS 128 is about 178 mm - in which case I doubt that straight through operation is possible.
Clearest
Bruce, Toronto
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178 square inches of mostly shiny glass, one biph
... and way, way too much light polution.
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macular hole
super member
Reged: 08/12/09
Posts: 139
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Bruce,
Thanks for that info on the Tak FSQ diag. I asked this very question in the TSA 120 thread in the refractor forum and no one seemed to know the answer. The TSA 120 has a fair amount of backfocus available, so it may be not be an issue either way, but good to know the fsq diag is an option.
If the fsq diag is screwed directly onto the focuser, how does it line up when tightened down?
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NoiseJammer
super member
Reged: 09/16/07
Posts: 181
Loc: Gone walkabout
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I can answer this in a word - "randomly"
One of my friends has a FS-102 which has the 72x1 thread on its focuser. He has a similar adapter to the adapter that fits the FSQ106. Screwed directly into the focuser tube, the diagonal is oriented at about 8 o'clock which is somewhat inconvenient. This is easily cured if you have the small CAA.
I had a good look at his 72x1 diagonal. In all honesty, it looks like a piece that was made to order in a machine shop and screwed onto an AP Maxbright diagonal. Art certainly denies any knowledge of the design.
My friend's CAA is about 19 mm thick.
I must reiterate this - you need about 205 mm of available back focus for this to work. The Mk V binoviewer has a path length that is 22 mm shorter than the Denk II (personal correspondence with Tamiji Homma.)
The TSA-120 has 227 mm back focus available, so after installing the CAA it _should_ be fine with the Denk and it _will_ be fine with the Mk V.
Clearest
Bruce, Toronto
--------------------
178 square inches of mostly shiny glass, one biph
... and way, way too much light polution.
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