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Help me with your Vixen BT81-SA

Binoculars Mount
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16 replies to this topic

#1 Ira

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Posted 29 November 2021 - 09:43 AM

Another oddity with my newVixen binos is the size of its built in dovetail bar, which Vixen describes as a standard Vixen dovetail. But it is not. I measure a standard Vixen dovetail (wide side)as 40.5mm. The dovetail bar on my binos is 44mm and doesn't fit a standard Vixen plate. How big is the one on your Vixen binos?

Edited by Ira, 29 November 2021 - 10:19 AM.


#2 astrokeith

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Posted 29 November 2021 - 09:47 AM

Vixen dovetails are usually in the range 42-44mm (widest side). Looks like your bins have the right size.



#3 Ira

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Posted 29 November 2021 - 09:54 AM

When I measure a randomly selected Vixen dovetail bar it measures exactly 40.5mm. I am using the dovetail on a Teleskop-Service bino swing mount. Every Vixen dovetail bar I have ever used fits, except for the dovetail bar on the binos. Could the TS mount be that far out of spec?

#4 Pinac

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Posted 29 November 2021 - 10:04 AM

The dovetail on both of my Vixen BTs - one BT 81, one BT 70 ED - measure exactly 44mm, in line with what  astrokeith indicated.

What the heck have you been buying from TS then???



#5 Ira

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Posted 29 November 2021 - 10:07 AM

The dovetail on both of my Vixen BTs - one BT 81, one BT 70 ED - measure exactly 44mm, in line with what astrokeith indicated.
What the heck have you been buying from TS then???


And you have a Vixen dovetail clamp that holds a 44mm vixen dovetail bar?

#6 Ira

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Posted 29 November 2021 - 10:14 AM

Ok, my bad. Yes, it's the wide side of the bar that goes in the plate. The wide side of my Vixen bars is 40.5mm. They all fit my swing bar Vixen clamp. The bar on the binos is 44mm. It does not fit the plate. Are you saying the plate is off?

Edited by Ira, 29 November 2021 - 10:18 AM.


#7 Ira

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Posted 29 November 2021 - 10:28 AM

This is the TS Vixen clamp on their swing bar mount. Every Vixen bar (40.5mm) fits it but the 44mm bar on my binos does not. I had to screw a Vixen bar to it to make it work. 

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#8 astrokeith

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Posted 29 November 2021 - 10:35 AM

44mm width is the most common, with some at 42mm. I would say your clamp is wrong. What make/style is it?



#9 astrokeith

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Posted 29 November 2021 - 10:38 AM

Here's a clip from the TS web page for that clamp......

 

Says 44mm!

 

 

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#10 Ira

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Posted 29 November 2021 - 11:15 AM

Mine must be out of spec. Will definitely not take a 44mm bar.

 

Thanks for your help as always.



#11 Pinac

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Posted 29 November 2021 - 12:03 PM

And you have a Vixen dovetail clamp that holds a 44mm vixen dovetail bar?

Yes. Takes 44 mm no problem.

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Edited by Pinac, 29 November 2021 - 12:03 PM.


#12 Ira

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Posted 29 November 2021 - 06:51 PM

Yes. Takes 44 mm no problem.

Yes, I can see how the specs are supposed to work. The only thing I can say is that the bino's dovetail bar will not go into the throat of my TS clamp. So something is off spec.


Edited by Ira, 29 November 2021 - 06:53 PM.


#13 Ira

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Posted 29 November 2021 - 07:15 PM

Pardon me if this is stupid, but if the clamp has a 44mm diameter and the bar has a 44mm diameter, the bar won't fit in the clamp. Right? There has to be some amount for clearance. So as I measure my bar and the throat of the clamp, they are both 44mm in diameter. Hence the bar won't fit in the clamp. Yes or no?

 

/Ira


Edited by Ira, 29 November 2021 - 09:24 PM.


#14 DeanD

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Posted 29 November 2021 - 10:07 PM

Isn't it 44mm at the top/throat of the clamp and wider at the bottom (~46mm)? I usually attach a base (which is 44mm wide) by angling it in slightly at the throat and then tightening it when it is seated.


Edited by DeanD, 30 November 2021 - 01:14 AM.


#15 Ira

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Posted 30 November 2021 - 08:07 AM

No, my clamp is 44mm at the bottom, narrower at the top. I can't rock the Vixen plate into it.

#16 Pinac

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Posted 30 November 2021 - 03:35 PM

In that case, I wonder whether what you bought from TS is perhaps not a legitimate Vixen BT. Can you post a photo or two from the underside of your BT?



#17 astrokeith

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Posted 01 December 2021 - 03:22 AM

In that case, I wonder whether what you bought from TS is perhaps not a legitimate Vixen BT. Can you post a photo or two from the underside of your BT?

Seems the clamp is at issue here. Many plates are specified in the range 42-44mm and so clearance should have been allowed beyond 44mm.


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