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Functionality of Dovetail L-bracket

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#1 va1erian

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Posted 14 January 2020 - 08:02 PM

There is a dovetail L-bracket, e.g. here, https://www.amazon.c.../dp/B001DGR54O/

It is used to fix a small scope in the Alt-Az mount, or a DSLR in a star tracker. The bracket has a slotted plate to which the telescope/camera is bolted with a threaded post. However, the threaded post has some kind of washer with a lever. The lever is circled with red in the attached picture. What is the purpose of it ?  I could think only of putting a triggering cable of DSLR through it.

 

 

 



#2 Mike Lynch

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Posted 14 January 2020 - 08:15 PM

Looks like a locking lever to me !

 

Mike


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#3 Agatha

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Posted 14 January 2020 - 08:31 PM

The lever will allow you to slide the telescope or dovetail bar simply by moving it, instead of turning the knob.  Put a dovetail on there by turning the knob but not all the way tight.  Do this with the lever positioned on the left, as in your picture.  Then move the lever to the right to lock in place.  Play with it a little and you will see how it works.  

 

But you need to screw something on there to see it work.  


Edited by Agatha, 14 January 2020 - 08:34 PM.

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#4 outofsight

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Posted 14 January 2020 - 08:32 PM

Locking lever is what I'd call it, too. I sometimes use a bracket like that for binoculars and an 80mm telescope, the lever gives you the ability to quickly loosen and reorient whatever you have attached, and the quickly retighten. So I guess I'd call it a quick release locking lever. It also might help you if your screw is bottoming out with whatever you're attaching it to. 


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#5 va1erian

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Posted 14 January 2020 - 09:21 PM

The lever will allow you to slide the telescope or dovetail bar simply by moving it, instead of turning the knob.  Put a dovetail on there by turning the knob but not all the way tight.  Do this with the lever positioned on the left, as in your picture.  Then move the lever to the right to lock in place. 

 

Mmm... the others said it was a "locking lever", and you elaborated that it could be used to slide easier the optical instrument along the slotted plate. You said that one could turn the lever by maybe 10 degrees, and this would tighten/untighten the knob allowing the sliding. Is this correct ?

 

Well, I have the device. It does not work that way. I would need to turn the knob at least by half-turn (180 degrees), in order to be able to shift the camera along the slotted plate.

 

The "locking lever" is not connected to the "knob" (post). This is why I called it a "washer with lever". When I slightly untighten the knob (post), the lever can rotate freely, independently of the knob. It makes no sense to me to use the lever to tighten the knob only by few degrees. I can easily turn the knob itself.

 

Also, the tip of the lever has a hole in it. All of this made me thinking that the "lever" could be used for something else, hence I asked the public on the forum. maybe it is used as some kind of stop to prevent the camera from moving further or falling out ?


Edited by va1erian, 14 January 2020 - 09:24 PM.


#6 Agatha

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Posted 14 January 2020 - 10:16 PM

outofsight used the term, "quick release".    That is correct.  It is the same as a quick release on a bicycle wheel, if you are familiar.  

 

I have two of the devices in question.  It works exactly as described by me and others. The tension on the lever is determined by how much the main screw (via the knob) is tightened.  If you can't make it function as designed, you can remove it, but keep in mind the added length of the knob screw after the cam lever is gone.  The purpose of the lever is to make things quicker and more convenient.      Good luck.  smile.png



#7 va1erian

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Posted 15 January 2020 - 01:15 AM

outofsight used the term, "quick release".    That is correct.  

Yes, the contrivance would work as the quick release, in my (tactile) experience.



#8 Rich V.

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Posted 18 January 2020 - 01:06 PM

Yes, the contrivance would work as the quick release, in my (tactile) experience.

Have you found a solution to your problem?  Is the lever missing a threaded insert or nut? 

 

For it to function as a "quick release" it must be threaded onto the mounting stud protruding from the knob. The lever must thread up and down the stud to act as a lock nut, not only as a "washer with a lever".

 

Rich



#9 va1erian

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Posted 22 January 2020 - 06:58 AM

Have you found a solution to your problem?  Is the lever missing a threaded insert or nut? 

 

For it to function as a "quick release" it must be threaded onto the mounting stud protruding from the knob. The lever must thread up and down the stud to act as a lock nut, not only as a "washer with a lever".

 

Apparently I was wrong in my previous message. The lever would not work as a quick release. Using your terms, the lever is just rotating freely around the stud. It is like the "washer with the lever" around the knob (stud) stem. The "washer" sits around the knob (stud) stem, not around the bolt. Thus, the "washer" cannot be immobilised regarding the L-bracket by tightening the knob (stud). Its function is bizzare. 

 

The (friendly) moderator has sent me a message saying that the image of the L-bracket was not made by me, thus he removed it from my original post. But it is still accessible from the Amazon link. As a matter of fact, my L-bracket was branded Skywatcher, this one, 

https://skywatcherau...il-for-cameras/ .

 

EDIT. I examined the L-bracket more thoroughly. Indeed, you are right. Turning the lever around the mounting stud (post) by 270 degrees moves the stud up or down by 0.5 -- 1 mm. Such a small travel was hard to notice. Thus, the lever's function indeed seems to be "quick tightening/loosening".


Edited by va1erian, 22 January 2020 - 07:43 AM.


#10 va1erian

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Posted 22 January 2020 - 07:21 AM

I cannot believe it ! Someone asked the same question in 2013, and posted the same picture of the L-bracket with the similar red circle around the lever in question !

 

http://www.iceinspac...ad.php?t=115172

 

Here is the answer:

 

Hi it is a tightening lever page 4 of the Orion Teletrack mount I have one on my mount for my time lapse rig.
I put my Canon 5D mark 2 on it tighten the knob and push the lever to secure it.

It is not clear to me, though, whether the lever's "securing" function is specific to the DSLRs (camera Canon 5D in the cited example) ? Does a camera has some kind of relief in its base where the lever's head fits snugly thus providing some additional support ?


Edited by va1erian, 22 January 2020 - 07:23 AM.



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