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Brand new ES 12” Truss Dob mirror sliding around

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#1 ewack16

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Posted 05 August 2020 - 10:42 PM

F926B5EC-1DDD-473A-A8B0-65804235C798.jpeg I just got my new Explore Scientific Truss Dobsonian today and when I was putting it together I noticed that the primary mirror slides around a lot when I tilt the mirror box. I inspected the underside of the mirror box and it looks like the primary is attached to the box by 3 straps but they are very loose. It looks like the assemblers may have screwed them in wrong and I can’t figure out any way to make them all tight. If anyone has this scope could you share a photo of how the straps are attached?

 

Attached is a photo of how mine are currently attached. Thanks in advance! 



#2 Bokchoy Ninja

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Posted 05 August 2020 - 11:34 PM

Call Explore Scientific's customer support. They'll either guide you through it or replace it.


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#3 ewack16

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Posted 06 August 2020 - 01:10 AM

Update: I fixed the problem by twisting the straps to tighten them. I’m not sure if that is what is intended but it seems to work well


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#4 clusterbuster

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Posted 06 August 2020 - 01:12 AM

Update: I fixed the problem by twisting the straps to tighten them. I’m not sure if that is what is intended but it seems to work well

Good. Now enjoy those views.

 Big Dobs are Fun !

 Mark



#5 av_joe

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Posted 06 August 2020 - 01:27 AM

THe straps are used to secure the mirror to prevent it from falling off the supports. Pulling them too hard could cause tension on the mirror.

#6 Olle Eriksson

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Posted 06 August 2020 - 03:39 AM

Yeah I wouldn't expect the point of those straps to be to hold the mirror in place, but rather just prevent it from falling out. I would expect them to be loose so the mirror is free to move. Adding tension to the mirror should not be good. I mean the mirror should not move when you're slewing the telescope, but it should also not be held down. When you're observing the mirror will stay still. 



#7 ewack16

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Posted 06 August 2020 - 02:03 PM

I have them pretty tight right now. I’m going to loosen the straps a bit. I think it make sense to twist them a little bit since they are super loose when not twisted. Thanks for the advice!



#8 KBHornblower

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Posted 06 August 2020 - 06:17 PM

I can't tell where the other ends of those straps go.  Can you post a front view?  What holds the mirror in place in normal observing position?



#9 av_joe

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Posted 06 August 2020 - 10:01 PM

They end up glued to the sides of the mirror.
In normale observing position, going vertical, have two rubber wheels at 90° circa.
https://www.explores...940_d5_0817.jpg

#10 Oberon

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Posted 08 August 2020 - 12:47 AM

Update: I fixed the problem by twisting the straps to tighten them. I’m not sure if that is what is intended but it seems to work well

I doubt if you had a problem in the first place; the mirror is supposed to move around freely with no mechanical stress applied. The straps are only there to ensure the mirror doesn't fall out. Tightening the straps to keep things firm will apply a mechanical force to the mirror which will distort it.



#11 Starman1

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Posted 08 August 2020 - 05:12 PM

The mirror edge rests on the 2 posts on the bottom of the cell when the scope is used.

It must be free to slide on its back, and loose in the cell with no tension.

The straps are just to prevent it from flopping out of the cell if the scope accidentally points below the horizontal.


Edited by Starman1, 08 August 2020 - 05:12 PM.



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