Finder scope keeps falling off - Unable to secure it- What I am doing wrong?

[brsseb]

I have a Celestron 8" Newtonian with a 9x50 finder scope on the small bracket that Celestron is using on those. And it keeps falling off. I am unable to secure it with the screw that came with. The metal screw doesnt get enough grip to hold it in place, even if I hand tight it pretty good. Its already fallen off once and hit the pavement, cripping an edge of the front lense. There must be something I have missed here. Any tips?

[knobby]

Show us a picture of how you're attaching it and we might be able to help

[John]

Perhaps the screw in the finder bracket is not long enough to press firmly on the finder foot ?

I think it's the same as the Skywatcher finder fitting - the screw on those is around 8mm long (the threaded part).

Alternatively, perhaps the thread in the finder bracket is stripped so the screw is not able to hold the finder in place ?

As knobby says, a photo would help.

[Knighty2112]

Is the finder scope like the one in the picture here's?

 

If so isn't there a rubber o-ring that goes on the inside of the holder at the opposite end of the adjustment screws that halps to keep it in place and aid setting it up correctly too? Not one hundred percent on that, but I have seen some finder scopes have such an o-ring fitted into them. 

[John]

8 minutes ago, Knighty2112 said:

Is the finder scope like the one in the picture here's?

 

If so isn't there a rubber o-ring that goes on the inside of the holder at the opposite end of the adjustment screws that halls to keep it in plac and aid setting it up correctly too? Not one hundred percent on that, but I have seen some finder scopes have such an o-ring fitted into them. 

Thats right - there should be a rubber O-ring where you say to keep the finder in it's mount.

 

[brsseb]

Yeah, its the scope on the photo. Guess the rubber is missing. Wonder where is gotten to...must have fallen off at some point, as I dont remember having this issue the first time I used it. 

Alternatively I can dremel a hole (or a crevase) for the screw to fit

[John]

You can replace the rubber ring with a thick elastic band or two. As long as it wedges the tube of the finder in place so that it's held firm at the top end of the bracket.

 

[Knighty2112]

50mm o-rings available on Astroboot here in the UK. Two on this link: one for £2.50, the other £3.00, both with postage and package on top too. Save having to drill things out or anything.  

http://www.astroboot.co.uk/AstroBoot/spare-parts-for-telescopes.html

[brsseb]

4 minutes ago, John said:

You can replace the rubber ring with a thick elastic band or two. As long as it wedges the tube of the finder in place so that it's held firm at the top end of the bracket.

 

Yeah, I will try that

But its kinda weird that the finder scope isnt fully threaded, allowing for permanent mounting. It only fits in a single position on the mount anyway. Its not like its made to slide back and forth. There is even a small notch at the back that it has to fit into (for alignment I guess). If it was on some sort of rail, like the telescope itself, I would have understood.

[Knighty2112]

9 minutes ago, John said:

You can replace the rubber ring with a thick elastic band or two. As long as it wedges the tube of the finder in place so that it's held firm at the top end of the bracket.

 

Good idea John. Nice lateral thinking there!  

[brsseb]

Hmm, I dont thing Im totally getting this..

So, I was thinking that there should be a small tip of rubber on the end of the screw that secures the finder scope to the mount. And its that whats missing here, causing the finder scope to come loose. 

But the 50mm rubber O-ring is another thing...I just noticed it actually, strapped weirdly to the top of the finder scope.  Anyone care to tell me (the N00b) what its purpose is?

Side note: The telescope came with NO documentation whatsoever. Someone at Celestron forgot to package it I guess. Ive only read the online manual for the Advanced VX mount, which was the main reason for buying this scope. I have not read anything about the scope itself and how to set it up, besides collimation which I have learned from my smaller Newtonian. And I aligned the scope and finder scope using Jupiter as the target the other day. 

[Knighty2112]

Place the o-ring on the finder scope tube, and then insert the finder scope into the finder scope holder so that the rubber o-ring goes inside the holder too, but at the front end opposite from the adjustment screws. The o-ring wedges the finder scope tube in place in the holder, and then you adjust the screws to align the finder scope with the telescope. The o-ring will stop the finder scope tube falling out of the finder scope holder. 

[Knighty2112]

User manual available on the Celestron web site.

http://www.celestron.com/browse-shop/astronomy/telescopes/advanced-vx-8-newtonian-telescope

[brsseb]

Thanks, the O-ring is in place now. 

But this isnt really the problem. Sorry if I was a bit unclear in my first post. Its that the entire finder scope, including the finder scope holder, falls off the scope. The problem is at the other end, basically. The single screw that is supposed to secure the finder scope holder to the telescope isnt getting a good grip. 

[Knighty2112]

2 minutes ago, brsseb said:

Thanks, the O-ring is in place now. 

But this isnt really the problem. Sorry if I was a bit unclear in my first post. Its that the entire finder scope, including the finder scope holder, falls off the scope. The problem is at the other end, basically. The single screw that is supposed to secure the finder scope holder to the telescope isnt getting a good grip. 

Find a small piece of rubber (10mm x 10mm x 1mm for example) that will fit into the gap where the finder scope shoe fits onto the telescope and then tighten up the screw so that the rubber is pressed against the finder scope bottom part where it sits in the shoe. This might give it extra grip to stop it slipping out of the shoe.

[brsseb]

Thanks, I will try to find some small piece of rubber to put in the shoe 

[Dave In Vermont]

You could also dremel a small dent into the base of the mounting-shoe for the screw to grip. Not a hole, just a dent. You could even file the surface-area of the base so it's rough - which would also give the screw something to grip onto.

Think outside the box 101,

Dave

[John]

1 hour ago, John said:

Perhaps the screw in the finder bracket is not long enough to press firmly on the finder foot ?

I think it's the same as the Skywatcher finder fitting - the screw on those is around 8mm long (the threaded part).

Alternatively, perhaps the thread in the finder bracket is stripped so the screw is not able to hold the finder in place ?

As knobby says, a photo would help.

I was trying ideas on the screw that holds the finder in place above.

Packing the finder foot to make it a tighter fit in the bracket would be worth trying as well but I've not found it an issue as long as the screw that holds the finder in place in it's mount is secure and has enough travel to hold the finder firmly in place.

 

 

[Dave In Vermont]

I've had the same problems with some mounting-bases coming loose and dropping the finder, so I can empathize. I've found the culprit is a hard & glossy paint-job on the base and/or the mount. Plenty of length in the screw - but they just don't like to stay tight.

Tinker away -

Dave

[brantuk]

If it's the finder shoe on the scope that's loose - you could have a stripped thread on the knurled bolt that tightens up to it - or a stripped thread inside the shoe itself. Or it could be a mismatched shoe and foot. Skywatcher and Celestron brackets are pretty much interchangeable for most finders - but occasionally I've come across one where I had to make a small mod to wedge the foot in on the night - pending getting a new shoe of the right fit.

[Tinker1947]

If its not been mentioned get a Telrad and consign the finder scope to the dustbin.....