Decent guide scope rings?

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Hi all - Having some Flex issues with my Orion short tube 80 mounted on my C8 with guide scope rings. I've aligned both the main scope and guide scope with a reticle, but as soon as I slew to the other side of the sky, things are way out of whack. I've tightened it pretty damn tight (so much so I fear dinting the guide scope!)

Anyone recommend some guide scope ring that will mount on my C8? I currently have a long dovetail mounted on the C8...

[adman]

it's pretty hard to go past the losmandy ones. Very solid. have a look at them on Page 2 of the Losmandy Accessories section of the Bintel online shop. Or you can get one of these (http://www.admaccessories.com/Miscellaneous_Max_Guider.htm).....I am currently resisting the urge, but I can feel I am about to cave....

Adam

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Thanks :) I may be thick, but any idea which diameter I would need for an 80mm scope? I was thinking the 108mm. Would I also need a new dovetail rail? (I have a vixen style one at the moment)

[Tandum]

Circumference divided by pi to find the diameter.

Throw a tape around where you want the rings to go.

[Visionoz]

Tim

On ADM's site there is a page to check against for the rings sizes"
http://www.admaccessories.com/Ring_Sizing_Chart.htm

HTH
Cheers
Bill

[Barrykgerdes]

Are you sure that it is the mechanical rigidity between the two telescope bodies causing the trouble. If you have the coupling as tight as you say I would suspect that the problem is somewhere else. It could be mirror shift, focuser body or any other part of the system that is not stable.

Barry

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Pretty sure - the dovetail is literally bolted on, and the scope rings are just using plastic (nylon) set screws, so I strongly suspect that is the weak link.

[Barrykgerdes]

I read your original post again and I definitely suspect mirror shift in the C8. However try the better clamps. I can't suggest any particular brand because I make my own using a figure 8 design with one on the front and one on the rear. This makes sure that the two OTA's are well bonded together.

Barry

[jjjnettie]

Change your guide ring screws.
Adam, that ADM device, I can see flexure issues with it too.
It's attached at only one point. wobble wobble

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There is no chance its mirror shift in this case - we are talking about being WAY out.

[adman]

I dunno....looks pretty solid. Its basically 2 D saddles back to back, and the moving parts are lockable....

When you say its only attached at one point, which bit do you mean?

Adam

[Tandum]

Why do you need these screws anyway? I've haven't adjusted screws on a guide scope since getting a guide camera with a decent pixel count. Get normal rings and a decent guide camera.

[adman]

Most of the time you don't need to move the guidescope around to get a star, but it does come in handy sometimes

Adam

[Tandum]

Haven't had to move mine in at least 2-3 years?
Get that FS60 :)

[adman]

yeah I guess my guidescope is like looking through a coke bottle bottom compared to the Tak :sadeyes:. Time for it to go. I can pick up the FS60 for just over $800 landed, its a no-brainer

Adam

[mithrandir]

I have pretty much the same setup - Bintel guide scope package. I have a GSO 10:1 Crayford and Orion flip mirror on the ST80.

Any movement I get is either mirror flop or something not tightened enough behind the focuser. Not the guide scope moving relative to the C8.

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I dont see how it can be mirror flop - the telrad and C8 still remain in perfect alignment - its just the ST80 scope that is out...

Everything is as tight as can be made with the nylon screws. Come to think of it though, the focuser could also be the problem. When it stops raining, I will check it out :)

[mithrandir]

Didn't you mean to say "if it ever stops raining ..."?

[gbeal]

I'll put money on the focuser.
Gary

[TrevorW]

Whats the big deal with guide rings, I stopped using them and went over to a fixed guide scope (I figured no or very little flex)

seriously it works for me, the guidescope (camera) does not have to be pointing at the target to work, just in the same general direction

I've not had an issue picking up a guide star

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I switched to metal screws instead of the nylon - problem solved! :)