guide scope advice

[little col]

ok so the story so far is , i have my st80 mounted onto the 6" reflector with its original tube rings for guiding , but i have no discovered that i may need larger tube rings so i can move the guidescope to locate a good guid star.
the question is what size tube rings would be adequate for this as i dont want to get the next size rings up if i need to jump 2 sizes in diameter:shrug:
thanks colin

[[1ponders]]

For the ST80 you will want rings that are 125mm in diameter. How are you going to adjust your 80? Are you going to drill and tap 3 holes and thread bolts through them?

[little col]

cheers paul , yes i was going to drill the rings but it may be an issue getting them tapped for screwing the bolts in , is there another way?

[[1ponders]]

Yep, buy some guiderings. ;) Orion make guiderings exactly that size and using the threaded bolt principle, as do many other companies, Orion are probably just the cheapest. You get what you pay for though :rolleyes:. If you remove the plastic bolt they use (so as not to scratch the scope but they really aren't strong enough and flex under weight bearing) and replace with plastic tipped metal bolts the rings work a treat. Or alternately you can search for better quality ones (AMD I think are another brand). I use losmandy, but you need to buy a dovetail plate to go with that and they are not cheap, but definately worth it. If you don't have a good mounting then you will get movement and flexure in your ring/bolts, this will cause your autoguiding to go astray.

[little col]

:thumbsup: looks like a job for weekend , thanks for the info , fingers crossed :)

[[1ponders]]

Check out some of the sites like Losmandy and some of the suppliers to get some ideas.

[Terry B]

You could do it yourself. Taps are pretty cheap from your local hardware store.

[little col]

hmm , may not be going ahead with this as i think that "differential flexure" may be an issue:shrug: