Image of the day

Captured by
Adam Livingston

Bubble Nebula

My Account

New to Astromart?

Register an account...

Need Help?

Problems w/ reflector on goto mount

Started by katydid1952, 09/17/2010 03:29PM
Posted 09/17/2010 03:29PM Opening Post
I was very excited to get my 8" f/5.9 reflector on an Orion Atlas EQG mount but after using it a few time soon found that I was chasing the eyepiece and RA finder all over with a change of target object. While looking at Capella I am comfortably standing next to the scope looking straight thru the eyepiece. But key in Vega next and I'm all of a sudden having to sit on a chair under the scope and look straight up to see into the eyepiece. What's wrong with this picture? Can one loosen the tube rings and rotate the telescope to be able to see in the eyepiece and finder without becoming a contortionist??? Help appreciated. P.S. You have my permission to laugh at the thought of me practically standing on my head to see Vega. I'm just glad I was by myself!

“I arise in the morning torn between a desire to improve the world and a desire to enjoy the world. This makes it hard to plan the day.” E.B. White
Posted 09/17/2010 04:46PM #1
Welcome to the vagaries of an equitorial mount. My feeling is that rotating rings are the best solution. However, you still have to deal with the reverse rotation problem which causes you to do multiple gyrations going from some objects to another. Planing minimizes that problem. I was able to loosen the rings on my RV6 and rotate the tube, making sure that I returned the tube to my "mark" to insure the tube remained balanced. It is easy to let the tube slip down through the rings when rotating.

Good luck
Jud

I Yam What I Yam!
Posted 09/17/2010 06:32PM | Edited 09/17/2010 06:34PM #2
Kay Howard said:

I was very excited to get my 8" f/5.9 reflector on an Orion Atlas EQG mount but after using it a few time soon found that I was chasing the eyepiece and RA finder all over with a change of target object. While looking at Capella I am comfortably standing next to the scope looking straight thru the eyepiece. But key in Vega next and I'm all of a sudden having to sit on a chair under the scope and look straight up to see into the eyepiece. What's wrong with this picture? Can one loosen the tube rings and rotate the telescope to be able to see in the eyepiece and finder without becoming a contortionist??? Help appreciated. P.S. You have my permission to laugh at the thought of me practically standing on my head to see Vega. I'm just glad I was by myself!

Kay:

Welcome to the wonderful world of the equatorially mounted Newtonian. If we were to laugh at you, we would need to laugh at ourselves as well. smile

As others have said, "Rotating Rings" are the solution. Rotating Rings are rings that allow you to rotate the tube without serious effort. They can be fancy rings that mount the tube in bearings so that you can rotate the rings to any position with ease and without concern. These are generally expensive and add some weight but work very nicely.

I have a set of rotating rings designed for an 8 inch OTA that might work very nicely that I would sell quite cheaply. They work well, carry the tube with agility and make viewing a breeze. For me, they added a bit too much weight and frankly I did not like their looks.

They are nice but I do NOT recommend them. Rather I recommend modifying your existing rings so that they perform the same functions with a minimum of effort and expense. Modifying the existing rings so that the tube rotates easily and securely have come to be known as Wilcox Rings.

This is what I have done and it works amazingly well:

The materials needed are a third ring and a sheet of bondable Teflon, available from McMaster-Carr. I use 0.020 inch thick sheet. A 12" x 12" sheet is more than enough.

So... if you loosen the existing rings to rotate the tube, you are faced with a dilemma, on one hand, if you loosen the rings only a little, there is quite a bit of friction so the tube is difficult to rotate and you may actually cause the locks to slip on the mount and thus messing up your GOTO alignment. On the other hand, if you loosen your existing rings enought that the tube turns freely, the OTA can slip down in the rings causing other problems.

So, what is needed are two improvements, a way to keep the scope from slipping down in the rings while at the same time, allowing the tube to rotated in the rings to a new position with relative ease and security.

The solution to the first part of the problem is a third ring placed above the existing top ring, this prevents the scope from slipping down. Many just purchase another pair of mounting rings and clamp one tightly above the top ring. Mark's hose might work here.

The difficulty with using the third ring, is that there are some clearance issues with between the stationary ring on the mount and that third ring. This is because the hinges screws stick out and contact each other. The solution to this is to grind recesses into the both clamps so the heads of the screws are recessed. That way the rings can easily slide past one another.

In order to reduce the friction between those two rings, I cut 4 strips of the Teflon Sheeting and bond them using Superglue to one of the faces of the rings. The rings will now slide past one another easily.

The second modification allows the existing rings to clamp the OTA with sufficient firmness that the tube is free more unwanted movement while allowing it to rotate freely.

This is relatively easy. Take the two existing clamps, open them up and strip the felt as well as you can. Next cut 8 strips of the Teflon Sheeting that are the width of the clamps and about 3 inches long. Glue these at the 45 degree positions so that each clamp has 4 strips.

And that is it... Your tube should now move smoothly and yet be held securely and be free from unwanted slop. This works as well as the commercially made rotating rings and has the advantage that it is lighter and better looking. That is the reason I no longer use my commercially made rings.

This is just one way to do it. Newtonians are scopes that allow for the owner to be creative, you understand the problems, keeping the tube secure, preventing it from slipping down while allowing it to rotate.

Hope this helps..

Jon Isaacs

(Scope with Antares Rotating Rings and expensive Handsome model)








Attached Image:

jonisaacs's attachment for post 138451