Please excuse the epic title, this is something my mind has been working on for around 2 years on and off.
I was sitting on the thinking throne today and my mind started pondering as it always does. Finally I have designed rotating rings that allow the tube of my reflector to rotate on bearings. Lowest friction, light, easy to make and most of all cheap and I mean real cheap, as cheap as you want to make it.
Before someone goes and tries to make their own I will do an instructable as I make a set for my 6" scope for dev testing.
In short it is 2 sets of hexagonal rings (circle center) with 6-8 bearings each ring allowing the tube to rotate on them. You use your already supplied rings to prevent your scope falling out, you mount bearings into your existing bolt holes so the tube rolls against bearings on both the vertical axis and horizontal axis creating a virtually frictionless but very accurate rolling surface.
The rings have a brake with adjustable pressure.
The rings are made of plywood 3 layers sandwiched together you are free to use from 12mm to 19mm ply.
The design is totally customizable and you can improve on quality depending on what you spend on what quality of material. E.g. $35 no structural ply vs $90 marine ply.
The estimated cost is around $60. Yes $60 for rings that should perform as good as the $350 Antares ones. If you were to scavenge the wood and screws all you would need is perhaps a cheap trip to bunnings for a couple of bolts and nuts and an ebay purchase for the bearings of about $10.
Things will change that's for sure, I have other projects as well so this will take some time but I have been hoarding random materials and once the bearings etc arrive from china (1 month) I can start construction. This is a project that will see completion as rotating my scopes is a major pain to me.
I have tried all sorts of wilcox rings, loosening the rings, teflon, felts etc. None have performed like I want.
At the end of the day they could be easy for me to make, I might make a few for some members if there is interest.
I will be following your progress with great interest, Steve, as the ever-changing position of the eyepiece is the main drawback to GEM mounts. I have an 8" Newt on HEQ5 and have given up trying to rotate the tube "on the run" as 9 times out of 10 I disturb the mount axes and have to re-do the star alignment. Moving between standing on the floor, standing on a footstool or sitting on an adjustable-height stool, even on a tour of a small sector of the sky, is tedious and time-consuming.
Cool, yes it is a real pain having to redo the star alignment. Its that or a wonky neck/back.
I have ordered the bearings, I ordered more than needed and that only came to $22.
When I make one for my 6" I'll scrap materials but will estimate the cost for a larger scope.
Also thinking for larger scopes more bearings would be a good idea.
The place I get them from are 3.90 for 10x of the smaller ones and $9.90 for 10x of the larger ones.. They are dirt cheap but should do the job.
In my mind im onto revision 3 or so as the basic shape stays but im working out ways to make things cheaper and easier for example bolts all the way through instead of using T nuts.
I'll keep everyone posted.
Any feedback/ideas is welcome.
Could people please post measurements of their tubes, circumference is ideal and pictures of their factory supplied rings both the top and bottom of them. Ohh also length and width of your dovetails
I have a 6" and a 12" so specs of a 10" and 8" would be great, perhaps even a 4" and a 130mm
I always thought that Patrick Moore's solution to the problem of the moving eyepiece and finder position on a Newtonian was rather elegant - a rotating head (for the secondary, eyepiece, finder, etc) on the top of the telescope. This allows for a nice rigid connection for the OTA to the mount, and means you are only turning the top end of the tube, not the whole telescope. As long as the secondary is properly centred on the slew bearing for the head, it should retain collimation in any position.
The octagonal tube also has removable panels for faster cool-down.
See attached photo of Patrick Moore's 38 cm, taken from "The Caldwell Objects and How to Observe Them" by Martin Mobberley. (That's Martin Mobberley in the picture, not Patrick Moore!)
There may be an issue if the tube is not perfectly round as well. You may have to have a known circular cradle, in which the OTA is clamped, which then rolls on the bearings.
I think I'd like to see this applied to the top end more than the whole OTA but there would then be issues around the secondary perfectly centred.... Gawd..!
Steve, was it your rotating rings that I saw at Sirius Optics a few weeks ago? If so then I think it is a very tidy and well thought out idea.
rrussell1962
i've been thinking about this for ages... I Want to equatorially mount my 10" dob..... I like the look of parallax's rotating ring sets... Pricey though i guess.
I know i'm unfashionable, but i dont' want to go down the servocat or equatorial platofrm path.
I have just finished making my 10" dob a dual mount scope. $39.00 tube rings from Andrews and a home made adapter plate to my portable eq pier and similar for the guide/finder scope. Pic of the scope and a quick test shot. Bit of fine tuning with balance but it seems to be working well. I only have a single axis drive so my subs are limited to about 20sec. This one is about 2 min total exposure.
Very good. The best of both worlds. But do you miss the rotating rings from your older scope?
Yes I do miss them, it makes life so much easier when you can always have the eye piece in the right spot. I still have the 8" and have left the dob mounts on the 10" tube so I can easily swap between the two scopes and mounts.
i've just purchased a g-11 mount for my 10". Am planning to get the parallax rotating rings for it. Only problem is I have to rebuild my whole OTA to make it fit!! (needs doing anyway).
