If you are like me and want to mount your GS 12" Dobbie up on an EQ mount, you are going to need some pretty Heavy Duty tube rings!
I had a local engineer make me a set which work reasonably well, but who wants reasonable???
I found that the weight of the 12" tends to pull on the rings as soon as it is tilted off centre. This is why rings need to be very strong! The rings I had made are not quite strong enough and are prone to twist.
A simple solution (but it took me a lot of time investigating alternatives) is to go to an Automotive LPG installer and purchase a set of LPG mounts to hold a 14-15" LPG bottle (a standard size).
These are perfect, as the GS 12" OTA is 14" diameter.
All that is needed (in my case anyway) is to weld on some hinges and some locking devices, then line the inside of the rings with rubber. Hey Presto!
Here is a pic of the LPG bottle rings I purchased today for $55, and they are VERY VERY VERY strong!!!!
The rings are 40mm wide & 5mm thick steel!
I will post more pics as the construction moves along.
Good luck tranforming your 12" Dobbie to an EQ
Last edited by ballaratdragons; 06-07-2006 at 12:55 PM.
BRILLIANT!!!!!! I have been racking my brains about a more solid replacement for my home made rings. My GSO 12" is mounted on a pier on top of an EQ6 (original type). The rings I made work but are not really solid enough. Thanks for the idea!!!
Good idea Ken!!...BTW what type of rubber would you use to line the rings?
Dunno yet until I go to Clark Rubber and check out the densities, and grippiness. (I just made that word up, you can tell can't you )
Quote:
Originally Posted by robinsm
BRILLIANT!!!!!! I have been racking my brains about a more solid replacement for my home made rings. My GSO 12" is mounted on a pier on top of an EQ6 (original type). The rings I made work but are not really solid enough. Thanks for the idea!!!
That's why I stuck it in here Maynard, so others can use ite idea
Here is the next phase of my new 'Heavy Duty' 12" tube rings.
Below is a pic of the parts ready for welding tomorrow.
On the left are the hinges. I searched Ballarat for the right hinges but had no luck finding 40mm wide 'Heavy' hinges, so I used the one I had at home and cut it in half!
On the right are the bolts and wing nuts for the locking system.
At bottom is the mounting brackets for the locking system. It is a car exhaust U clamp base cut in half. These will be welded under the flanges with the bolts drilled and pinned into them so the bolts can pivot up into place.
Keep watching this space for updates
Hmmm, they look smaller in the pic than they actually are!
Don't post too many tips, we don't want all those dobbers using a GEM as well.
I too use mine (only a 10" though) in a dob base as well as a GEM, brilliant.
All that's left now it to fit the locking bolts and the ED80 dovetail plate.
Oh, and paint it!
Oh yeah, forgot to mention, LPG gas bottle rings come in all sorts of sizes. Might be some to fit the 10" & 8" dobbies too. Get the rings that are 5mm thick steel though, the others are a bit thin.
Pic 1: The hinges welded on
Pic 2: Lock brackets welded on
Pic 3: Rings welded to cradle
That is real handy to know (have a 12 myself).
Now that is a fine first act but I want to see how you can turn out an EQ mount (suitable for fine astrophograpy) for under $200.
I am slowly building one using ford wheel bearings in an English Equatorial configaration but am apprehensive of a result for photos.
Do you have the eq mount?
alex
Ken, I reckon you are better off lining the inside with felt instead of rubber so you are able to rotate the ota in the rings.
Geoff and Vingo,
I thought about using felt, but it ain't for optical usage, it's for imaging, so it doesn't matter which way up the scope is. Plus (as I have already discovered) the OTA is so heavy that it slides down thru the rings even when done up tight!!! So the rubber will help grip it into place and hopefully stop the dreaded slide. (can be fixed if need be).
If it becomes a nuisance and I do want to turn it in the rings, I have some proper stick-on Tube rings felt which I can attach to the rubber.
For optical use it will be plopped into the Dob mount anyway.
Quote:
Originally Posted by xelasnave
Do you have the eq mount?
Alex, where have you been for the last 6 months? You have never seen the threads about my EQ??? in here or SCP or Cloudy Nights?
Shame Shame! Guess who doesn't read the site properly
Well I must give the impression all I do is read stuff on the net and that is more or less true... however even I find that there is stuff I dont know about...I know I know you find that hard to believe but assure you that is the truth.
Missing an eq article particularly on a 12 inch such as we are both privelledged to enjoy clearly points to the need for some helpers in the Lab. I am already working 7 nights a week.
Top marks for your project I feel encouraged to keep at my project..well almost..I think I will watch for a while longer.
alex
What a great bit of innovation,
Just a thought on the hinges though.
Hinge pins are usually riveted at each end, now you have cut through it, be careful that the pins don't work thier way out. Either replace the pins with longer ones and bend the ends or a tiny weld on the cut end should hold them in position.
Don't wanna see a 12" hit the ground.
Fortunately I forsaw the problem and how I solved it was to remove the hinge pins from both halves, countersunk the cut ends, and re-inserted the pins. Then I hammered (riveted) them into the countersink.
Alex, sit back and read as I make all my mistakes. Then you will be able to get it all right when you do yours. Good luck when you attempt it and keep us up to date with yours too
Today was spent making the Dovetail Base Plate or Saddle or whatever it's correct name is.
It is constructed in the simplest way by using 2.5" x 3mm flat and 2 lengths of 1/2" steel rod.
The rods are welded along each edge off the flat creating a tapered channel for the dovetail to sit in. Then two holes are drilled and tapped for the locking screws to lock the dovetail in place.
It is heavy, but weight doesn't bother me. I'll just add another counterweight!
Here are the pics.
Pic 1: the Dovetail Saddle runs from one ring to the other giving plenty of sliding adjustment.
Pic 2: See the negative dovetail shape created by the round bars.
Pic 3: Dovetail plate and rings in place in the Saddle.
Tube Rings for GS12" Dobbie *FINISHED!!!!!!!!!!*
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