Help with piggy-back mounting system please.

[michaelmorris]

My current observatory set up is a Meade 8" LX200 with an Orion 80ED piggy-backed on the LX200. The Orion 80ED is mounted on the LX200 with a pair of Astroengineering AC503 asymmetric mounting rings. I chose these because they were cheap and because they allowed me to mount the LX200 high in the observatory without the roof frame hitting the Orion 80ED whenever I opened the roof.

I have a Meade ETX90EC as my grab-n-go scope.

The ETX no longer fulfils what I want from a grab 'n' go scope. A better grab 'n' go set up for me would probably be my Orion 80ED mounted on a small driven mount.

So here’s the plan – sell the ETX and buy a driven EQ5 mount. Now comes the point of this posting. To make this all work I’m going to need to change the mounting system for the Orion 80ED on my LX200. If I used the current set up I would have to take the 80ED out of the asymmetric rings and remount it in a separate set of rings attached to dovetail to fit it to the EQ5. Because of the way the 80ED fits into the asymmetric mounting rings, this would be a right pain.

The obvious answer would be to change the way I mount the 80ED on to the LX200.

Option 1 – buy a separate mounting ring and dovetail for the EQ5 and get some sort of quick release mounting rings for LX200 mounting. The piggy-back mounting would have to be adjustable so that I can easily line up the 80ED with the LX200.

Option 2 – Buy a system that is made up of a mounting ring and dovetail that can be quickly moved between the LX200 and the EQ5. Again the piggy back mounting on the LX200 would have to be easily adjustable so that I can line the two up.

In both options, the LX200 mounting would have to be either very low profile (so that the roof can be opened and closed), or the mount must be very quickly and easily taken on and off (without the need to realign the 80ED) when opening and closing the roof.

I’ve looked at the ADM and Losmandy systems, but neither seems to really fit the bill.

Has anyone got any ideas?

[Bizibilder]

How about this: get three similar bars of aluminium, say 50mm x 8mm and as long as you need - 300-450mm?. On top of one goes the ED80 in its rings. This has two fitted pins sticking out of the lower surface (say 6mm diam - one near each end).

The other bars go: one on the LX200 and one on the EQ5. These have two fitted holes to take the pins.

You put the ED80 on whichever mounting bar you want and a couple of bolts will hold the two bars together - the fitted pins taking care of alignment.

To make the fitted pins - drill ALL THREE BARS TOGETHER with the two holes and use a reamer to finish. The pins can be held with loctite (superglue). The clearence on these pins will be less than one thousandth of an inch, by putting the pins around 300-400mm apart any deviation in alignment when swapping mounts should be less than negligable

You may need an engineering firm or able amateur engineer to make the bars as a reamer will set you back around £10-£15!

This system should not add too much to the overall height of the ED80/LX200 setup (12mm at worst!).

Just my tuppenceworth - I hope it sets you thinking towards a solution.

Adding a thought......

Instead of the pins you could simply use two strips of metal, one either side of the "ED80" bar. These would be wider than the "ED80" bar is thick and so would protrude below it. Then you simply drop the assembly over the "mounting bars" and alignment is taken care of automatically. There is also an added advantage with this - you could "slide" the ED80 along the mounting bars and secure in different places with bolts into a series of holes in the mounting bars.