JMI Motor Focuser adapted to fit......

[centroid]

Having bought a new Meade Series 5000 APO, to replace my Skywatcher ED80, I didn't want to 'pension off' the 140 pounds worth of JMI Motor Focuser, that I used on the ED80, and have to pay out for another unit to fit the Meade.

Initially, when looking at the advertising photos of the Meade, I thought it would be very similar, if not the same, as the ED80, and that it would be just be a matter of swapping the motor focuser over to the new scope.

Unfortunately, this proved not to be the case, so I had to see if there was a way that I could fit the JMI unit to the Meade, without drilling any holes or modifying the scope, and thus voiding the warrantee.

I decided to make an adapter plate onto which the JMI motor unit could be mounted, and also make use of existing screw points on the scope.

Underneath the Meade foucuser, there are two, knurled thumb screws, one is the tension adjustment for the Crayford focuser, and the other, for locking the draw tube in place. The locking screw, I saw as surplus to requirements, as I never had the need to use one on the ED80.

I had already established that the draw tube didn't 'creep out', when my H9C was attached, with the scope pointing at the zenith, and this without any undue pressure on the tension screw. I therefore decided to use this threaded hole, as one of my fixing points.

Where the foucuser joins the OTA, there is a rotating 'slip ring', to enable the scope to be rotated through 360 degrees. Attached to this ring, via an M8 hex socket screw, is an 'L' bracket for attaching the scope to a photo tripod. Again, as the scope will be mounted in 'guide rings', this was surplus to requirements, and so the 'L' bracket was removed, leaving an 8mm threaded hole. This would be the second fixing point for my adapter plate. On the other side of the 'slip ring', is another 'thumbscrew' for locking the 'slip ring' in any position. This would remain, and be used to lock the 'slip ring'.

So now I had two fixing points, and I set about making the adapter plate. I had a bit of suitable gauge brass plate laying around, so decided to use this, and having made the necessary measurement, cut and drilled this accordingly.

The bore of the large brass cog wheel that came as part of the JMI kit for the ED80, was found to be too small to fit over the 'shoulder' at the rear of the Meade focuser thumbwheel, so I bored this out to fit, using the lathe.

I decide to use the original chromed 8mm hex head screw, that held the 'L' bracket onto the 'slip ring', but of course, without the 'L' bracket, the screw was around 6mm too long. Not wanting to cut this to length' or use another non chromed screw, I made a 6mm spacer washer, out of some black Delrin (Acetal) rod that had.

The orignal black Nylon thumbscrew, which is part of the JMI unit, and used for disengaging the drive from the scope's focuser, still functions as originally intended.

So as not to damage/scatch the anodising on the focuser, I made a plastic gasket from an ice cream carton lid, and put this between the adapter plate, and the scope.

So, job done , the JMI ED80 Motor Focuser, is now installed and working nicely on the Meade APO, without drilling any holes etc, in the new scope.

The scope is now installed in it's 'piggy back' position on the 12" LX200R, and awaiting it's 'first light', whenever the clouds decide to move off out of the way.

The first photo, shows the components parts and the adapter plate, and the second, the Motor Focuser installed on the Meade.

Dave

[brendant]

Nicely done Dave, a piece of quality re-engineering.

Brendan

[beamish]

Very nice and neat mod !

[mik]

Well done saved a bit of dosh there.

Mick