Sunday 2nd June: GEM adjustment and Solar.

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Sunday: Sunny but quite cloudy at times with a milky sky. Removed the counterweights and Dec wormwheel from the mounting. I had noticed a slight offset of the dark grease mark on the wormwheel rim. It was also rather noisy when slewing.

The image shows how I used a large Vernier caliper to asses the centration of the worm shaft relative to the wormwheels flanks. The arrows show where any difference can be measured but assumes the wormwheel has been cut accurately.

A quick skim of the brass, shim ring in the lathe and the worm was now slightly better centred between the caliper jaws. The Dec drive was now silent during some trial 90° slews.

It is important that some means of absolutely secure shaft locking is possible when the OTAs are down and the weights up [or removed.] Otherwise the Dec shaft can slide straight through the bearings and dump the heavy OTAs straight onto the ground or floor! [Whichever comes first.]

So I tightened the grub screws in the flange bearing collars. In the past I have set the Dec shaft horizontal and supported it on a timber prop. Whether this is safer depends on the balance when the weights are removed. Removal of the weights will make the OTAs swing instantly downwards! I would NOT rely on a shaft lock unless it were impossible to fail even under the most extreme imbalance and user-provocation.

I am happy to report that the AWR drive system continues to find its way back Home to the parking spot each time. It also showed excellent Alt-Az numbers when I slewed the OTAs to point the OTA at the N pole. A huge relief after endless failures due to an incorrect LST setting in AWR.

By 1500 it has reached 73.5F or 77F in the shade inside the dome. As the cloud had cleared I checked the sun in H-a and white light but saw nothing of interest there.

The best focus of the H-a scope is 3cm longer with the PST etalon in place. So the etalon optical group is a weak negative lens like a Barlow. I am wondering is this is typical and how it might affect the best spacing of the etalon from focus. 200mm inside focus is the norm to match the standard PST set-up.

A short, Fullerscopes pier [for a reflector?] is up for sale on eBay UK. Probably makes many modern tripods feel like spaghetti junction. Handy if you want to leave something out on the lawn without worrying about the weather. Only a fit and determined thief would get far with it under their arm. Further security easily arranged with a ground spike or a bolt through a paving slab.


Fullerscopes Telescope Stand | eBay

Click on any image for an enlargement.

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