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Hello Malcolm
Was just thinking about your issue of difficulties with bending over. I'm sure the issue of height change in alt/az is a problem for quite a few people. Two options (apart from getting some other type of scope) come to mind - an adjustable chair or a raise-able platform/mount. The fomer would be simpler and the latter would mean more of a commitment in terms of space, etc and any arrangment for a dob would need to be of considerable size.
My thinking for this relates to my own situation - I have MS and for the past 2-3 years have been using a 100mm 45 deg set of binoculars in alt/az. The binos plus mont come to around 20kg. The constant shifting around, heavy weight, changing position, etc ended up being quite tiring - mainly in terms of my legs. I did make a cats perch chair which worked well, but found it a tad irritating shifting it up and down (that's just me). As an alternative, I considered a large manfrotto tripod but was appalled at the price.
I then rigged up a wind up pier out of an old hills hoist clothesline - basically cut down the upper/lower halves, plus the internal spindle mechanism. It required a fair bit of trial and error but, imagine a shortened clothesline base on an EQ6 portable pier (all home-made) with large castors. It could then be wheeled around to appropriate spots on our deck. It wasn't elegant, but... did the job. A coat of white paint did give it a vaguely respectable appearance. (Note this has since been partly replaced with a secondhand Samson quick-set mount - easier for taking in the car!).
The clothesline mechanism I picked up for about $10 at a local recycling place - nobody seems to want them these days. And, they are exceptionally strong and well built. The lateral movement in the top section was overcome by drilling/tapping a hole and using a hand tightened bolt to lock the shaft (if that makes sense).
Anyway, it may not be suitable or feasible, but possibly some sort of adjustable platform could overcome the height changes inherent in a Dob's alt/az configuration? It would no doubt need to have a fairly wide base to avoid toppling. There was another post recently by Houghy (?) about building an electrically raise-able pier which looked very interesting.
Andrew
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