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Old 29-03-2019, 09:01 AM
Glencoe (Ian)
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Balanced Alt Az mount for refractor

Having bought a 120mm f5 refractor, I found it hard to view overhead objects due to the weight of the tube pulling down on the altitude axis - this being a simple 'tension nut' affair. Tightening it merely made it all-but-impossible to aim the scope. So I spent some time in my shed, and came up with this simple counterweight system for the alt-az mount. Its just a couple of pieces of L section aluminium with a 1.25kg weight bolted on. Now the tension bolt on the altitude axis can be all-but-loose, and the telescope is a delight to aim, with absolutely no sagging; no matter what elevation.
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Old 29-03-2019, 05:08 PM
gaseous (Patrick)
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Nice job. I've got a similar scope and anything heavier than a small plossl throws it all out. Might have to give this a whirl, cheers.
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Old 29-03-2019, 06:58 PM
Wavytone (Nick)
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Here's my G&G scope. The mount would take yours too, though the tripod is a bit flimsy. The belt drives are nice as they have enough drag to hold the scope with a tad of imbalance, yet slew nicely if the scope is pushed, and the 8:1 reduction makes fine adjustments easy enough.
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Old 30-03-2019, 08:00 AM
Glencoe (Ian)
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Here's another image, before I painted it. The tops of the two L sections are simply bolted near to where the front scope-clamp is attached; I didn't even need to drill extra bolt holes, as there happened to be some extra ones in the bracket already. Before bolting the lower end of the short rod to the longer one, I set the scope horizontally and made sure that the long rod was a good 5mm clear of the tripod legs; then used a marker pen to mark the place where the 'attachment' hole needed drilling.
Then I put in my heaviest eyepiece (a 2" 30mm) and tipped the scope up into a vertical position. This done, it was just a matter of sliding my 1.25kg weight along the long rod until I'd found the 'balance point'; once again, using the marker pen to ensure the correct point before drilling the hole. Then I simply cut of the remaining length of aluminium rod.
Happily, I found that with the rods at an angle where they just clear the tripod legs, the counterweight happens to be in a perfect 'balance' position, no matter what altitude the instrument is pointed. How's that for luck?
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Old 30-03-2019, 08:26 AM
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Ukastronomer (Jeremy)
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A 120mm refractor on an AZ3 ?

I find 80mm enough for that mount, good luck
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