Peter's Bodges. An occasional series.

[Peter Drew]

Having presented 1) The Todmorden Pier, 2) The "rubber band trick" to cure Crayford focuser slip, I now offer 3) The AZ3 mod.   😀

I have often recommended the AZ3 alt-az mount, it's inexpensive, sturdy and has decent manual controls.  Its main, and significant limitation is that the weight of whatever equipment is fitted lies above the alt pivot.  This results in balance that is ok in the horizontal plane but gets well out of balance as the mount is raised towards the vertical, mitigating this requires either tightening the pivot bolt or some form of counterbalancing.  Several solutions have appeared over time in the DIY section but not everybody has the facility to engineer them, being currently in lockdown has put me into this position.

I have a 60mm solar telescope that comprises a 60mm Coronado etalon and BF10 blocking filter fitted to a Skywatcher ST80 refractor, the eyepiece is a Baader zoom so the whole rig is quite heavy.  Too heavy for the holding power of the AZ3 alt bolt grip even with the telescope fitted as far forward as possible, it kept sagging backwards.  Nothing suitable to hang on it as a counterbalance and not even a spanner to tighten the alt bolt nut.  Rummaging through the odds and ends drawer I came across a Bungee cord, thinking back to Bodge2 in the series I wondered if a similar principle might apply.  I attached one end of the cord to the front of the telescope and the other to a tripod leg forming a flexible "Hargreaves Strut".  It works perfectly!  You adjust the tension so that it just holds the sag, after that the more the telescope tries to sag the more the Bungee resists, the tension existing in the pivot eliminates any play.  The advantage of this mod is that anyone could do it and it's cheap.      😀  

[Rusted]

Thank you Peter. Sheer genius as always. 

Cough: Be I ever so humble... and I'm not being flippant... but have you see this mod?

Easy Alt/Az Mount Modification

It brings the telescope's mass down to the altitude axis rather than tottering over the top.
So variations of altitude no longer upset the mounting's balance.
No tools? You could probably whip this up in 5 minutes with a butter knife and a bit of kindling.

PS: I had never seen an AZ3 until I did a search.

PS2: Don't kill the messenger.

Regards,

Sorcerer's Apprentice. 3rd Class.

[Merlin66]

Interesting solution....better suited to photographic tripods.

The "head" of the AZ3 is much higher than the central pivot, due to the slo-mo worm and the size of the head v's the top of the tripod legs I think would mean that the wooden arm needs to be >6 inches and then the scope mounted underneath has a high risk of hitting the tripod legs......

 

[happy-kat]

Picture please Peter.

I quite like the az3 for the simplicity and it does just work, but I like the idea of the bungee and it could replace my home made counter weight bar.

[Macavity]

Ah yes, wrestling with the AZ3... That takes me back! 😛

After messing about with bars, weights etc. eventually used SPRINGS (too?)!
(Some logic re. "restoring forces" depending on [scope] azimuth?) 🤔



Envisaged as an (ST102) ultra-portable setup in happier days...

Twanging Springs in the night - "You'll have someone's eye out with that"! 🤣

Edited April 16, 2020 by Macavity