Telescope Reviews: Atlas overhaul...stop me before its too late!

The worms are adjusted by two things - the worm engagement and the end float. If these are too loose the mount will have excess 'play' if too tight the gears/motors will bind and stall (you get a nasty grinding sound like a blender trying to blend bolts ).

To set the worm engagement ( assuming you arent going the whole hog and fitting shims, bigger or smaller washers etc ) you have to get the worm carrier gear lined up. This is done by adjusting a pair of set screws that control how close to the worm gear the worm is. Its a pain for the RA worm more than the DEC. DOnt ask me why it just is.

Basically you loosen one screw and tighten the other until play goes away and then use either the motors or, with the motors removed run the gears by hand, to drive the mounts axis ( ie if adjueting the RA then move the RA axis) through 360'. If theres any binding you slacken it off until there isn't any and your there. Sounds easy BUT quite often you'll find its adjusted so that the play has gone BUT its just a teensy bit too tight and the motors wont run OR the motors are fine but there's excess play in the mount OR it seems fine but the motors will stall at one single point in the 360' rotation which means the worm carrier may be a little skew. Its made tougher by the fact that when you adjust the set screws you have to slacken slightly the carrier bolts. When these are tightened up sometimes theres a small slippage and you have to adjust again.

The worm float adjustment is similar. You have to adjust them enough so that play goes away but the mounts motors can shift the mount round. Here's the catch - BOTH can cause the same problem so you have to use both the worm carrier adjustemnt and the end float to get to a point where theres no play/minimal play but everything is smooth on motor power.

I do it by adjueting the womrs first just to get them loosely in, just far enough to be about lighgtly habd tight - set the worm engagement and then slowly adjust the float.

Its not hard to do but it does require a lot of patience to slowly work through it and accept that initially the first few times its going to be wrong.

Like collimation its something you can fiddle with eternally.

On my HEQ5 theres always some small play in the mount once its loaded up with my 8" scope. I compared this to a factory fresh unit and there always is a teensy amount of play - if you push the front or back of the scope ot he mount will show a tiny (less than 1 mm play) when pushed.

On the HEQ5 thats probably just a consequence of the length of the scope acting as a very efficient lever.

Anyway thats it really. I toyed with the idea of making up teflon shims and having the worms and worm gear specially machined to get them perfect BUT at the end of the day I only observe and I transport the scope and mount for each viewing session so that level of precsion would be wasted on me.

The HEQ5 though now tracks perfectly, its so quiet you wouldnt even know its there even on a silent night when slewing fast and unlike a lot of HEQ5 owners I find alignment is near perfect every single time with the first alignment star nearly always VERY close to the centre of the FOV. Whether the rebuild helped with that I dont know as prior to the rebuild it never had GoTo but I have seen lots of posts from people who say that even though all the right data has been entered the mount misses its targets on alignment by a large degree.

As much as anything though messing with the mount taught me quite a bit and on the whole it was fun but then I like messing about with stuff and seeing whats inside.

Edited by astro_baby (05/28/09 05:57 PM)