Lidl Skylux 379 Telescope

Equatorial Mount Improvements

Introduction

I'm afraid I don't have any pictures showing how to dismantle the Lidl telescope's equatorial mount, but I did a very good Austrian website that had excellent pictures of the dismantled mount, as well as some good articles on tuning the telescope. Unfortunately it has disappeared since I first wrote this page. It's probably a good idea to do your own Google search (try lidl montierung) before you start.

Dismantling the equatorial mount is not a trivial job. There are lots of parts to remove, clean, and refit, and you need to take care during reassembly. It's a good idea to make a note of what goes where as you dismantle, so keep a pencil and paper handy. Note that groups of thin plastic washers are used in various places to adjust the play of moving parts. You must make sure the right washers go back in the right places.

Dismantling

Start by removing the telescope tube, its dovetail mount and the slow motion flexible handles. Undo the screw from the end of the right ascension (RA) slow motion drive and pull off the gear wheel. Remove the counterweight and its shaft. Put all these parts well out of the way so they stay clean.

Slow motion drives

Loosen the RA and declination clamping screws. Slightly loosen the lock nuts on the slow motion gear box adjusters (17mm spanner on my mount, 19mm on more recent ones), then undo the two fixing bolts under each box (8mm spanner) and remove the boxes. Dismantle each box by removing the lock nut, unscrewing and removing the adjuster, then sliding out the drive shaft. (Rotate the shaft to get the worm gear through the threaded hole.) Remove the nylon(?) bushes from the shaft. Degrease, rinse and dry all these parts.

Declination axis

Start by adjusting the mount's latitude to 90° so the dec. axis is horizontal. Undo the 17mm locknut in the middle of the dovetail clamp (you may find a box spanner easier to use than a flat spanner) then unscrew and remove the dovetail clamp casting. Slide off the drive gear, noting the number and size of the plastic washers at each end. The shaft can now be withdrawn from the mount body, with the setting circle, large plastic washer and black plastic centering piece. There is no need to separate the dec. shaft from its conical end piece. Degrease, rinse and dry all these parts.

Right Ascension axis

Adjust the mount's latitude to 0° so the RA axis is horizontal. Undo and remove the 17mm domed nut (box spanner required) and washers, noting their type and fitting order. Slide the shaft out of the mount body, with the drive gear, spacers, washers and other parts. Remove these parts from the shaft, carefully noting their positions. Do not try to remove the shaft from the dec. axis body casting. Degrease, rinse and dry all these parts.

Finally, remove as much grease as possible from the mount body, but without soaking it in degreaser or dismantling it further. A small amount of degreaser on a paper towel is quite useful for this. Note that some plastic washers may still be stuck in place with grease.

Reassembly

At each stage during reassembly you need to check that the various parts turn smoothly but are not loose. Grease can hide any looseness, so it is a good idea to do a "dry run" of each subassembly without grease to make sure everything fits, then dismantle, grease and reassemble.

Right Ascension axis

Smear some grease on the inside of the setting circle and slide it onto the dec. axis body. Grease the shaft. Grease the various washers, the drive gear and other parts, and slide them onto the shaft in the correct order. Put plenty of grease on the teeth of the drive gear. Insert the shaft into the mount body and check that it turns smoothly. Refit the washers and domed nut on the end and tighten.

Check that the shaft turns freely in the mount body, and that the gear turns freely on the shaft. If either of these is too tight, dismantle again and remove one or more of the plastic washers as appropriate, but do not make it too loose. The gear should turn freely on the shaft, but not be able to move along it.

Declination axis

Put the mount's latitude adjustment back to 90°. Grease the inside of the setting circle and slide it into place. Fit the large plastic washer then grease its exposed surface and the shaft. Slide the black plastic centering piece onto the shaft then insert the shaft into the mount. Grease the various plastic washers and the drive gear teeth, then slide them onto the shaft in the correct order.

Screw the dovetail clamp and locknut onto the end of the dec. shaft, but do not over tighten. This needs to be tight enough to prevent the shaft from wobbling, but loose enough to allow the shaft to turn smoothly. When you've got it right, tighten the locknut and check it again. Make sure the drive gear turns freely on the shaft. If it doesn't, try removing one of the plastic washers.

Slow motion drives

Grease the drive shaft each side of the worm gear and slide a nylon bush on each end. Grease the bushes and insert the shaft into the box. Note that the RA and dec. shafts are not inserted the same way round: the RA shaft goes in tapered end first and the dec. shaft goes in tapered end last. Slide the metal adjuster over the shaft (slotted end outwards!) and screw it in, but do not do it up tight. Screw on the lock nut and do it up "finger tight". Smear plenty of grease on the worm gear.

Refit each slow motion drive box to the mount with the two fixing bolts. Gently press the box towards the axis while you tighten the bolts so the worm gear is in close contact with the gear on the axis. Tighten the box adjuster until the slow motion drive becomes stiff to turn, then loosen it very slightly. Tighten the lock nut. Now check the drive turns smoothly while turning the axis through an entire circle. If there are any tight spots, loosen the drive fixing bolts and move the box a little further from the shaft before retightening the bolts.