Fixing Extra Shoe to SkyWatcher 200P, with screws!

Hi All

After some discussion with Andy T on the benefits of a laser pointer for finding objects, I decided to get one of these. The laser and the bracket are yet to arrive but the extra shoe needed to mount it to the tube, ordered from Harrison Telescopes, arrived in 3 days. This is now fitted with the M4 countersunk screws and black nuts supplied. I will outline the method I used and tools needed, for comparison with Andy’s adhesive-based method (10 March) so you can decide which to use.

1. Make sure you think hard before you decide on the location; drilled holes are permanent. I placed mine about 20mm from the finder-scope shoe, to match the gap between it and the focuser base.

Tools needed

2. Attach masking tape to the area where it is to be attached.

3. Rest the tube horizontal up against a firm support with the focuser aperture above the area to be drilled, to prevent swarf/cuttings getting in. Also, I put newspaper directly under the drilling area to catch any cuttings and masking tape along the inner edge of the stiffener on the end of the tube. Time taken in preparation is well worth it. See the photo below. I would not advise doing this task with the tube in the mount.

4. Mark lines on the masking tape and use the shoe as a template to mark the locations of the two holes.

5. Check that the holes will clear the reinforcing plate (if fitted) inside the tube used for the finder-scope shoe.

6. Tubes are made of thin steel, work-hardened by the rolling process, so sharp drills are essential. Start with a small size drill, say 2.5mm and work up, in steps of 0.5mm, to 4mm diameter. This minimises the force needed to break through initially and subsequently to increase the hole size. Small drills break easily so do not apply too much force, have only a short length of drill protruding from the chuck and try to align the drill radially to the tube.To make sure the drill chuck could not touch and mark the tube, I pushed a rubber tap washer onto the drill, masking tape alone is not thick enough. Make sure you are in a comfortable position and able to control the pressure applied by the drill.

7. After drilling one hole, loosely attach the shoe and check the marked location of the 2nd hole.

8. If the 2nd screw will not insert, increase the hole size of one hole, or both if needed, to 4.5mm. Mine were fine with 4mm diameter.

9. Remove masking tape and the paper inside the tube and attach the shoe. I used a small spanner (shown in photo) to hold the nuts while tightening. Take care not to shear the screws as they have a small cross-section and not to scratch the black paint inside the tube.

Hold nut with small spanner
Job done

Once the bracket and laser arrive I will post a photo of the finished assembly, soon I hope!

Have now fitted bracket and laser but not used it yet. It was quite a loose fit into the shoe dovetail (left in view below) so needed a small aluminium shim. The SW finder bracket is not a brilliant fit either but at least it tightens up before the clamp screw runs out of thread. I think it looks the part at least (see below).

Total outlay for all 3 parts was about £25, all bought separately off ebay.

Paul

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