DIY Wooden LX Wedge
After having determined that the cost of manufacturing my own Aluminium Wedge was going to be prohibitive (the aluminium alone was ~AU$300.00 - and that was the cheap part), and considering the cost of a half decent Meade Ultra Wedge (close to AU$1,000), I decided to go in a different direction. I have read on various web pages that it's possible to manufacture a wedge out of high density marine plywood so I figured why not give that a go! It would be a lot cheaper to buy the materials & manufacture (good old dad is pretty handy when it comes to woodwork) and I might learn a thing or 2 along the way.
All metal fittings are made from stainless steel so as not to interfere with compasses. Much thanks goes to my brother in law, Jason for machining all of the stainless steel & brass bits & pieces.
I designed this wedge based an various DIY designs that I have come across on the web. It's designed for my 8" LX90 however as I'll be using the standard 8" wedge adapter plate, it should also work with other Meade LX90 / LX200 telescopes.
I sourced the plywood from Caporns Pty Ltd in Brookvale. A length of 18mm x 1,000mm x 1,200mm marine grade plywood cost AU$88.
I sourced the various nuts & bolts (all based on the UNC standard & all stainless steel) for AU$70 from Bomond Fasteners in Brookvale (www.bomond.com.au).
In order to ensure a rock solid mount, I decided to use a double layer of ply for the wedge base. 2 pieced of ply were glued together with 2 part epoxy.
If you look carefully at the image above, you can see the circle marked on the surface of the wood with cross lines drawn with a protractor to indicate where to drill the Azimuth / RA adjustment holes. A drill press makes this job MUCH easier as you don't need to worry about the holes being perfectly vertical.
Wedge Side Panels
The above shot shows the wedge sides under construction. To ensure that the side panels were identical during the shaping phase, the 2 pieces of plywood were first screwed together.
I then added the altitude / declination adjustment slot. My main observing location (home in Sydney) is at Latitude 33 Degrees, 45 Minutes South, so to allow for my "infrequent" local travels to dark sky locations outside of the Sydney basin I cut enough play in the slots for 29 - 37 Degrees Latitude.
I should note at this point that the various pieces of wood were cut using a dedicated woodwork bench, in this case, a Triton Workbench. It makes the whole process of cutting and shaping wood much easier than would otherwise be the case.
The partially completed tilt plate with a couple too many holes drilled (the 2 holes closest to the edges). That's what happens when you don't concentrate on what you're doing. Never mind, it adds character.
Attaching the Metal Fittings & Putting it Altogether
I used an old bottle screw from a yacht's shrouding to control the altitude (latitude) find adjustment. The thread pitch is quite fine, so much so that I can adjust the wedge altitude by hand (with the LX90 mounted) although a small spanner would make it much easier.
The azimuth / RA adjustment arm was machined from a piece of stainless steel and provides excellent fine adjustment. A floating piece of threaded stainless is inserted in the hollow section of the "P" piece and held in place by 2 small bolts from opposing sides (above and below). I'll put this into a diagram soon.
The long threaded bar is locked in place by 2 lock nuts on the left hand side and a threaded spacer on the right hand side (kept in place with loctite).
To protect against wood wear, threaded brass bushes were screwed into the wood and used to pass the rods through.
Making sure it Sits OK
The Finished Product
To finish up I removed all of the metal fittings, sanded everything back to a clean finish and applied 2 coats of marine varnish.
Now I just need to wait for the clouds to clear to test it out.