Meade standard wedge mod's

September 10, 2009

Yeah, my telescope has made it here from Colorado.  I've set it up in my office to have a look, and my initial impression is that it is very sturdy and well built.  I can't wait to get it outside!

I was able to set up the telescope tonight and have a look at Jupiter with it...so cool.  The wedge was relatively easy to setup, however I do not yet have the hang of using it to get my polar alignment correct.

Well, I've had a month and a bit to assess the wedge, and I have come to the following conclusions:

1. Hex keys are needed to adjust the fasteners on the wedge.  This seems kind of finicky in the dark.

2. The latitude fine adjustment mechanism is flimsy, and again you need a hex key to adjust it.

3. There is no fine adjustment mechanism for azimuth.

4. The latitude scale on the side of the wedge is not very useful.  The reference for reading it (according to the manual) is the center of the 1/4-20 machine screw, which is pretty much impossible to read with any kind of precision.  Also, after using a digital protractor I discovered that the angle scale, which is essentially a sticker, is out of position by at least a whole degree.

These deficiencies have made my polar alignment learning curve much steeper, and so in the interest of making my life easier, I intend to fix them.  Stay tuned!

Item #1 on my wedge wish list was an easy fix.  I took the kids on the weekend and went out to Lee Valley Tools  here in town to get some 1/4-20 screws with large plastic knobs for $1.80 each (Lee Valley jig & fixture parts - round knobs).  Now there's no need for hex keys to adjust the wedge...tada!

Many commercially available wedges have a beefy bar across the wedge against which the latitude adjustment screw pushes.  Several people I've found online have come up with similar setups on their own.  My version uses a piece of 1" dowl, 3 1/4-20 tee nuts, two 1/4-20 x 2" bolts, and one 1/4-20 4" eye bolt.  I drilled a hole in either end of the dowl to clear the 2" bolts, and then cross drilled a hole in each end to accept the tee nuts.  I then drilled, at a convenient location along the length, a hole for another tee nut and a cross hole for the eye bolt.  To install I simply used the 2" bolts through the tee nuts in the ends to secure it in the bottom of the already existing slot in the side of the wedge, then the eye bolt screwed in through the other tee nut to push against the underside of the wedge top plate.  Screwing the eye bolt in and out makes the telescope go up and down.  I found this very simple and quick to put together, and it works great!

My idea for how to move the wedge around on the top of the tripod changed numerous times since I first started thinking about it last fall.  The idea I went with in the end is a simple turnbuckle link between the tripod base and the wedge.  I used simple 1/4-20 hardware, a drill, and a 1/4-20 tap for the job.  On the wedge side I drilled a 1/4" hole down through the base of the wedge on the left-hand side.  On the underside I bolted a 1" long 1/4-20 union nut, and then on the underside of that I bolted one end of the 5" long 1/4-20 turnbuckle.  I filed the end of the union nut a bit so it fit snuggly into the eye of the turnbuckle.  On the tripod side I drilled a pilot hole in the side of one of the leg stop blocks opposite where I just installed the turnbuckle on the wedge (these are solid aluminum by the way!), and tapped it with a 1/4-20 thread.  I screwed a 1/4-20 eye bolt into the newly tapped whole, with some thread lock to make sure it doesn't loosen.  I then bolted the eye bolt to the free end of the turnbuckle.  Done.  Pictures of my completed setup are below.

After I made the first three mods, I found that it was now dead easy to polar align using my finder scope.  I don't even bother leveling my tripod or setting the correct latitude.  I just adjust the azimuth and latitude with my fancy-shmancy fine adjusters while I look through the finder scope.  It takes like 30 seconds.  Of course my finder scope aim has to be good, and my declination setting wheel has to be setup correctly.  I haven't bothered to do anything to correct the latitude scale on the wedge.

After using my setup a few times, I found a couple of things that needed tweaking.  The worst was that as you turn the eye bolt, it tends to walk along the underside of the top plate.  At one point it walked to the side enough that it buckled, and the telescope went clunk.  Argh!  To fix this I screwed a wooden block on the underside of the top plate to make a pocket that the eye bolt can't walk out of.  The other thing needing tweaking is the end of the eye bolt, by itself, chews into the aluminum casting of the top plate.  I tried a nylon nipple thingy, a wood thingy, and a glob of epoxy, all of which eventually ground off.  My final solution was a 1/4-20 nylon acorn nut screwed on the end.  This seems to be standing up okay.

I also found that the hand knobs I had on the wedge were hard to tighten with my hands, so I changed them for big beefy ones that I found at Home Depot.  Now it works sweet!

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