 |
Aug 3, 2001Here are the encoder mounts that I
finally came up with. The azimuth is very straightforward, just a straight
bracket. The altitude encoder mounting design is copied from Jim's Mobile,
since they were kind enough to put their
fairly detailed installation sheet up on their web site. A $4 sheet of 16
gauge steel, 30 minutes to draw a paper template, and 45 minutes with a
jigsaw with a metal blade, a vice and a hammer (Man, I need to buy a sheet
metal brake someday, this beating on things with a hammer works but what a
pain!) and here we are.
The encoder is in a vertical slot, and the mounting screws in horizontal
slots, so you have full range of motion to perfectly center the encoder.
The mating piece is a piece of steel rod, bent to snake around the split
block hardware, with a shaft collar and setscrew welded on the end. I also
built a small split block to hold the bottom end. It's held in place with a
1/4" bolt with a piece of rod welded on the top (sort of a "wing bolt"),
with a T-nut whacked into the wood from the other side.
|
| Just for your amusement, this was my first arm to the encoder. It worked OK but
wasn't very pretty, and I did see a little bit of inaccuracy on it; I don't know
if it was because of flexing or if the grommet at the pivot point was turning slightly.
|
 |
I got sick of having to thread the wire for the azimuth encoder in
through the hole in the side of the rocker box and reach in and plug it in,
so I picked up a female-to-female phone coupler at Radio Shack,
drilled/filed a square hole in the side of the rocker box, and epoxied it
in. I hooked it to the encoder inside with a 2 foot phone cord also
purchased at RS. |
 |
This is an indoor/outdoor thermometer from Radio Shack. This is sold as
an "automotive" thermometer, so in comparison to their household model,
it's much smaller, black (stylin'), and has a
green backlight which is handy. The left side is ambient and the right side
is mirror temperature. |
 |
This eyepiece rack was a quick project. I'll probably try for
something more intricate or at least with more holes later, but I needed
something to keep me from walking 10 feet for every new eyepiece. |
| Next project is baffling and reducing stray light. First, I
painted the top of the mirror box with Krylon ultra-flat black.
Then I looked down the tube and noticed that you can see a lot of light
around the mirror. So I cut a piece of Kydex to cover the bottom, and cut a
hole an inch smaller than the mirror. Here are before and after, plus a
shot of the bottom. I used a heat gun to help ease the plastic around the
bend in the bottom.
NOTE: after installing this, I noticed that it makes it a little
difficult to adjust the sling tension. I hardly ever have to do this and it
IS still possible so I haven't worried about it.
NOTE: I haven't been able to find Kydex locally. This is actually 1/16th
inch ABS plastic, textured on one side. I've been told that Kydex is a
PVC/acrylic blend. I'm not sure if ABS is better, worse or the same. It
probably only depends on its thermal properties. In the next section you
can see the ABS on top (the new, baffle section) and actual Kydex on the
cage body below that.
The ABS actually looks significantly blacker to me than the Kydex.
|
|
Baffling, part 2
I cut this piece to go around the top. It goes up 5 inches over the top,
which totally cuts off all possible direct rays going into the focusser to
the focal plane.
The narrowest part, just to the right of the cat, goes down flush with
the top of the secondary cage to allow an easy grip for guiding. |