Ad Astra Observatory

I finally decided to bite the bullet and fix the shutter motor. Things went sideways last winter, and I’ve been opening the shutter manually (and tying it shut with rope, so we don’t have a repeat of the wind fiasco).

I knew that the shutter was going to take a bit of doing, so I had been kind of putting it off.

It was a clear, crisp fall day on Saturday, so while I was out working on Trixie anyway, I decided to put in the effort to get the shutter working again.

After reacquainting myself with the problem, I figured out that the main problem was re-stringing the cables properly; there’s a sort of complicated winding thing that happens, and although the cables weren’t completely removed (in which case I would have been very lost) or even tangled, it took a moment to figure out how to maintain tension on them while I was restringing. I got it all figured out, and luckily, it didn’t look like anything was significantly more broken (I originally thought that one of the bearings had jumped out of its seat, but I was mistaken — whew!). Once I got the motor end looking good again, I reattached the cables to the front shutter.

I need to order some new cables, because the current ones are getting frayed, which hasn’t yet caused anything that looks like a strength problem, but is murder on my hands as I’m trying to re-thread the cable seats. I must have half a dozen cuts on my hands from jagged wire bits sticking out. sigh.

I’ve also never been pleased with how the western cable (on the right when I’m inside the dome) runs around the “return” pulley. It’s a long-standing beef. I installed the cable seats incorrectly in the original build-out, and there’s no clear way to fix this problem. But, of all the things, that’s the least of my worries with the shutter motor right now.

The first test of the motors showed something bad was happening — I’m still not sure if it was the eastern cable being too loose on the winding, or whether one of the winding gears was slipping over the shaft, but a bit of tinkering with both of these got the shutter running again.

I’d like to take this moment to say again how proud I am of the shutter limit switches. They work perfectly, every time, and it feels so nice to know that the shutter isn’t going to grind itself to bits by trying to open (or close) too far.

The shutter worked to spec, and I left it alone at the end of the session, proud to have finally fixed the problem.

When I came back out on Sunday, I tried to open the dome, and there was a problem. The eastern cable had jumped off the return pulley, and was in a state where it was too tight on one side and too loose on the other, and I couldn’t get it back on the pulley correctly. The loss of tension had also messed up the winding end, so I figured out which cable needed slack, and tightened the windings to pull more cable in that direction, which left enough slack for me to get the cable run over all the pulleys properly again. 😐 I’ll need to go back in and re-tighten the cables, now that I’ve run the shutter open and closed a few times. More holes in my fingers. sigh.

At the end of the day, however, the dome is fully motorized again, and even automated, if I were ever to boot up the computer and run the observatory again. Maybe I’ll even get to open the shutter with the computer at some point… soon.