The hope was that this would be another triumphant post, with a list of all the stars that Padraig and I got last night. Instead, I’m sad to say that the quadrant is temporarily out of commission.
One of the issues with transporting the quadrant is that the center column is about 9 ft long. I drive a Subaru Forester which has the space, but it needs to rest on the dashboard right above the hazard lights button. Quite often when I take it out, it presses the button. This typically isn’t a big deal, but as there was someone else observing at Brommelsiek last night who might be taking astrophotos, I wanted to be courteous and turn them off as quickly as possible. So I stood the center column up against the open trunk and turned them off.
I’m not sure if it was the wind or my closing the car door, but the center column fell over onto the cement. A quick look and I didn’t see any damage and started setting up. In doing so, I saw the first signs of trouble.
The quadrant arm hangs from a steel pipe and is then secured on by a pipe cap. A hole has been drilled through the cap and the tip of the pipe through which a bolt is placed for the plumb bob to hang from. When I was setting this up, I noticed that the hole wasn’t vertical as it should be. It was slightly off to one side. I attributed this to not screwing the pipe cap on correctly and after a bit of fiddling with it, I got it to lay how it should.
As we used the instrument, we noticed that the arm wasn’t swinging as smoothly as it usually does. We attributed this to the high humidity last night, potentially causing things to swell a bit and pressed on.
When taking it down, we realized that what was really causing the sticking was that the arm wasn’t rotating on the pipe, but was sticking to that, and turning the pipe slightly. This meant that the bolt for the plumb was no longer hanging directly in the center of the column. Instead, it could be off to one side by as much as 3/8″. This could introduce a large amount of error since a single degree on the scale is not much larger than that.
This immediately jumped out at me as I began processing the data this morning. To illustrate, I’ve left what I did process below.
| Object | Alt | Az | RA | Dec | Dec Error1 |
| γ Gem | 67.6 | 180 | 6:38 | 16.32 | -0.08 |
| α CMa | 34.75 | 180 | 6:42 | -16.53 | +0.20 |
| ξ Gem | 64.75 | 180 | 6:47 | 13.47 | -0.58 |
| ο1 CMa | 27.7 | 180 | 6:50 | -23.58 | +0.60 |
| θ CMa | 39.8 | 180 | 6:54 | -11.48 | +0.56 |
| ε CMa | 22.8 | 180 | 6:55 | -28.48 | +0.50 |
| σ CMa | 24.4 | 180 | 6:56 | -26.88 | +1.05 |
| ο2 CMa | 28.05 | 180 | 7:01 | -23.23 | +0.61 |
| γ CMa | 36.05 | 180 | 7:03 | -15.23 | +0.40 |
| δ CMa | 25.65 | 180 | 7:05 | -25.63 | +0.77 |
| ω CMa | 25.3 | 180 | 7:12 | -25.98 | +0.79 |
| δ Mon | 50.8 | 180 | 7:12 | -0.48 | +0.02 |
| π Pup | 15.3 | 180 | 7:16 | -35.98 | +1.12 |
| τ CMa | 26.05 | 180 | 7:20 | -25.23 | +0.28 |
| λ Gem | 67.35 | 180 | 7:21 | 16.07 | -0.47 |
| δ Gem | 72.0 | 180 | 7:22 | 20.72 | 1.26 |
Here, we can clearly see that the error in Dec is varying far more than normal and averages about 0.5º high indicating that the pipe was turned counter-clockwise relative to its normal vertical position, which is precisely how found it at the end of the night.
This afternoon, I took a look to see why the pipe was turning.
Here, you can easily see that there’s a big nick in the wood at the upper left. That’s merely cosmetic. But at the seam along the right, to the right of the cap, we can see that the board the pipe goes through is pulled inwards. So it looks like the glue broke when it fell, and the pressure of the pipe caps pressing in on it distorted it, by a fraction of a millimeter. But that was still enough to allow the pipe to rotate easily enough to turn by hand.
Here’s the position the pipe was in. Note that the holes aren’t at all aligned with the column.
The hope was that this would be an easy fix so I stuck a washer behind the cap to make up for that mm and tightened it back down again.
Unfortunately, the wood just can’t hold up under the pressure. There’s now a crack in the layers of the plywood on the left and a much more pronounced dip on the right. It’s also separating along the top.
At this point, the pipe is holding tightly, but as the wood fatigues it will surely loosen again. Thus, this portion is going to need to be redesigned. Hopefully, I can get this done by Gulf as I was planning on taking it there to observe a slightly different sky!