It has been seven months since I have done any observing. Between unfortunate weather during good moon phases this summer, being exhausted from mundane life things, running an event… it just didn’t happen.
But now that a lot of that is behind me, we had a crisp fall night with daytime temps in the 60’s and lows in the 40’s. Chilly, but entirely manageable. Especially since I purchased a heated vest last winter. I’ve been looking for a pair of heated pants to go with it, but haven’t found any with sufficiently good reviews at a decent price just yet.
Yseult joined me again, and we got through 60 observations.
In those observations, eight of them were new objects including much of the constellation Delphinus, a few in Taurus, and one in both Auriga and Orion.
When processing the data, it was quickly apparent that the azimuth ring was misaligned. This is often one of the hardest parts of setting up as it’s something that gets done once and affects the measurements for the rest of the night. In specific, the Azimuth tended to be about 2.3º low. Some of this was that we aligned on the north star which was at its greatest distance from true north at that time (about 0.8º). Some can also be explained by the fact that Yseult and I both aligned on the north star and we took an average of the position on where to set the azimuth ring. However, the quadrant arm itself can wiggle in azimuth by a degree or more as the wood the axle goes through is slowly wearing. We each have a consistent technique we use so that we always do things the same way, but our techniques are actually different. And since Yseult was the sole observer for the night (I just recorded the observations), that certainly threw it off some too. Ultimately, just adding 2.3º to each observation put them right back into the sort of distribution we’d expect.
As always, the data is available in the Google Sheet.
I also spent at least 15 hours working on my paper this weekend. While working on the new paper updating Ptolemy’s lunar model to present day, I found the solar model was giving surprisingly inaccurate results. I checked the math yet again, and everything seemed correct, but believe the error was due to making use of Ptolemy’s table of the sun’s anomaly. I’d adopted it without giving due consideration to whether or not the underlying conditions had changed since Ptolemy’s time and indeed they had. Specifically, that table is forms based on some geometry mostly based on the distance between the earth and the center of the eccentre which changed from about $2.5^p$ for to $2.1^p$ in the reworking. Thus, the effect of the anomaly should be smaller.
I’ve reworked this table now and am working on the updated version of the paper, but we’ll have to see how much it helps.