This weekend was Crucible at the Crossroads here in my home Barony of Three Rivers. I taught two classes, one on a general overview of medieval astronomy, and one introducing practical observational astronomy. In addition, it was the autumnal equinox on Saturday, so some minor adjustments were made to the quadrant to allow for solar angle observations. Lastly, I was called up in court for a few awards related to the project.
More on all of that beneath the fold.
A week ago, the weather for Crucible was looking very iffy. The remnants from hurricane Florence were expected to cause storms throughout the entire event. But as the event crept closer, the forecast continually improved, first clearing out rain on Saturday evening, then the entire day, then none Friday past noon, and finally none Sunday either. But the front brought through Friday morning did cause temperatures to drop from the consistent mid-90’s, to pleasant temperatures in the 70’s; in other words near perfect camping weather.
Saturday morning I taught my new class which is a general overview of medieval astronomy1. The intent had been to start with Ptolemy as Greek astronomers are in that fuzzy period that some consider to be outside the purview of SCA focus. However, Platonic ideals were so fundamental to later thinking I quickly realized I would need to include Plato, who was one of the earliest Greek astronomers. Thus, skipping several hundred years of history to jump from him to Ptolemy seemed odd and a smattering of notable Greeks did make the cut.
From there, we went through an outline of Ptolemaic astronomy (without getting into any details from the Almagest), the vanishing of scientific astronomy from the West, the preservation in the Islamic world, reemergence in the West, Copernicus, Brahe, and finally Kepler.
I hope to eventually polish this class and get a recording of it, but as this was the first time, I didn’t see any reason to do so at this time. That being said, the class went well.
Once the class was over, I headed over to the quadrant I’d set up the night before to make a few quick modifications to allow us to determine the altitude of the Sun as it crossed the meridian. Since looking down the sights at the Sun would be a bad idea, I attached a piece of pipe to the sighting arm, and a piece of a paper plate behind it2.
The idea here is very similar to what I’ve done in the past with my telescope when doing solar viewing. As it’s an even worse idea to look at the sun through a telescope but quite difficult to find the sun with the solar filter on, I first align the scope by trying to minimize its shadow, then removing the eyepiece and letting the image project onto the ground. The telescope would then be locked, the filter placed on, and the eyepiece reinserted. Here, the tube played the role of the telescope body. When its shadow was a circle with the sun shining straight down it, the instrument would be aligned.
However, the thick grass made it hard to clearly see the shadow, hence why a piece of paper plate was used as a better focus for the shadow3.
The result was an angle of 51.3º. Jumping back to when I used another instrument to find the solar altitude at the summer solstice, I’d then found an altitude of about 75º. Thus, the difference is 23.7º. This is slightly high as it should be 23.4º.
Looking a bit more at each of the two figures I’d gotten, the one from the summer solstice was 75º whereas the true value (via Stellarium) should have been 74.8º. For the autumnal equinox observation, we got an angle of 51.3º where the true value was 51.3º. This is another affirmation that the quadrant is particularly well crafted as this reading came correct to the number of significant digits it can read4. The solar angle dial was obviously much smaller and, as it didn’t read to fractions of a degree, it’s not surprising that that was the source of the discrepancy. Hopefully, weather will continue to cooperate and I can continue to use the quadrant for these observations at additional solstices and equinoxes in order to continue to improve the accuracy.
There was a bit of cheating on this observation, however. Whereas for the previous observation, I’d aligned the instrument on north, clouds the night before prevented me from being able to sight the quadrant on the north star as I often do. While I could have used the same method as I’d done for the summer solstice to find north, there wasn’t a particularly good way to use the shadows given the aforementioned thick grass. I considered using the surface of the quadrant’s base with the central column as the gnomon, but I felt it would be too large to give the crisp shadow I needed since its shadow would change as the angle of the sun did.
So instead, I had looked up what time the sun should cross the meridian in Stellarium, and simply took the reading at that time.
Although I didn’t write a post on it, the quandrant was taken to Queen’s Prize last weekend. For the non-Calontiri, this is a novice A&S competition that’s less competition focused. It’s meant more as a way to get feedback from experts as well as to show off, inspire, and be inspired. This5 apparently gained this project quite a bit of attention during court at Crucible, I was given not one, but two awards related to it.
The first was a baronial award from Baroness Gwendolyn: invitation to the Baroness’ Order of Patronage. The second was a kingdom level AoA science award, a leather mallet. The scroll for the former was done by Mistress Slaine, (who was my sponsor for Queen’s Prize)6.
This scroll is absolutely phenomenal and has many subtle elements worked into it. The device of the Barony is worked into the hills. The layout of the stars is correct for the night this was given. The two pets are ones of Gwendolyn’s that unfortunately passed away this year. Lastly, as Slaine told me, “That’s no moon.” Indeed, the moon bears a strong resemblance to the second death star from Return of the Jedi.
The scroll for the leather mallet was a preprint, but was painted by Her Excellency Konstantia who has a way of turning simple outlines into magnificent artwork7.
The picture8 really does not do this scroll justice as the paints she used have powdered amethyst in them giving it a brilliant sparkle in direct sunlight.
That evening, I taught a second class that was intended to be a mix of understanding stellar coordinates, the night sky, and how to use the quadrant to get from the latter to the former. However, the clouds poured back in and despite having a very nice conjunction of planets that neatly demonstrates the ecliptic right now, they were all blocked from view making things much harder to discuss. However, there were enough breaks in the clouds, that we were able to do a few practical demonstrations with the quadrant. Although nothing in particular was on the meridian, we unlocked the rotation and allowed participants to site Mars or other bright objects.
But by 10pm, the sky once again cleared and I collected a group of interested participants to go do some actual observations. The data is below:
| Object | Alt | Az | ST |
| β Aqr | 46.1 | 180 | 21:34:00 |
| γ Cap | 34.9 | 180 | 21:40:39 |
| ε Peg | 61.4 | 180 | 21:45:00 |
| δ Cap | 36.5 | 180 | 21:47:30 |
| θ Peg | 57.4 | 180 | 22:11:10 |
| α Aqr | 51.0 | 180 | 22:05:00 |
| ι Peg | 77.5 | 180 | 22:13:30 |
| δ Cep | 70 | 0 | 22:23:00 |
| γ Aqr | 50.5 | 180 | 22:23:00 |
| π Aqr | 53.0 | 180 | 22:27:30 |
| ζ Aqr | 51.8 | 180 | 22:29:50 |
| ζ Peg | 62.4 | 180 | 22:45:30 |
| α PsA | 22.0 | 180 | 22:58:30 |
| β Peg | 79.1 | 180 | 23:08:10 |
| α Peg | 66.4 | 180 | 23:08:40 |
| α UMa | 10.5 | 0 | 23:12:52 |
| φ Aqr | 45.3 | 180 | 23:17:00 |
| γ Psc | 54.7 | 180 | 23:18:10 |
This observing run made a small change to our approach. Whereas previously we’ve chosen stars by using the list from the observing program, after a few observations, we started simply choosing whatever stars we could see as there was a near full moon washing most out. We then used Stellarium to determine which stars they were. This ended up meaning we observed a few stars that weren’t previously on our list.
Comparing this to the true values for these objects, tonight’s average error in declination was 0.24º which is about 14.4 arcminutes. This is notably higher than previous observing nights, but when averaging the declination error for all observations over all nights we’ve observed, it’s 0.11º or 6.6 arcminutes which is similar to the smallest division on the quadrant’s scale.
For this run we also had an average error in the RA of -0.41º which indicates we’re taking observations about a minute and a half early. Likely because we’re a bit anxious, waiting for stars to come to us. Still, the error in RA is notably smaller than the error in declination.
Meanwhile, all the data has been added to the program I’ve written and here’s how that star map is looking so far9:
We’re starting to pick up multiple observations of some stars which is why a few have error bars10.
Thanks to Padraig and Konstantia who were my assistants for the majority of the night.
- Thanks to Rima for the picture.
- Thanks to Amy for this picture.
- Amy again took this picture.
- This in turn stresses how much of the error for stellar and planetary observations is due to observational error as sighting faint stars is much harder than the Sun.
- As well as award recommendations from friends, I’m sure
- The picture below was taken by Slaine and is shown out of the frame.
- Konstantia has a post about preprints on her blog here.
- This picture was taken by Konstantia as she finished the scroll, which is why the name and date isn’t filled in or the scroll signed. It was simply luck that I received hers.
- Keep in mind that this chart is flipped right-to-left as RA-Dec is set up as if we’re viewing things from outside the celestial sphere instead of inside.
- The error bars are based on the standard deviation of the values and are not being compared with the true values in any fashion.