Tracing the history of medieval astronomy
One of the long term goals of this project is to collect enough data to derive the orbit of Mars. However, because Kepler didn’t know the orbit of Earth, he couldn’t use the observation on any given night. Instead, he only used observations from when Mars was at opposition1. This happened to be last night, so we packed up the quadrant and headed out.
Continue reading “Data: Stellar Quadrant Observations – 7/27/18 (Mars Opposition)”
It’s been awhile since I’ve posted anything on the Almagest. That’s mostly because I was at a nice stopping point and with the quadrant getting finished up and observations beginning, that stole my focus for awhile. But it’s finally time to jump into Book II. The first chapter in this book is just text. No math. So what does Ptolemy have to say? Continue reading “Almagest Book II: Introduction”
Having finished the quadrant this past weekend, I was finally able to take it out for it’s first light1. A special thanks to Her Excellency Slaine for helping me transport parts that wouldn’t fit in my car as well as Padrig for being my chief observer.
So how’d it go? Continue reading “Data: Stellar Quadrant Observations – 7/20/18 (First Light)”
Before I can start actually measuring the position of stars, I need to know which stars I’m after. In a previous post, I mentioned that I was working on that list, but I’ve now completed that list and have decided to include 500 stars.
The great quadrant is finished.
Continue reading “Instrumentation – The Great Quadrant: Day 12”
When I first started thinking about how an observing team would work, I originally envisioned two people being necessary, with three being ideal. The thought was that one person would use the sight to locate the star as it crossed the meridian, a second would read the observation off the scale aloud, and a third would record it in a log book. If necessary the second person could do the writing.
This division of duties well matches an engraving Tycho had of his mural quadrant:
If we ignore the giant Tycho in the background as this is a heavily stylized image, we see the observer at far right sighting the star, one reading off the time, and a third recording the observation.
However, the past few days I’ve been working on a list of stars to observe and think it may be necessary for my purposes to have even more. Continue reading “Thoughts on an Observing Team”
Today’s project: Finish the scale.
The process on this was very straightforward albeit tedious. At the edge of each line for a degree, I made a slight notch with a razor knife. For each of the 810 transversal dots, I took a small nail and hammered it lightly.
Continue reading “Instrumentation – The Great Quadrant: Day 11”
Today was a much shorter day in part because I’d lost track of time causing a late start and in part because we’re running low on things to do on pieces that don’t currently have paint drying on them.
In particular, getting the scale transferred was one of the larger things remaining. So we started the night by masking off the scale:
Continue reading “Instrumentation – The Great Quadrant: Day 10”
In the last post, we derived equations to demonstrate that the right ascension (α) and declination (δ) of an object can be gotten by knowing four other variables: altitude (a), azimuth (A), sidereal time (ST), and latitude (φ).
In this post, I’ll do an example of using these equations to do just that. For my data, I’ve jumped into Stellarium and selected Altair1 as it’s a nice bright star that I’ll certainly be observing.
Continue reading “Data: Converting Alt-Az to RA-Dec – Example”
Last month, I had a post that briefly introduced the two primary coordinate systems for recording the position of objects on the celestial sphere: the Altitude-Azimuth (Alt-Az) and Right Ascension-Declination (RA (α)-Dec (δ)) systems. There, I noted that Alt-Az is quick and easy to use, but is at the same time nearly useless as objects fixed on the celestial sphere do not have fixed coordinates.
Instead, astronomers1 use the RA-Dec system because fixed objects have fixed positions. My modern telescope does allow for this system to be used rather directly because it has an equatorial mount which tilts the telescope to match the plane of the ecliptic instead of the plane of the horizon. Additionally, it is motorized to allow it to turn with the sky, thereby retaining its orientation in relation a coordinate system that rotates with the celestial sphere. Thus, once it’s set we’re good to go.
However, the quadrants Brahe used were neither inclined to the ecliptic nor motorized. Thus, measurements were necessarily taken in the Alt-Az system and would need to be converted to RA-Dec to be useful. Here, we’ll explore how that conversion works2. Continue reading “Data: Converting Alt-Az to RA-Dec – Derivation”