In the next chapter, Ptolemy gives some configurations of stars that he considers important. These are in addition to stars being on straight lines with one another which we encountered previously. He outlines three general categories. Continue reading “Almagest Book VIII: Configurations of the Fixed Stars”
The Ptolemaic Zodiac Project
This past year, while working on researching the history of Ptolemy’s star catalog, I came across the following quote from Toomer:
Ideally one should provide a reconstruction of the outline of each constellation as it appears on Ptolemy’s star-globe. Unfortunately no one has done the necessary work of assembling and comparing all the literary and iconographic evidence from antiquity and from the derivative Arabic tradition (notably as-Sufi). This would be an interesting and valuable enterprise.
Essentially what Toomer is noting here is that, while historians of astronomy have spent considerable time trying to reconstruct what stars the catalog described, less attention has been paid to how the constellations looked.
Thus, I’m launching a spin-off from my main project to look at this topic. Continue reading “The Ptolemaic Zodiac Project”
All Done with Gulf Wars XXXI
The past month has been rather quiet here in the blog, but there was quite a bit going on for me behind the scenes due to Gulf Wars. This was largely due to the number of classes I taught. Continue reading “All Done with Gulf Wars XXXI”
Data: Stellar Quadrant Observations – 2/17/2023
It’s getting to that time of year where the weather becomes extremely unpredictable. Warm enough to have the windows open one day and an ice storm the next.
Despite it being cold this past Friday night, the sky was at least clear with no wind so Yseult and I went out to do some observing. Continue reading “Data: Stellar Quadrant Observations – 2/17/2023”
Gulf Wars 2023 Class Schedule
I’ll be teaching six classes at Gulf Wars this year. Information is below the fold! Continue reading “Gulf Wars 2023 Class Schedule”
Almagest Book VIII: On the Construction of a Solid Globe
Having laid out the general structure of the milky way, Ptolemy next describes the process of “the construction of the solid globe and the delineation of the constellations”. Continue reading “Almagest Book VIII: On the Construction of a Solid Globe”
Almagest Book VIII: On the Location of the Milky Way
Having laid out the star catalog, Ptolemy next faces a somewhat more abstract challenge: attempting to describe the nebulous structure of the Milky Way. He first describes the general shape and color:
Now the Milky Way is not strictly speaking a circle, but rather a belt of a sort of milky colour overall (whence it got its name); moreover this belt is neither uniform nor regular, but varies in width, colour, density and situation, and in one section is bifurcated. [All] that is very apparent even to the casual eye, but the details, which can only be determined by a more careful examination, we find to be as follows.
There’s not really much to discuss here, so instead, I’ll combine Ptolemy’s descriptions with some screenshots from Stellarium to help highlight what he’s talking about.
Continue reading “Almagest Book VIII: On the Location of the Milky Way”
Scholarly History of Commentary on Ptolemy’s Star Catalog: The Aratus Latinus & Codex Climaci Rescriptus
In a previous post, we discussed a bit about Aratus’ poem, the Phaenomena, to which the Aratus Commentary was a response.
What I haven’t mentioned yet is that this original poem is still around. In fact, we have numerous copies of it thanks to it exploding in popularity in the $8^{th}$ century. However, sometime before then the poem itself had evidently been padded with other astronomical works. Among them were some descriptions of constellations. And these descriptions would provide new insight to our conversation. Continue reading “Scholarly History of Commentary on Ptolemy’s Star Catalog: The Aratus Latinus & Codex Climaci Rescriptus”
Scholarly History of Commentary on Ptolemy’s Star Catalog: Stars at the Southern Limit
Another argument over the authorship of the star catalog examines the stars near the southern horizon. Since Hipparchus observed from Rhodes with a latitude of $\approx 37º$ and Ptolemy from Alexandria which is $\approx 31º$ N, this means that Ptolemy could have observed starts $5º$ further south that were never above the horizon of Hipparchus.
However, Delambre notes that there’s not a single star in the catalog that could not have been observed by Hipparchus at his latitude. So if Ptolemy was the originator of the catalog then, for some unknown reason, he declined to observe stars near the horizon1.
Thus, the inclusion or exclusion of stars cannot settle the matter. But astronomers have turned to other questions regarding stars near the southern horizon to approach it. So in this post, we’ll explore three papers on this subject. Continue reading “Scholarly History of Commentary on Ptolemy’s Star Catalog: Stars at the Southern Limit”
Scholarly History of Commentary on Ptolemy’s Star Catalog: Proper Motion Analysis
Finally, in the discussion of Ptolemy’s star catalog, we’ll be moving beyond Grasshoff2.
In this post, we’ll explore a new technique, first considered in the late $1980$’s to use high proper-motion stars to attempt to determine the epoch of the star catalog. Continue reading “Scholarly History of Commentary on Ptolemy’s Star Catalog: Proper Motion Analysis”