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Pseudo-Ptolemy’s Treatise on the 9 Types of Comets

Starting around the 13th century, various astronomical texts began making their way into Christian Europe. These texts were largely translated from Arabic.

Among them, was a text that was originally attributed to Ptolemy which discussed the character and astrological implications of comets. Scholars have since concluded that this text is not by Ptolemy, but it was still widely distributed.

This text is one of many that is under investigation for the Ptolemaeus Arabus et Latinus project. There they provide a scan of a manuscript in the collection of the British Library (Sloane 2030) as well as a transcription of the text.

However, there was no translation. As such, I have attempted my own which is placed below the fold.

Continue reading “Pseudo-Ptolemy’s Treatise on the 9 Types of Comets”
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Posting Will be Slow

Work on the Almagest is going to be slow for me for the next several months. The particular portion that follows the last post is especially challenging because Ptolemy repeats the long procedure he just went through over the course of the last five posts, in an iterative manner. However, he doesn’t show any of the work – just the final results. Thus, it’s going to take me a long while to get through all of that to post about in the first place.

But on top of that, I’m the event steward for two events in my barony in the next year as well as helping with others. Thus, a lot of my free time has been devoted to those.

Hopefully, I’ll find some time here and there to work on this project, but it will certainly be slow.

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Almagest Book X: Correction for Equant – Third Opposition

In the previous two posts, we’ve been looking at how the apparent position of the center of a superior planet’s epicycle shifts position along the various circles. Specifically, we’ve been looking at how the angle between oppositions differs between the eccentre of mean distance and the equant circle.

In this post, we’ll do the same for the third opposition Ptolemy gave us. Unsurprisingly, the process will be largely the same as in the past two posts. Continue reading “Almagest Book X: Correction for Equant – Third Opposition”

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Almagest Book X: Preliminary determination of Mars’ Apogee & Eccentricity – Part 2

In the last post, we began the process of determining Mars’ eccentricity and the position of apogee. The technique is fundamentally similar to the three eclipse method used for the moon, but the presence of the equant is throwing a wrench in things.

Specifically, right at the beginning of the last post we had to make an assumption about $\angle BDG$ that we know was incorrect. We’re not quite ready to address that, but for now we’ll work on finishing finding the line of apsides as well as the eccentricity as if that assumption were correct. Then, in future posts, we’ll go about trying to iteratively correct that assumption. Continue reading “Almagest Book X: Preliminary determination of Mars’ Apogee & Eccentricity – Part 2”