Tracing the history of medieval astronomy
Now that we’ve done a bit of preliminary theory, we’re ready to jump into an example problem. As with before, Ptolemy selects Rhodes at a latitude of 36º. Since we’ve been seeing several of the same diagrams here, I’m going to forego the buildup and give a mostly completed diagram:
Continue reading “Almagest Book II: Calculation of Rising Times at Sphaera Obliqua”
When construction initially began on my quadrant, I had little to go on except the etching of the instrument and my own knowledge of how such an instrument should work. I knew the image came from a work of Tycho Brahe’s, Astronomiae Instaurate Mechanica (Instruments for the Restoration of Astronomy), but at the time was unable to find a translation to see if there was anything I was missing.
Fortunately, a few months ago, I finally located a translation of the vast majority of the book. However, the website seemed to lack the beautiful etchings that should accompany the text. However, scans of the original work were available through the NASA ADS. Unfortunately, being scans of a book over 400 years old, not all of the images were in good condition.
Still, I have worked to piece the text back together with the images, working over the past few months to digitally clean the images, removing smudges and stains, and reproducing the text as a digital copy best matching the original format as possible.
I now provide it as a .pdf for those interested.
In the last post, we proved that two arcs of the ecliptic that are equidistant from the same equinox rise in the same amount of time. In this post, we’ll prove something similar for what happens with arcs of the ecliptic equidistant from the same solstice.
It’s been awhile since I’ve been able to update the blog with anything from the Almagest. As noted in the last post from the book, this section is not one of the better written ones. Indeed, it’s taken me the better part of a month to really work out how the diagram is put together.
Ultimately the trouble stemmed from the fact that it’s not a single diagram; it’s actually two pasted together1, so instead of throwing it all at you at once like Ptolemy did, let’s work through each piece in turn before pasting it together.
To begin, let’s start with a simple celestial sphere:
