{"id":4406,"date":"2023-12-26T13:21:00","date_gmt":"2023-12-26T19:21:00","guid":{"rendered":"https:\/\/jonvoisey.net\/blog\/?p=4406"},"modified":"2023-12-26T13:21:00","modified_gmt":"2023-12-26T19:21:00","slug":"almagest-book-x-venus-epoch-position","status":"publish","type":"post","link":"https:\/\/jonvoisey.net\/blog\/2023\/12\/almagest-book-x-venus-epoch-position\/","title":{"rendered":"Almagest Book X: Venus’ Epoch Position"},"content":{"rendered":"

Now that we’ve worked out the mean speed of Venus about the epicycle, we can now determine where it was on the epoch date.<\/p>\n

Ptolemy again uses the observation from Timocharis. He gives the time between the epoch date and that observation as a period of $475$ Egyptian years, $346 \\frac{3}{4}$ days.<\/p>\n

Looking up the appropriate intervals in the mean motion table for Venus<\/a> in the anomaly column, I find an increase of $180;59\u00ba$ which Ptolemy rounds to $181\u00ba$.<\/p>\n

At the time of the observation from Timocharis, we determined Venus to be at a position of $252;07\u00ba$ past apogee. Thus, if we subtract $181\u00ba$ from this, we find that Venus was at $71;07\u00ba$ at the time of epoch.<\/p>\n

Meanwhile, Ptolemy reminds us that the mean position is, based on our model, the same as that of the sun, or $0;45\u00ba$ in Pisces at the epoch time.<\/p>\n

Additionally, the apogee would have moved at the same rate as the precession of the equinoxes ($1\u00ba$ per $100$ years) which means, in that interval of time, it would have increased $4 \\frac{3}{4}\u00ba$ and thus had a position, at epoch, of about $16;10\u00ba$ into Taurus.<\/p>\n

\n

\"\"<\/a><\/p>\n

\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Now that we’ve worked out the mean speed of Venus about the epicycle, we can now determine where it was on the epoch date.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[24],"tags":[25,75,14,69],"class_list":["post-4406","post","type-post","status-publish","format-standard","hentry","category-almagest","tag-almagest","tag-epoch","tag-ptolemy","tag-venus"],"acf":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p9ZpvC-194","_links":{"self":[{"href":"https:\/\/jonvoisey.net\/blog\/wp-json\/wp\/v2\/posts\/4406","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jonvoisey.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jonvoisey.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jonvoisey.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jonvoisey.net\/blog\/wp-json\/wp\/v2\/comments?post=4406"}],"version-history":[{"count":2,"href":"https:\/\/jonvoisey.net\/blog\/wp-json\/wp\/v2\/posts\/4406\/revisions"}],"predecessor-version":[{"id":4409,"href":"https:\/\/jonvoisey.net\/blog\/wp-json\/wp\/v2\/posts\/4406\/revisions\/4409"}],"wp:attachment":[{"href":"https:\/\/jonvoisey.net\/blog\/wp-json\/wp\/v2\/media?parent=4406"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jonvoisey.net\/blog\/wp-json\/wp\/v2\/categories?post=4406"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jonvoisey.net\/blog\/wp-json\/wp\/v2\/tags?post=4406"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}