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Notes on this chart are given below:

Galileo's horoscope drawn by himself

Notes on this chart

By Deborah Houlding

The sheet begins with two lines that relate to Galileo's time of birth. It is usually (incorrectly) reported that he was born on the 15th February (Julian Calendar), but as Nick Kollerstrom explains in his accompanying article this would only be correct according to the old convention of denoting the date from the previous sunset, by which 22:30 hrs of 15th Feb (top line) relates to 3:30 pm of 16th February 1564 (second line) according to modern convention. On the second line both 3:30 and 4:00 pm are noted, suggesting that Galileo was working within this time bracket to establish his correct horoscope. Neither of the two horoscopes shown relate to these local times, but the bottom one (with the ascendant at 14°33 Leo) is very close to what we would obtain by a computer for at time of 3:45pm (LMT) on 16th Feb 1564 - Galileo may have taken the intermediate time between this time range as a 'base chart' from which to start his rectification. He has also noted at the top of the page the latitude for his place of birth: 42°30' - the actual latitude of Pisa, Italy, is 43N43, but Galileo was probably working with tables of 'rounded' latitudes to explain this discrepancy.

The next part of the sheet displays a table that indicates the noon positions for the planets on the 15th and 16th February 1564, by which Galileo has calculated their average daily motion - required to obtain their actual positions in the charts.

Down the left hand side Galileo has listed the longitude positions for the planets that have been inserted into the charts. These are the same for both charts with the exception of the Moon, which is located at 4°40' Taurus in the top chart and 4° 47' Taurus in the bottom chart, agreeing with this table. Alongside the Sun and Moon is written vel, referring to velocity and indicating that the Sun and Moon are swift in motion.

The remaining planets are noted as either direct (D) or retrograde (R) in motion; northern or southern in latitude (M. stands for meridional, the term used for planets with northern latitudes, S. stands for southern); ascending (A) or descending (D) in latitude - and then their latitude is listed.

Although the bottom chart, by its location on the sheet, could be assumed to be a correction to the top chart, it is more likely that this was Galileo's original chart because the Part of Fortune, which is marked on both charts at 12°31' Libra is only correct for this chart. The top chart, with the ascendant at 21° 37' Leo should have the Part of Fortune at 19° Leo. Galileo has apparently calculated the position of the Part of Fortune for the earlier chart and then inserted that position into the chart for the later time, overlooking the fact that a shift in the ascendant would affect a shift in the position of the Part of Fortune. Along the left hand side, the Part of Fortune is noted as falling in Libra; underneath that Galileo has noted "Dom Venus", which at first glance appears to refer to the Part of Fortune being ruled (ie, dominated) by Venus - but if we consider the 'Animodar' method of rectification that was popular in his period, this could be offering an important clue as to why the ascendant was rectified to agree with the degree position of Venus.

The Animodar method of rectification aims to correct the degree of the ascendant, once the astrologer knows which sign should be on the ascendant. The method is based upon consideration of the degree of the previous syzygy (lunation). Reduced to its basic principles, if the chart was preceded by a new Moon, it considers which planet has the most essential dignity at the degree of the New Moon; if it was a full Moon it considers which planet has the most essential dignity in the degree of the luminary above the earth.

The previous lunation in Galileo's chart was a new Moon (on 12 Feb) at 2°53 Pisces. The planet with the most essential dignity at that degree was Venus, which ruled the sign by exaltation and the degree by term. The Animodar method states that the angles should be corrected to agree with the degree position of the planet which dominated the previous syzygy - hence it appears that Galileo has attempted to rectify his birth chart to 21°37 Leo by this method, to concur with the degree position of Venus, which he has calculated as 21°37 Pisces. (For more information on the Animodar method of rectification see the glossary entry).

This worksheet is obviously unlikely to have been intended as his final presentation and his information relating to the fortitudes and debilities of the planets is incomplete. It contains only the calculation for Mercury, (along the left hand side of the lower chart), which may have been a planet of particular interest to him if he was considering his own financial prospects, because of its opposing position to the Part of Fortune and rulership of the 2nd house cusp. Mercury's fortitudes are listed first and it is given 2 points for falling in its own terms and 4 points for being direct in motion. However, it loses 5 points for being in its sign of fall (exilio), where it opposes its own sign of exaltation; 4 points for being in its sign of detriment (Deject.); 4 points for being under the Sun's beams (oppress. - he uses the term liber, ie, 'liberated' where planets are free from the Sun's beams); and 2 points for being oriental of the Sun. In total Mercury therefore has only 6 points of fortitude and 15 points of debility, making this planet weak with a numerical score of - 9.

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D. Houlding, 2004