The terms oriental and occidental have caused a fair bit of confusion in the astrological tradition as these words have been used for planets in quite different situations. Unfortunately, texts quite frequently fail to explain what their definition of the term is.
In the introduction to his translation of Bonatti's Book of Astronomy Ben Dykes sets out three different ways in which astrological literature used the terms oriental and occidental:
1. Planets are ?oriental? if they rise visibly before the Sun, and ?occidental? if they set visibly after him. This is similar to the modern understanding, since to rise visibly before the Sun means at least to be in an earlier degree. There were differing opinions on the longitudinal interval a planet had to be in, and whether the intervals were of equal significance.
2. Planets are ?oriental? if they are in the ?eastern? quadrant between the Ascendant and Midheaven ( i.e., where the Sun rises) or the one opposite to it, and ?occidental? if they are on the ?western? quadrant between the Midheaven and the 7th ( i.e.,when the Sun sets) or the one opposite to it.
3. Planets are ?oriental? if they currently , or within 7 days before or after the nativity , are rising out of the Sun?s beams and will become visible at sunrise or sunset; they are ? occidental? if they currently , or within seven days before or after the nativity, are sinking into the Sun?s beams and will become invisible at sunrise or sunset. In Hellenistic astrology this is an example of of what is called ?making a phasis? , and the distance from the Sun at which this arising or sinking would happen, was standardised at 15 degrees. According to this definition , the inferiors can be ?oriental? ( or pertaining?to-arising) on either side of the Sun, since they can arise both while going direct and on their retrograde path.
(Book of Astronomy, Guido Bonatti, translated by Benjamin Dykes, 2007, page Ixxxii-Ixxxiii)
The first defintion is probably the most common in the medieval and renaissance tradition. Ptolemy also offers us the second definition which relates back to planetary sect. Hence the first quadrant from ASC-MC is masculine, the second from MC-DESC feminine etc. The third definition is found in Paul of Alexandria. Benjamin Dykes has concluded that Paul's definition was the basis for the medieval innovation of differentiating between planets being 'combust' as opposed to simply 'under the beams'.
Looking at the Skyscript Glossary under oriental/occidental it appears the terms have even more uses in the tradition!
If a planet is described as 'oriental in the figure', it means that it is located near the ascendant which is the eastern angle, whilst 'occidental in the figure', means that it is located near the descendant which is the western angle.
Occidental hemisphere is the western/setting hemisphere, incorporating the 4th, 5th, 6th, 7th, 8th, and 9th houses.
Oriental hemisphere - the eastern/rising hemisphere, incorporating the 4th, 3rd, 2nd, 1st, 12th, and 11th houses.
http://www.skyscript.co.uk/gl/oriental.html
http://www.skyscript.co.uk/gl/oriental.html
The best discussion I have seen of the quadrants is in the 2nd edition of Deborah Houlding's book Houses: Temples of the Sky. If you haven't already got this book I highly recommend it to you.
In terms of the three definitions of the term above we can see:
Definition 1: In the example chart you have given us Venus is occidental of the Sun as it will not rise before the sun but will be visible in the night sky after the Sun has set later that day.
Definition 2: Venus is in the example chart is located in an occidental quadrant ie opposing the quadrant MC to DESC which is also occidental.
Definition 3: Venus in the example chart will not meet the definition provided by Paul of Alexandria. Although Venus is occidental of the Sun in terms of being a visible night planet this still doesn't meet Paul of Alexandria's definition. This is because Venus will not fall under the sun's beams or ''make a phasis'' and become invisible at sunset within the next 7 days. Generally, hellenistic astrologers used a standardised orb of 15 degrees from the sun to establish this. However, some astrologers use software to calculate exactly when a planet falls ''under the beams'' or becomes rendered invisible by the Sun in a particular locality.
Mark