Papers of John Guy Porter

A copy of Porter's script for 'The Night Sky in September' on Mars at opposition in Aquarius on 12 September; Mars and the Earth at the closest approach on 6 September and how this happens; the unfavourable angle of Mars for northern hemisphere observers and the best work being expected from southern hemisphere observatories; conditions for a really close approach being best in August and September, when it is mid-winter in the northern hemisphere of Mars, the southern hemisphere thus being the better observed; the measurement of right ascension eastwards, with reference to the First Point of Aries and the Greenwich Meridian, and the measurement of declination northwards or southwards from the equator; and the vernal equinox under the Square of Pegasus, the autumnal equinox, and the meaning of the word equinox ('equal night').