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Frank,
Because of the axial tilt of the Earth, the time difference between sunrise and sunset in Sydney can vary anywhere from about 10 hours in winter to 14 hours in summer. The Sun rises and sets everyday and is highest in the sky at midday.
The Moon follows roughly the same path as the Sun across the sky but moves in the opposite direction at about 13 degrees per day relative to the background stars. This means the Moon rises and sets an average of about 52 minutes later each day (13/360x24hours). So from moonrise to moonrise is roughly 25 hours and from moonset to moonset is roughly 25 hours. As there are more than 25 days each month, this means there has to be at least one day each month when the Moon does not rise on that day. For example, on Aug 12th moonrise is 11:24pm but next moonrise is Aug 14th at 12:29am about 25 hours later. The same applies to moonset. On Aug 26th moonset is 11:59pm but next moonset is Aug 28th at 12:58am about 25 hours later. Interestingly, the time difference between moonrise and moonset can vary anywhere from about 10 hours to 15 hours.
Regards, Rob
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