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Triple Horizontal Sundial with a Nocturnal
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This 520mm diameter stainless steel sundial consists of 3 sundials and a nocturnal for
telling time at night from the stars. Of course our beloved Southern Cross is one of those stars. The outer dial reads local solar time in the normal way. The oval dial to the north reads longitude corrected local solar time. It contains circles indicating solar altitude and arcs which indicate solar declination, the changes in the Zodiac and birthdays of family members and is thus a solar calendar, the dent in the
the shadow from the nodus point running along these lines on the appropriate day.
The stereographic grid reads directly to South African Standard Time and tells solar
altitude, solar declination and solar azimuth for every sunlit moment plus solstices,
equinoxes, approximate time of sunrise and sunset, day, date, month, season, plus solar right ascension.
The Equation of Time is expressed as an integer around a calendar for each day of the year.
The declination and right ascension for all stars on the nocturnal are given and when a known star is on the meridian the time at night is read against the date. Inversely, if time and date are known the
navigational star on the meridian is named. All stars listed are of magnitude 2.5 and less and all are clearly visible from South Africa at various times of year.
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