The following notes describe the format of the comet ephemerides. Line No: 1 Name of comet 2,3 Orbital elements 4 Magnitude formula 5,6 Station details. Usually UK (53 N, 0W). 7 Conditions for the comet to be observable. Usually they are that the sun is 13 degrees below the horizon (ie sky is dark) and the comet a value above the horizon that depends on its predicted brightness. 8 Month, year. Strictly ephemeris time is used, this is currently some 55 seconds ahead of UT. 9,10 Column headings: a) Double date. The first date is the date before midnight, the second one after midnight. b) Right ascension in hours and minutes Declination in degrees and minutes (For equinox 1950 which is the epoch used in the AAVSO star atlas) Right ascension in hours and minutes Declination in degrees and minutes (For equinox 2000 which is close to the position indicated by setting circles) c) Magnitude of comet. This is an indication only and may be several magnitudes out. A comet appears much fainter in a large telescope than in binoculars. d) Distance from the earth in astronomical units. e) Distance from the sun in astronomical units. f) Time of transit, ie when the comet is highest in the sky. g) Period of observability subject to the constraints in line 7. The comet may be visible outside this period. The times will approximate to local time for other longitudes if the station is near the Greenwich meridian. h) Elongation from the sun in degrees. i) Elongation from the moon in degrees (approximate) j) Phase of moon (approximate) k) A prediction for the apparent length of tail that the comet will have (in minutes of arc) using a formula for tail length developed by Andreas Kamerer. l) Position angle of the tail (assuming it lies along the radius vector). North=0, East=90, South=180, West=270 m) Rate of motion in RA (degrees/day x 25) n) Rate of motion in dec (degrees/day x 25) Columns i-n may be omitted in some ephemerides.