DATE Universal time (UT) of date. Time given is either 0h UT or the time of the day that is most favorable for observing the Comet. If you are looking at a different time of the day then some interpolation of the tabular values may be needed if they are rapidly changing. DEC,RA Declination and Right Ascension: Epoch 1950 or 2000. DELTA,R Comet-Earth and Comet-Sun distances in astronomical units (au). PHA Phase angle. Values between 50-130 degrees indicate a gas tail foreshortening of less than 25%. In the event of a close approach to the earth, this is also the maximum possible angular tail length of a very long straight gas tail pointing in the anti-solar direction. Values over 90 degrees indicate forward scattering could enhance the comet's brighteness. PLANE Angle the Comet-Earth line makes with the plane of the Comet's orbit and dust tail. An angle of zero means the dust tail is viewed edge on; 90 deg is face on. TAIL (Gas) tail length in degrees assuming actual length according to Andreas Kammerer's formula (originally from ICQ 16, pp. 144-148, Oct. 1994, updated by personal communication in Mar. 1996 and by an additional empirical correction in Jan. 2014). TPA Position Angle towards which the gas tail should point (assuming it points directly away from the sun). This can be used to estimate the PA of the line connecting the sun and comet to help find comets in bright twilight or daylight. It also gives an estimate of the best latitude on earth to see the comet. For an evening comet this would be approximately 90-TPA. For a morning comet it would be TPA-270. TLAU (Gas) tail length in AU according to the calculations in 'TAIL'. ALDF Comet minus Sun altitude when Comet is 3 Deg above horizon. Useful for bright comets embedded in twilight. For daylight comets (last column is 'D'), the instaneous altitude difference is shown. AZDF Comet minus Sun azimuth when Comet is 3 Deg above horizon For daylight comets (last column is 'D'), the instaneous azimuth difference is shown. RISE Rise Time (LST - Local Standard Time). TRAN Transit Time (LST) - often the best viewing time. SET Set Time (LST) Note that the RISE, TRAN, and SET times listed will change if you are at a different longitude within your time zone than the longitude (listed at the top) for which the ephemeris is calculated. Note that RISE, TRAN, and SET times are valid at the listed UT that was selected by the program for the daily report. These may have to be interpolated to the actual UT of the RISE, TRAN, and SET to obtain more accurate values, particularly if the comet is near to the sun or to the earth. A refraction of 34 arcminutes is assumed for the RISE and SET times. TWI Start or end time (LST) of Twilight if a limiting factor in Comet's visibility. Solar Depression angle of 16 degrees is used. 'R' or 'S' denotes morning or evening object, respectively. If the letter suffix is 'R' or 'S', the comet will be best seen in a twilight free sky. 'T' means the comet will instead be best viewed with twilight in progress at the stated time. MOON Moonrise or moonset time (LST) if moon interferes in Comet's visibility. Moon is considered bright when EMC < 1.8 X (EMS - 40) OR EMC < 6.0 X (EMS - 60). "R"/"S" denotes MOON Rise/Set, "T" denotes that due to the moon's interference, the best viewing will be at the "opposite" twilight from what one would expect if the moon were not a factor. ---------- BEST time for viewing Comet is TRANsit time ---------------- This is superseded by TWIlight time (if given). The first two are superseded by MOON time (if given). This is when the comet has the highest altitude (AL2) in a dark moonless sky. The BEST time is generally the same as the UT time. AL1 Altitude of Comet at best time for viewing taking twilight into account. If the letter suffix is 'R' or 'S', the comet will be best seen in a dark sky at the beginning/ending of twilight. 'T' means the comet will be best viewed in a brighter sky during twilight. AL2 Altitude of Comet at best time for viewing taking twilight and moonlight into account. Highest altitude comet can be seen in a sky free of both twilight and moonlight. If AL1 > 0 and AL2 = 0, the comet's visibility is strongly hampered by moonlight. AZ1 Azimuth of Comet at best time for viewing taking twilight into account. AZ2 Azimuth of Comet at best time for viewing taking twilight and moonlight into account (given when comet's visibility is strongly hampered by moonlight). EMS Elongation of the moon from the sun (corresponds to moon's phase). EMC Elongation of the moon from the Comet. MGLM Limiting magnitude of the sky in the vicinity of the comet. If the comet magnitude is brighter than this it should be visible by naked eye. VIS Effective magnitude of the comet, corrected for sky conditions such as extinction, twilight, moonlight, and daylight. If less than the stated naked eye limit (in output heading) the comet should be visible naked eye. You can instead use your own naked eye limit for dark sky cases without moonlight or twilight, otherwise the stated value should be used. If less than about 8.0 it should be visible in binoculars. Various characters accompany this parameter to signify observability: 'N' for nighttime comet viewable in a dark sky 'T' for twilight comet 'D' for daylight comet 'M' means it is hampered by moonlight (without any dark moon window at a favorable altitude) 'O' means best visible at moonrise or moonset (or near/into the opposite twilight due to moonlight) '-' means the comet is up only during daylight and is unobservably dim then ' ' a blank character means the comet is unobservable because it never risesEphemeris calculated by Steve Albers
Orbital Elements are generally from the CBAT page.