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 Mar. 1996).
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.
AZDF Comet minus Sun azimuth when Comet is 3 Deg above horizon
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. "S" or "R"
denotes evening or morning object, respectively.
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 occurs 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.
Highest altitude comet can be seen in a twilight free sky.
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.
Ephemeris calculated by Steve Albers
Orbital Elements are generally from the CBAT page.