Explanation of Comet Ephemeris Output

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

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 rises

Ephemeris calculated by Steve Albers

Orbital Elements are generally from the CBAT page.