123P/West-Hartley
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Today	22 Nov 2025	17.7	3.059 AU	2.076 AU	03h55m	+26°48'	173.3°	2.2°	188°
Perihelion	22 Sep 2026	14.8	2.158 AU	3.057 AU	11h00m	+17°38'	21.8°	10.0°	320°
Nearest approach	17 Apr 2027	15.7	2.655 AU	1.678 AU	14h47m	-12°08'	163.3°	6.2°	274°

The interactive orbit chart above shows the comet's path through the solar system and its position at the given date. Green and blue lines are shown perpendicular to the ecliptic plane: Green if the path is above the ecliptic plane, blue if it is below. (Left-click and drag to rotate the view; Right-click and drag to move the view; Use scroll wheel to zoom in our out.)

Light curve

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations from COBS. The light curve is based on the absolute magnitude and slope parameter as calculated from an MPEC, or the latest values provided by the minor planet center. (4.0 + 5 log[∆] + 25.0 log[r]). An additional green curve is displayed when an increase in apparent brightness is expected due to forward scattering of sunlight, which occurs when a dust-rich comet is located between the Earth and the Sun. (See Marcus 2007)

Charts

The all-sky chart below shows the path of the comet over the same period as the light curve. The comet's current position is marked yellow.

The following chart shows the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Orbital elements

The orbital elements of 123P/West-Hartley are:

    e (Eccentricity)                : 0.4446280
    q (Perihelion distance)         : 2.1580280
    i (Inclination)                 : 15.28670
    Ω (Longitude of ascending node) : 45.88010
    ω (Argument of perihelion)      : 103.92960
    L (Longitude of perihelion)     : -29.70032
    B (Latitude of perihelion)      : 14.82667
    T (Time of perihelion passage)  : 2461305.59660
    P (Orbital period in years)     : 7.66

    Epoch                           : 2025 Nov 21
    Reference                       : MPEC 2025-W75

    Classification(s):              : Ecliptic; Jupiter family
    Tisserand (Jupiter)             : 2.832

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-11-21 00:00 UT   03 57 32.6   +26 45 48     2.084    3.066  172.5    2.4   203   17.8 
2025-11-22 00:00 UT   03 56 32.5   +26 47 38     2.079    3.062  173.1    2.2   194   17.7 
2025-11-22 14:40 UT   03 55 55.6   +26 48 42     2.076    3.059  173.3    2.2   188   17.7 
2025-11-23 00:00 UT   03 55 32.1   +26 49 23     2.074    3.058  173.4    2.1   184   17.7 
2025-11-24 00:00 UT   03 54 31.4   +26 51 03     2.070    3.053  173.6    2.1   173   17.7 
2025-11-25 00:00 UT   03 53 30.4   +26 52 40     2.066    3.049  173.5    2.1   162   17.7 
2025-11-26 00:00 UT   03 52 29.3   +26 54 11     2.062    3.045  173.2    2.2   151   17.7 
2025-11-27 00:00 UT   03 51 28.0   +26 55 39     2.059    3.040  172.7    2.4   142   17.6 
2025-11-28 00:00 UT   03 50 26.8   +26 57 02     2.056    3.036  172.0    2.6   134   17.6 
2025-11-29 00:00 UT   03 49 25.5   +26 58 20     2.053    3.032  171.2    2.8   128   17.6 
2025-11-30 00:00 UT   03 48 24.4   +26 59 35     2.051    3.027  170.3    3.1   122   17.6 
2025-12-01 00:00 UT   03 47 23.4   +27 00 46     2.048    3.023  169.4    3.4   118   17.6 
2025-12-02 00:00 UT   03 46 22.6   +27 01 52     2.046    3.019  168.4    3.8   114   17.6 

    Terminology:
            
    delta:  distance between comet and earth in AU
    radius: distance between comet and sun in AU
    magn:   magnitude (brightness) estimate    
    ra:     right ascension in hours (24h = 360deg)
    dec:    declination in degrees
    elong:  elongation in degrees (angle sun-earth-comet)    
    phase:  phase angle in degrees (angle sun-comet-earth)        
    AU:     Astronomical Unit (mean distance between earth and sun: 149597870.7 km      
    

Orbital elements usually provided by the MPC (Minor Planet Center).
Observations contributed by observers worldwide, via COBS (Comet Observation Database) or the MPC (Minor Planet Center)
Calculations by a modified version of AAPlus, a C# implementation of the AA+ project by PJ Naughter from the algorithms presented in the book "Astronomical Algorithms" by Jean Meeus.
NGC2000 dso catalog and star labels from VizieR as provided by the Strasbourg astronomical Data Center.
Tycho2 catalog from the ESO archive.