103P/Hartley
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	26 Sep 2023	9.5	1.090 AU	0.393 AU	06h01m	+34°30'	92.0°	66.9°	270°
Perihelion	12 Oct 2023	9.4	1.067 AU	0.415 AU	07h27m	+21°06'	87.9°	69.2°	278°
Today	24 Jul 2026	27.9	5.803 AU	5.835 AU	13h30m	-10°42'	83.2°	10.0°	112°

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. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 10.8 + 5 log[∆] + 17.3 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 103P/Hartley are:

    e (Eccentricity)                : 0.6931040
    q (Perihelion distance)         : 1.0669380
    i (Inclination)                 : 13.59980
    Ω (Longitude of ascending node) : 219.76460
    ω (Argument of perihelion)      : 181.33440
    L (Longitude of perihelion)     : 221.06160
    B (Latitude of perihelion)      : -0.31374
    T (Time of perihelion passage)  : 2460229.59440
    P (Orbital period in years)     : 6.48

    Epoch                           : 2026 Jul 24
    Reference                       : MPC191602

    Classification(s):              : Ecliptic; Jupiter family
    Tisserand (Jupiter)             : 2.642

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-07-23 00:00 UT   13 29 36.2   -10 41 31     5.804    5.801   84.9   10.0   112   27.9 
2026-07-24 00:00 UT   13 29 50.1   -10 42 04     5.821    5.802   84.0   10.0   112   27.9 
2026-07-24 20:30 UT   13 30 02.5   -10 42 34     5.835    5.803   83.2   10.0   112   27.9 
2026-07-25 00:00 UT   13 30 04.6   -10 42 40     5.838    5.803   83.1   10.0   112   27.9 
2026-07-26 00:00 UT   13 30 19.7   -10 43 20     5.855    5.804   82.2   10.0   112   27.9 
2026-07-27 00:00 UT   13 30 35.3   -10 44 03     5.872    5.805   81.3   10.0   112   27.9 
2026-07-28 00:00 UT   13 30 51.4   -10 44 49     5.889    5.806   80.4    9.9   112   27.9 
2026-07-29 00:00 UT   13 31 08.1   -10 45 39     5.906    5.807   79.5    9.9   112   27.9 
2026-07-30 00:00 UT   13 31 25.3   -10 46 31     5.923    5.808   78.6    9.9   112   27.9 
2026-07-31 00:00 UT   13 31 43.0   -10 47 28     5.940    5.809   77.7    9.8   112   27.9 
2026-08-01 00:00 UT   13 32 01.1   -10 48 27     5.956    5.810   76.9    9.8   112   27.9 
2026-08-02 00:00 UT   13 32 19.8   -10 49 29     5.973    5.811   76.0    9.8   112   27.9 
2026-08-03 00:00 UT   13 32 39.0   -10 50 35     5.990    5.812   75.1    9.7   112   27.9 

    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.