C/2023 X1 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	17 Oct 2023	14.2	0.954 AU	1.694 AU	11h34m	-18°08'	29.0°	30.4°	256°
Nearest approach	23 Dec 2023	15.0	1.466 AU	1.027 AU	13h22m	+45°08'	93.6°	42.1°	300°
Today	16 Sep 2026	28.5	10.515 AU	10.118 AU	21h15m	+61°17'	110.7°	5.1°	142°

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 13.3 + 5 log[∆] + 10.0 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 C/2023 X1 (Leonard) are:

    e (Eccentricity)                : 0.9938800
    q (Perihelion distance)         : 0.9535960
    i (Inclination)                 : 110.59560
    Ω (Longitude of ascending node) : 136.95840
    ω (Argument of perihelion)      : 321.50820
    L (Longitude of perihelion)     : 152.58620
    B (Latitude of perihelion)      : -35.63522
    T (Time of perihelion passage)  : 2460235.22650
    P (Orbital period in years)     : 1945.00

    Epoch                           : 2026 Sep 15
    Reference                       : MPC194187

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-09-15 00:00 UT   21 16 41.9   +61 24 51    10.110   10.504  110.5    5.1   144   28.5 
2026-09-16 00:00 UT   21 16 05.7   +61 20 13    10.115   10.511  110.6    5.1   143   28.5 
2026-09-16 11:38 UT   21 15 48.4   +61 17 57    10.118   10.515  110.7    5.1   142   28.5 
2026-09-17 00:00 UT   21 15 30.2   +61 15 31    10.120   10.518  110.7    5.1   142   28.5 
2026-09-18 00:00 UT   21 14 55.4   +61 10 44    10.126   10.525  110.8    5.1   141   28.5 
2026-09-19 00:00 UT   21 14 21.3   +61 05 52    10.131   10.532  110.9    5.1   139   28.5 
2026-09-20 00:00 UT   21 13 47.9   +61 00 56    10.137   10.539  111.0    5.1   138   28.5 
2026-09-21 00:00 UT   21 13 15.2   +60 55 56    10.142   10.547  111.1    5.1   137   28.5 
2026-09-22 00:00 UT   21 12 43.2   +60 50 51    10.148   10.554  111.2    5.1   136   28.5 
2026-09-23 00:00 UT   21 12 12.0   +60 45 43    10.154   10.561  111.3    5.1   135   28.5 
2026-09-24 00:00 UT   21 11 41.5   +60 40 30    10.161   10.568  111.3    5.1   133   28.5 
2026-09-25 00:00 UT   21 11 11.8   +60 35 14    10.167   10.575  111.4    5.1   132   28.5 
2026-09-26 00:00 UT   21 10 42.8   +60 29 54    10.173   10.582  111.4    5.1   131   28.5 

    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.