C/2023 X1 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	17 Oct 2023	14.2	0.954 AU	1.695 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°	42.0°	300°
Today	30 Sep 2026	28.6	10.614 AU	10.205 AU	21h08m	+60°04'	111.5°	5.0°	125°

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)         : 0.9536790
    i (Inclination)                 : 110.59580
    Ω (Longitude of ascending node) : 136.95760
    ω (Argument of perihelion)      : 321.50960
    L (Longitude of perihelion)     : 152.58479
    B (Latitude of perihelion)      : -35.63391
    T (Time of perihelion passage)  : 2460235.21850
    P (Orbital period in years)     : 1945.25

    Epoch                           : 2026 Sep 29
    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
2026-09-29 00:00 UT   21 09 20.5   +60 13 33    10.193   10.603  111.5    5.0   127   28.5 
2026-09-30 00:00 UT   21 08 54.6   +60 07 59    10.200   10.610  111.5    5.0   126   28.6 
2026-09-30 16:11 UT   21 08 37.5   +60 04 12    10.205   10.614  111.5    5.0   125   28.6 
2026-10-01 00:00 UT   21 08 29.4   +60 02 22    10.208   10.617  111.5    5.0   125   28.6 
2026-10-02 00:00 UT   21 08 05.1   +59 56 43    10.215   10.623  111.5    5.0   124   28.6 
2026-10-03 00:00 UT   21 07 41.5   +59 50 60    10.222   10.630  111.5    5.0   123   28.6 
2026-10-04 00:00 UT   21 07 18.7   +59 45 15    10.230   10.637  111.5    5.0   121   28.6 
2026-10-05 00:00 UT   21 06 56.7   +59 39 27    10.238   10.644  111.4    5.0   120   28.6 
2026-10-06 00:00 UT   21 06 35.5   +59 33 36    10.245   10.651  111.4    5.0   119   28.6 
2026-10-07 00:00 UT   21 06 15.1   +59 27 43    10.253   10.658  111.3    5.0   118   28.6 
2026-10-08 00:00 UT   21 05 55.4   +59 21 48    10.261   10.665  111.3    5.0   117   28.6 
2026-10-09 00:00 UT   21 05 36.6   +59 15 50    10.270   10.672  111.2    5.0   116   28.6 
2026-10-10 00:00 UT   21 05 18.5   +59 09 51    10.278   10.679  111.1    5.0   114   28.6 

    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.