C/2023 X1 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	17 Oct 2023	14.2	0.953 AU	1.694 AU	11h34m	-18°09'	29.0°	30.4°	256°
Nearest approach	23 Dec 2023	15.0	1.466 AU	1.027 AU	13h22m	+45°08'	93.5°	42.1°	300°
Today	12 Aug 2026	28.4	10.267 AU	10.010 AU	21h41m	+63°04'	101.8°	5.5°	184°

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)                : 0.9938790
    q (Perihelion distance)         : 0.9533890
    i (Inclination)                 : 110.59520
    Ω (Longitude of ascending node) : 136.95960
    ω (Argument of perihelion)      : 321.50450
    L (Longitude of perihelion)     : 152.58909
    B (Latitude of perihelion)      : -35.63867
    T (Time of perihelion passage)  : 2460235.24540
    P (Orbital period in years)     : 1943.89

    Epoch                           : 2026 Aug 11
    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
2026-08-11 00:00 UT   21 42 57.5   +63 05 37    10.009   10.257  101.4    5.6   185   28.4 
2026-08-12 00:00 UT   21 42 08.1   +63 04 35    10.010   10.264  101.7    5.5   184   28.4 
2026-08-12 07:50 UT   21 41 51.9   +63 04 13    10.010   10.267  101.8    5.5   184   28.4 
2026-08-13 00:00 UT   21 41 18.6   +63 03 26    10.011   10.271  102.1    5.5   183   28.4 
2026-08-14 00:00 UT   21 40 29.2   +63 02 10    10.013   10.278  102.4    5.5   182   28.4 
2026-08-15 00:00 UT   21 39 39.9   +63 00 48    10.014   10.286  102.8    5.5   181   28.4 
2026-08-16 00:00 UT   21 38 50.6   +62 59 18    10.015   10.293  103.1    5.5   180   28.4 
2026-08-17 00:00 UT   21 38 01.5   +62 57 42    10.017   10.300  103.4    5.5   178   28.4 
2026-08-18 00:00 UT   21 37 12.5   +62 55 59    10.019   10.307  103.8    5.5   177   28.4 
2026-08-19 00:00 UT   21 36 23.6   +62 54 09    10.020   10.314  104.1    5.5   176   28.4 
2026-08-20 00:00 UT   21 35 35.0   +62 52 12    10.022   10.321  104.4    5.4   175   28.4 
2026-08-21 00:00 UT   21 34 46.5   +62 50 09    10.024   10.328  104.7    5.4   174   28.4 
2026-08-22 00:00 UT   21 33 58.3   +62 47 59    10.026   10.335  105.0    5.4   173   28.4 

    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.