C/2023 A1 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	1 Mar 2023	13.4	1.849 AU	1.187 AU	09h22m	+70°11'	115.9°	28.8°	156°
Perihelion	18 Mar 2023	13.6	1.837 AU	1.282 AU	07h37m	+52°22'	106.9°	31.2°	111°
Today	22 Oct 2025	24.7	9.085 AU	8.972 AU	03h28m	-74°02'	93.4°	6.3°	335°

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 10.4 + 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 A1 (Leonard) are:

    e (Eccentricity)                : 0.9917170
    q (Perihelion distance)         : 1.8368180
    i (Inclination)                 : 94.74480
    Ω (Longitude of ascending node) : 318.25340
    ω (Argument of perihelion)      : 159.27590
    L (Longitude of perihelion)     : 320.04596
    B (Latitude of perihelion)      : 20.64983
    T (Time of perihelion passage)  : 2460022.04490
    P (Orbital period in years)     : 3302.31

    Epoch                           : 2025 Oct 21
    Reference                       : MPEC 2024-GJ3

    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
2025-10-21 00:00 UT   03 31 23.2   -73 58 06     8.954    9.074   93.7    6.3   333   24.7 
2025-10-22 00:00 UT   03 29 37.4   -74 00 52     8.965    9.081   93.5    6.3   335   24.7 
2025-10-22 13:12 UT   03 28 38.8   -74 02 19     8.972    9.085   93.4    6.3   335   24.7 
2025-10-23 00:00 UT   03 27 50.7   -74 03 28     8.977    9.088   93.3    6.3   336   24.8 
2025-10-24 00:00 UT   03 26 02.9   -74 05 53     8.988    9.095   93.0    6.3   337   24.8 
2025-10-25 00:00 UT   03 24 14.3   -74 08 09     8.999    9.102   92.8    6.3   339   24.8 
2025-10-26 00:00 UT   03 22 24.9   -74 10 14     9.010    9.109   92.5    6.3   340   24.8 
2025-10-27 00:00 UT   03 20 34.7   -74 12 09     9.022    9.116   92.3    6.3   342   24.8 
2025-10-28 00:00 UT   03 18 43.9   -74 13 54     9.033    9.124   92.1    6.2   343   24.8 
2025-10-29 00:00 UT   03 16 52.5   -74 15 29     9.045    9.131   91.8    6.2   344   24.8 
2025-10-30 00:00 UT   03 15 00.5   -74 16 53     9.056    9.138   91.6    6.2   346   24.8 
2025-10-31 00:00 UT   03 13 08.2   -74 18 07     9.068    9.145   91.3    6.2   347   24.8 
2025-11-01 00:00 UT   03 11 15.5   -74 19 10     9.080    9.152   91.0    6.2   349   24.8 

    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.