C/2023 A1 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	1 Mar 2023	13.4	1.850 AU	1.188 AU	09h22m	+70°08'	116.0°	28.8°	156°
Perihelion	18 Mar 2023	13.6	1.838 AU	1.282 AU	07h37m	+52°20'	107.0°	31.2°	111°
Today	20 Apr 2026	25.7	10.332 AU	10.560 AU	02h15m	-62°36'	74.2°	5.4°	174°

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)                : 0.9917540
    q (Perihelion distance)         : 1.8380030
    i (Inclination)                 : 94.74840
    Ω (Longitude of ascending node) : 318.24190
    ω (Argument of perihelion)      : 159.29570
    L (Longitude of perihelion)     : 320.03394
    B (Latitude of perihelion)      : 20.62999
    T (Time of perihelion passage)  : 2460021.98900
    P (Orbital period in years)     : 3327.78

    Epoch                           : 2026 Mar 16
    Reference                       : MPEC 2026-E44

    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
2026-04-19 00:00 UT   02 14 48.8   -62 38 11    10.557   10.323   73.8    5.4   173   25.7 
2026-04-20 00:00 UT   02 15 25.5   -62 37 02    10.559   10.330   74.1    5.4   174   25.7 
2026-04-20 08:30 UT   02 15 38.5   -62 36 38    10.560   10.332   74.2    5.4   174   25.7 
2026-04-21 00:00 UT   02 16 02.2   -62 35 57    10.561   10.337   74.4    5.4   174   25.7 
2026-04-22 00:00 UT   02 16 38.9   -62 34 58    10.563   10.343   74.7    5.4   175   25.7 
2026-04-23 00:00 UT   02 17 15.7   -62 34 04    10.565   10.350   75.0    5.4   176   25.7 
2026-04-24 00:00 UT   02 17 52.4   -62 33 14    10.567   10.357   75.3    5.4   177   25.7 
2026-04-25 00:00 UT   02 18 29.2   -62 32 29    10.568   10.364   75.6    5.4   178   25.7 
2026-04-26 00:00 UT   02 19 05.9   -62 31 50    10.570   10.370   75.9    5.4   178   25.7 
2026-04-27 00:00 UT   02 19 42.7   -62 31 15    10.571   10.377   76.2    5.4   179   25.7 
2026-04-28 00:00 UT   02 20 19.4   -62 30 45    10.573   10.384   76.5    5.4   180   25.7 
2026-04-29 00:00 UT   02 20 56.0   -62 30 20    10.574   10.391   76.8    5.4   181   25.7 
2026-04-30 00:00 UT   02 21 32.6   -62 30 00    10.575   10.397   77.1    5.4   182   25.7 

    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.