C/2021 A1 (Leonard) - DISINTEGRATED
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	13 Dec 2021	2.9	0.774 AU	0.233 AU	17h12m	-00°52'	22.3°	151.1°	355°
Perihelion	3 Jan 2022	5.9	0.615 AU	0.924 AU	21h40m	-35°25'	37.5°	76.5°	98°
Disintegration	1 Mar 2022	11.0	1.280 AU	1.992 AU	21h24m	-34°51'	32.9°	24.9°	220°
Today	2 Oct 2025	-	12.979 AU	13.592 AU	15h57m	-06°19'	50.5°	3.4°	90°

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.)

The orbital elements of C/2021 A1 (Leonard) are:

            e (Eccentricity)                : 1.0002620
            q (Perihelion distance)         : 0.6150090
            i (Inclination)                 : 132.74900
            Ω (Longitude of ascending node) : 255.90880
            ω (Argument of perihelion)      : 225.12980
            L (Longitude of perihelion)     : 221.61988
            B (Latitude of perihelion)      : -31.36095
            T (Time of perihelion passage)  : 2459583.44070

            Epoch                           : 2025 Oct 01
            Reference                       : MPEC 2025-A40

            Classification(s):              : Nearly isotropic; New (a > 10000 AU)
        

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. The gray curve is based on the absolute magnitude and slope parameter as calculated from the original MPEC, or the latest values provided by the MPC (8.50 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 8.37 + 5 log[∆] + 11.01 log[r]). The additional green curve shows the effect of forward scattering, occurring when the comet is between the earth and the sun, for a gas-to-dust light ratio δ90 of 0.10. (See Marcus 2007)

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-10-02 00:00 UT   15 57 32.3   -06 18 48    13.575   12.973   51.3    3.5    91   26.3 
2025-10-02 21:22 UT   15 57 41.5   -06 19 45    13.592   12.979   50.5    3.4    90   26.3 
2025-10-03 00:00 UT   15 57 42.6   -06 19 51    13.594   12.980   50.4    3.4    90   26.3 
2025-10-04 00:00 UT   15 57 53.1   -06 20 54    13.613   12.986   49.5    3.4    90   26.3 
2025-10-05 00:00 UT   15 58 03.8   -06 21 57    13.632   12.993   48.6    3.3    89   26.3 
2025-10-06 00:00 UT   15 58 14.7   -06 22 60    13.651   12.999   47.7    3.3    89   26.3 
2025-10-07 00:00 UT   15 58 25.7   -06 24 02    13.669   13.006   46.8    3.2    89   26.3 
2025-10-08 00:00 UT   15 58 37.0   -06 25 04    13.687   13.013   45.9    3.2    88   26.3 
2025-10-09 00:00 UT   15 58 48.4   -06 26 06    13.705   13.019   45.0    3.1    88   26.3 
2025-10-10 00:00 UT   15 59 00.1   -06 27 07    13.723   13.026   44.2    3.1    87   26.3 
2025-10-11 00:00 UT   15 59 11.9   -06 28 09    13.741   13.032   43.3    3.0    87   26.3 
2025-10-12 00:00 UT   15 59 23.8   -06 29 09    13.758   13.039   42.4    3.0    86   26.3 

    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.