C/2021 G1 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	20 Jul 2021	22.4	3.429 AU	4.079 AU	10h54m	+47°25'	44.5°	12.0°	69°
Nearest approach	11 Jan 2022	22.1	3.774 AU	2.935 AU	08h55m	+54°19'	143.8°	8.9°	214°
Today	16 Sep 2025	30.0	11.695 AU	11.356 AU	04h29m	-11°06'	107.3°	4.7°	271°

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 G1 (Leonard) are:

            e (Eccentricity)                : 0.9516630
            q (Perihelion distance)         : 3.4287940
            i (Inclination)                 : 131.54640
            Ω (Longitude of ascending node) : 270.69710
            ω (Argument of perihelion)      : 107.44030
            L (Longitude of perihelion)     : 335.35136
            B (Latitude of perihelion)      : 45.56244
            T (Time of perihelion passage)  : 2459415.66960
            P (Orbital period in years)     : 597.44

            Epoch                           : 2025 Sep 16
            Reference                       : MPEC 2021-J72

            Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)
        

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 light curve is based on the absolute magnitude and slope parameter as calculated from an MPEC, or the latest values provided by the minor planet center. (14.00 + 5 log[∆] + 10.00 log[r]).

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
2025-09-16 00:00 UT   04 29 20.2   -11 02 54    11.364   11.689  106.5    4.7   270   30.0 
2025-09-16 23:09 UT   04 29 11.6   -11 06 34    11.356   11.695  107.3    4.7   271   30.0 
2025-09-17 00:00 UT   04 29 11.3   -11 06 42    11.356   11.695  107.3    4.7   271   30.0 
2025-09-18 00:00 UT   04 29 01.9   -11 10 30    11.348   11.701  108.2    4.7   272   30.0 
2025-09-19 00:00 UT   04 28 52.2   -11 14 18    11.340   11.706  109.0    4.7   272   30.0 
2025-09-20 00:00 UT   04 28 42.2   -11 18 07    11.332   11.712  109.9    4.6   273   30.0 
2025-09-21 00:00 UT   04 28 31.8   -11 21 55    11.325   11.718  110.7    4.6   273   30.0 
2025-09-22 00:00 UT   04 28 21.0   -11 25 44    11.317   11.723  111.5    4.6   274   30.0 
2025-09-23 00:00 UT   04 28 09.8   -11 29 32    11.310   11.729  112.4    4.5   275   30.0 
2025-09-24 00:00 UT   04 27 58.4   -11 33 20    11.303   11.735  113.2    4.5   275   30.0 
2025-09-25 00:00 UT   04 27 46.5   -11 37 08    11.296   11.740  114.0    4.5   276   30.0 
2025-09-26 00:00 UT   04 27 34.3   -11 40 56    11.289   11.746  114.9    4.4   277   30.0 

    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.