C/2020 H4 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	8 Jul 2020	16.2	1.279 AU	1.148 AU	23h53m	+77°45'	72.2°	49.2°	246°
Perihelion	29 Aug 2020	15.8	0.929 AU	1.603 AU	10h39m	+41°54'	32.6°	35.9°	4°
Today	13 Nov 2025	30.5	15.399 AU	15.528 AU	07h19m	-72°59'	80.7°	3.6°	303°

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. 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. (15.0 + 5 log[∆] + 8.0 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/2020 H4 (Leonard) are:

    e (Eccentricity)                : 0.9805970
    q (Perihelion distance)         : 0.9288190
    i (Inclination)                 : 84.49520
    Ω (Longitude of ascending node) : 307.42610
    ω (Argument of perihelion)      : 117.60040
    L (Longitude of perihelion)     : 297.02842
    B (Latitude of perihelion)      : 61.89835
    T (Time of perihelion passage)  : 2459090.56050
    P (Orbital period in years)     : 331.20

    Epoch                           : 2025 Nov 12
    Reference                       : MPEC 2020-L06

    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
2025-11-12 00:00 UT   07 20 35.4   -72 53 01    15.519   15.390   80.7    3.6   301   30.5 
2025-11-13 00:00 UT   07 20 05.4   -72 56 34    15.524   15.395   80.7    3.6   302   30.5 
2025-11-13 18:36 UT   07 19 41.5   -72 59 17    15.528   15.399   80.7    3.6   303   30.5 
2025-11-14 00:00 UT   07 19 34.4   -73 00 04    15.530   15.401   80.7    3.6   303   30.5 
2025-11-15 00:00 UT   07 19 02.5   -73 03 32    15.535   15.406   80.7    3.6   304   30.5 
2025-11-16 00:00 UT   07 18 29.7   -73 06 57    15.540   15.411   80.7    3.6   305   30.5 
2025-11-17 00:00 UT   07 17 55.9   -73 10 19    15.546   15.417   80.7    3.6   306   30.5 
2025-11-18 00:00 UT   07 17 21.2   -73 13 39    15.551   15.422   80.7    3.6   307   30.5 
2025-11-19 00:00 UT   07 16 45.5   -73 16 56    15.557   15.428   80.7    3.6   309   30.5 
2025-11-20 00:00 UT   07 16 08.9   -73 20 09    15.562   15.433   80.7    3.6   310   30.5 
2025-11-21 00:00 UT   07 15 31.4   -73 23 20    15.567   15.439   80.7    3.6   311   30.5 
2025-11-22 00:00 UT   07 14 53.0   -73 26 27    15.572   15.444   80.7    3.6   312   30.5 
2025-11-23 00:00 UT   07 14 13.7   -73 29 31    15.578   15.450   80.7    3.6   313   30.5 

    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.