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	4 Dec 2025	30.5	15.514 AU	15.637 AU	07h05m	-74°01'	81.0°	3.6°	327°

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
2025-12-03 00:00 UT   07 06 53.7   -73 56 58    15.629   15.504   80.9    3.6   325   30.5 
2025-12-04 00:00 UT   07 06 05.3   -73 59 21    15.633   15.510   81.0    3.6   326   30.5 
2025-12-04 18:00 UT   07 05 28.5   -74 01 06    15.637   15.514   81.0    3.6   327   30.5 
2025-12-05 00:00 UT   07 05 16.2   -74 01 41    15.638   15.515   81.0    3.6   327   30.5 
2025-12-06 00:00 UT   07 04 26.4   -74 03 56    15.643   15.520   81.0    3.6   329   30.5 
2025-12-07 00:00 UT   07 03 35.8   -74 06 08    15.648   15.526   81.1    3.6   330   30.5 
2025-12-08 00:00 UT   07 02 44.7   -74 08 15    15.653   15.531   81.1    3.6   331   30.5 
2025-12-09 00:00 UT   07 01 52.8   -74 10 17    15.658   15.537   81.1    3.6   332   30.5 
2025-12-10 00:00 UT   07 01 00.3   -74 12 16    15.663   15.542   81.2    3.6   334   30.5 
2025-12-11 00:00 UT   07 00 07.2   -74 14 10    15.667   15.548   81.2    3.6   335   30.5 
2025-12-12 00:00 UT   06 59 13.5   -74 15 60    15.672   15.553   81.2    3.6   336   30.5 
2025-12-13 00:00 UT   06 58 19.3   -74 17 45    15.677   15.559   81.3    3.6   337   30.5 
2025-12-14 00:00 UT   06 57 24.5   -74 19 25    15.681   15.564   81.3    3.6   339   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.