C/2020 H4 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	8 Jul 2020	16.2	1.285 AU	1.159 AU	23h55m	+77°41'	72.0°	48.8°	247°
Perihelion	28 Aug 2020	15.8	0.942 AU	1.608 AU	10h38m	+42°36'	33.2°	35.9°	5°
Today	22 May 2026	30.9	16.849 AU	16.784 AU	06h27m	-67°12'	92.0°	3.4°	145°

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)                : 0.9925900
    q (Perihelion distance)         : 0.9416870
    i (Inclination)                 : 84.28630
    Ω (Longitude of ascending node) : 307.39600
    ω (Argument of perihelion)      : 116.87060
    L (Longitude of perihelion)     : 296.27964
    B (Latitude of perihelion)      : 62.57292
    T (Time of perihelion passage)  : 2459090.03100
    P (Orbital period in years)     : 1432.63

    Epoch                           : 2026 May 21
    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
2026-05-21 00:00 UT   06 26 27.4   -67 14 49    16.776   16.843   92.0    3.4   144   30.9 
2026-05-22 00:00 UT   06 26 55.1   -67 13 02    16.782   16.848   92.0    3.4   144   30.9 
2026-05-22 05:38 UT   06 27 01.7   -67 12 37    16.784   16.849   92.0    3.4   145   30.9 
2026-05-23 00:00 UT   06 27 23.1   -67 11 18    16.788   16.854   91.9    3.4   145   30.9 
2026-05-24 00:00 UT   06 27 51.4   -67 09 36    16.795   16.859   91.9    3.4   146   30.9 
2026-05-25 00:00 UT   06 28 19.9   -67 07 57    16.801   16.865   91.9    3.4   147   30.9 
2026-05-26 00:00 UT   06 28 48.6   -67 06 21    16.807   16.870   91.8    3.4   148   30.9 
2026-05-27 00:00 UT   06 29 17.6   -67 04 48    16.813   16.876   91.8    3.4   149   30.9 
2026-05-28 00:00 UT   06 29 46.8   -67 03 17    16.819   16.881   91.8    3.4   150   30.9 
2026-05-29 00:00 UT   06 30 16.2   -67 01 50    16.825   16.887   91.7    3.4   150   31.0 
2026-05-30 00:00 UT   06 30 45.8   -67 00 25    16.832   16.892   91.7    3.4   151   31.0 
2026-05-31 00:00 UT   06 31 15.7   -66 59 02    16.838   16.898   91.7    3.4   152   31.0 
2026-06-01 00:00 UT   06 31 45.7   -66 57 43    16.844   16.904   91.6    3.4   153   31.0 

    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.