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°37'	33.2°	35.9°	5°
Today	1 Jun 2026	31.0	16.905 AU	16.846 AU	06h31m	-66°57'	91.6°	3.4°	153°

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)                : 0.9925890
    q (Perihelion distance)         : 0.9418040
    i (Inclination)                 : 84.28630
    Ω (Longitude of ascending node) : 307.39580
    ω (Argument of perihelion)      : 116.87240
    L (Longitude of perihelion)     : 296.28029
    B (Latitude of perihelion)      : 62.57116
    T (Time of perihelion passage)  : 2459090.01580
    P (Orbital period in years)     : 1432.60

    Epoch                           : 2026 May 29
    Reference                       : MPC194166

    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
2026-05-31 00:00 UT   06 31 15.7   -66 59 03    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 
2026-06-01 07:51 UT   06 31 55.6   -66 57 18    16.846   16.905   91.6    3.4   153   31.0 
2026-06-02 00:00 UT   06 32 15.9   -66 56 27    16.850   16.909   91.6    3.4   154   31.0 
2026-06-03 00:00 UT   06 32 46.4   -66 55 13    16.857   16.915   91.5    3.4   155   31.0 
2026-06-04 00:00 UT   06 33 17.0   -66 54 02    16.863   16.920   91.5    3.4   155   31.0 
2026-06-05 00:00 UT   06 33 47.8   -66 52 54    16.869   16.926   91.4    3.4   156   31.0 
2026-06-06 00:00 UT   06 34 18.8   -66 51 49    16.876   16.931   91.4    3.4   157   31.0 
2026-06-07 00:00 UT   06 34 49.9   -66 50 47    16.882   16.937   91.3    3.4   158   31.0 
2026-06-08 00:00 UT   06 35 21.2   -66 49 47    16.889   16.942   91.3    3.4   159   31.0 
2026-06-09 00:00 UT   06 35 52.6   -66 48 51    16.895   16.948   91.2    3.4   160   31.0 
2026-06-10 00:00 UT   06 36 24.2   -66 47 57    16.902   16.953   91.2    3.4   160   31.0 
2026-06-11 00:00 UT   06 36 55.9   -66 47 07    16.908   16.959   91.1    3.4   161   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.