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	20 Jul 2026	31.1	17.179 AU	17.179 AU	06h58m	-66°54'	88.2°	3.4°	194°

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
2026-07-19 00:00 UT   06 57 40.2   -66 52 08    17.166   17.169   88.4    3.4   193   31.1 
2026-07-20 00:00 UT   06 58 12.3   -66 53 14    17.173   17.174   88.3    3.4   193   31.1 
2026-07-20 20:00 UT   06 58 39.0   -66 54 12    17.179   17.179   88.2    3.4   194   31.1 
2026-07-21 00:00 UT   06 58 44.3   -66 54 23    17.180   17.180   88.2    3.4   194   31.1 
2026-07-22 00:00 UT   06 59 16.2   -66 55 35    17.187   17.185   88.1    3.4   195   31.1 
2026-07-23 00:00 UT   06 59 48.0   -66 56 50    17.194   17.191   88.1    3.4   196   31.1 
2026-07-24 00:00 UT   07 00 19.6   -66 58 07    17.202   17.196   88.0    3.4   197   31.1 
2026-07-25 00:00 UT   07 00 51.1   -66 59 28    17.209   17.202   87.9    3.4   198   31.1 
2026-07-26 00:00 UT   07 01 22.5   -67 00 51    17.216   17.207   87.8    3.4   198   31.1 
2026-07-27 00:00 UT   07 01 53.7   -67 02 17    17.223   17.213   87.7    3.4   199   31.1 
2026-07-28 00:00 UT   07 02 24.7   -67 03 46    17.230   17.218   87.6    3.4   200   31.1 
2026-07-29 00:00 UT   07 02 55.6   -67 05 17    17.237   17.224   87.5    3.4   201   31.1 
2026-07-30 00:00 UT   07 03 26.3   -67 06 51    17.244   17.229   87.4    3.4   202   31.1 

    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.