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	29 Sep 2026	31.2	17.564 AU	17.667 AU	07h24m	-69°53'	82.4°	3.2°	256°

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
2026-09-28 00:00 UT   07 24 45.6   -69 49 39    17.659   17.557   82.5    3.2   255   31.2 
2026-09-29 00:00 UT   07 24 53.0   -69 53 09    17.665   17.562   82.4    3.2   256   31.2 
2026-09-29 05:17 UT   07 24 54.6   -69 53 56    17.667   17.564   82.4    3.2   256   31.2 
2026-09-30 00:00 UT   07 24 59.9   -69 56 40    17.672   17.568   82.4    3.2   256   31.2 
2026-10-01 00:00 UT   07 25 06.2   -70 00 12    17.678   17.573   82.3    3.2   257   31.2 
2026-10-02 00:00 UT   07 25 11.8   -70 03 44    17.685   17.579   82.3    3.2   258   31.2 
2026-10-03 00:00 UT   07 25 16.8   -70 07 17    17.691   17.584   82.2    3.2   259   31.2 
2026-10-04 00:00 UT   07 25 21.2   -70 10 50    17.698   17.589   82.1    3.2   260   31.2 
2026-10-05 00:00 UT   07 25 25.0   -70 14 24    17.704   17.595   82.1    3.2   261   31.2 
2026-10-06 00:00 UT   07 25 28.1   -70 17 58    17.710   17.600   82.0    3.2   262   31.2 
2026-10-07 00:00 UT   07 25 30.5   -70 21 32    17.717   17.606   82.0    3.2   263   31.2 
2026-10-08 00:00 UT   07 25 32.3   -70 25 07    17.723   17.611   81.9    3.2   264   31.2 
2026-10-09 00:00 UT   07 25 33.4   -70 28 42    17.729   17.617   81.9    3.2   265   31.2 

    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.