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	13 Oct 2026	31.2	17.640 AU	17.756 AU	07h25m	-70°43'	81.7°	3.2°	269°

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
2026-10-12 00:00 UT   07 25 32.6   -70 39 27    17.748   17.633   81.7    3.2   268   31.2 
2026-10-13 00:00 UT   07 25 30.9   -70 43 02    17.754   17.638   81.7    3.2   269   31.2 
2026-10-13 06:24 UT   07 25 30.4   -70 43 59    17.756   17.640   81.7    3.2   269   31.2 
2026-10-14 00:00 UT   07 25 28.6   -70 46 37    17.760   17.644   81.7    3.2   270   31.2 
2026-10-15 00:00 UT   07 25 25.5   -70 50 11    17.767   17.649   81.6    3.2   271   31.2 
2026-10-16 00:00 UT   07 25 21.7   -70 53 46    17.773   17.655   81.6    3.2   272   31.2 
2026-10-17 00:00 UT   07 25 17.2   -70 57 20    17.779   17.660   81.5    3.2   273   31.2 
2026-10-18 00:00 UT   07 25 12.0   -71 00 54    17.785   17.665   81.5    3.2   274   31.2 
2026-10-19 00:00 UT   07 25 06.1   -71 04 27    17.791   17.671   81.5    3.2   275   31.2 
2026-10-20 00:00 UT   07 24 59.4   -71 08 00    17.797   17.676   81.4    3.2   276   31.2 
2026-10-21 00:00 UT   07 24 52.0   -71 11 33    17.803   17.682   81.4    3.2   277   31.2 
2026-10-22 00:00 UT   07 24 43.8   -71 15 05    17.809   17.687   81.3    3.2   278   31.2 
2026-10-23 00:00 UT   07 24 34.9   -71 18 36    17.815   17.693   81.3    3.2   279   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.