C/2026 H2 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	17 Mar 2026	19.9	4.546 AU	4.421 AU	17h43m	+06°28'	90.9°	12.6°	271°
Nearest approach	21 May 2026	19.5	4.576 AU	3.699 AU	16h21m	+12°34'	146.4°	7.0°	194°
Today	4 Jun 2026	19.6	4.591 AU	3.742 AU	15h56m	+12°47'	142.7°	7.7°	161°

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. (10.1 + 5 log[∆] + 10.0 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/2026 H2 (Leonard) are:

    e (Eccentricity)                : 1.0013120
    q (Perihelion distance)         : 4.5460940
    i (Inclination)                 : 148.64990
    Ω (Longitude of ascending node) : 5.46000
    ω (Argument of perihelion)      : 111.52450
    L (Longitude of perihelion)     : 70.67110
    B (Latitude of perihelion)      : 28.94587
    T (Time of perihelion passage)  : 2461116.62670

    Epoch                           : 2026 Jun 03
    Reference                       : MPEC 2026-KB8

    Classification(s):              : Nearly isotropic; New (a > 10000 AU)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-06-03 00:00 UT   15 58 42.5   +12 48 16     3.735    4.589  143.4    7.6   163   19.6 
2026-06-04 00:00 UT   15 56 58.8   +12 47 58     3.741    4.590  142.8    7.7   161   19.6 
2026-06-04 03:26 UT   15 56 44.0   +12 47 54     3.742    4.591  142.7    7.7   161   19.6 
2026-06-05 00:00 UT   15 55 15.6   +12 47 29     3.747    4.592  142.2    7.8   159   19.6 
2026-06-06 00:00 UT   15 53 33.0   +12 46 48     3.754    4.593  141.6    7.9   157   19.6 
2026-06-07 00:00 UT   15 51 51.0   +12 45 56     3.761    4.594  140.9    8.0   155   19.6 
2026-06-08 00:00 UT   15 50 09.7   +12 44 53     3.769    4.595  140.2    8.1   153   19.6 
2026-06-09 00:00 UT   15 48 29.2   +12 43 39     3.777    4.596  139.5    8.2   151   19.6 
2026-06-10 00:00 UT   15 46 49.4   +12 42 14     3.785    4.597  138.8    8.4   150   19.6 
2026-06-11 00:00 UT   15 45 10.4   +12 40 39     3.793    4.599  138.0    8.5   148   19.6 
2026-06-12 00:00 UT   15 43 32.3   +12 38 53     3.803    4.600  137.2    8.6   147   19.6 
2026-06-13 00:00 UT   15 41 55.0   +12 36 56     3.812    4.601  136.4    8.8   145   19.6 
2026-06-14 00:00 UT   15 40 18.7   +12 34 49     3.822    4.602  135.6    8.9   144   19.6 

    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.