C/2020 H7 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	26 May 2020	20.3	4.420 AU	3.750 AU	16h53m	+32°09'	125.8°	10.7°	192°
Perihelion	2 Jun 2020	20.3	4.420 AU	3.762 AU	16h37m	+32°52'	124.8°	10.9°	178°
Today	29 Oct 2025	28.3	14.177 AU	14.319 AU	09h04m	+06°04'	79.8°	4.0°	285°

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. (11.0 + 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/2020 H7 (Lemmon) are:

    e (Eccentricity)                : 0.9968540
    q (Perihelion distance)         : 4.4195450
    i (Inclination)                 : 135.92350
    Ω (Longitude of ascending node) : 323.51940
    ω (Argument of perihelion)      : 82.67800
    L (Longitude of perihelion)     : 243.65995
    B (Latitude of perihelion)      : 43.62582
    T (Time of perihelion passage)  : 2459003.45090
    P (Orbital period in years)     : 52653.62

    Epoch                           : 
    Reference                       : MPEC 2020-KB7

    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
2025-10-28 00:00 UT   09 04 18.9   +06 06 29    14.341   14.167   78.0    3.9   285   28.3 
2025-10-29 00:00 UT   09 04 17.7   +06 05 12    14.329   14.173   79.0    3.9   285   28.3 
2025-10-29 20:45 UT   09 04 16.3   +06 04 06    14.319   14.177   79.8    4.0   285   28.3 
2025-10-30 00:00 UT   09 04 16.1   +06 03 56    14.317   14.178   79.9    4.0   285   28.3 
2025-10-31 00:00 UT   09 04 14.3   +06 02 41    14.306   14.183   80.9    4.0   285   28.3 
2025-11-01 00:00 UT   09 04 12.1   +06 01 26    14.294   14.189   81.9    4.0   285   28.3 
2025-11-02 00:00 UT   09 04 09.7   +06 00 13    14.282   14.194   82.9    4.0   286   28.3 
2025-11-03 00:00 UT   09 04 07.1   +05 59 01    14.270   14.199   83.9    4.0   286   28.3 
2025-11-04 00:00 UT   09 04 04.1   +05 57 50    14.258   14.205   84.9    4.0   286   28.3 
2025-11-05 00:00 UT   09 04 00.9   +05 56 40    14.247   14.210   85.9    4.0   286   28.3 
2025-11-06 00:00 UT   09 03 57.3   +05 55 31    14.235   14.215   86.9    4.0   286   28.3 
2025-11-07 00:00 UT   09 03 53.5   +05 54 23    14.223   14.221   87.9    4.0   287   28.3 
2025-11-08 00:00 UT   09 03 49.4   +05 53 17    14.211   14.226   88.9    4.0   287   28.3 

    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.