C/2020 H7 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	25 May 2020	20.3	4.410 AU	3.742 AU	16h53m	+32°18'	125.7°	10.8°	192°
Perihelion	2 Jun 2020	20.3	4.409 AU	3.751 AU	16h38m	+32°59'	124.8°	10.9°	179°
Today	16 May 2026	28.8	15.258 AU	15.536 AU	08h25m	+06°56'	72.2°	3.6°	108°

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)                : 0.9993610
    q (Perihelion distance)         : 4.4094930
    i (Inclination)                 : 135.81780
    Ω (Longitude of ascending node) : 323.51620
    ω (Argument of perihelion)      : 82.61540
    L (Longitude of perihelion)     : 243.76050
    B (Latitude of perihelion)      : 43.72214
    T (Time of perihelion passage)  : 2459002.66510
    P (Orbital period in years)     : 573233.68

    Epoch                           : 2026 May 15
    Reference                       : MPEC 2026-FR0

    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
2026-05-15 00:00 UT   08 25 28.4   +06 56 21    15.506   15.250   73.5    3.6   108   28.8 
2026-05-16 00:00 UT   08 25 31.0   +06 56 27    15.527   15.256   72.6    3.6   108   28.8 
2026-05-16 10:35 UT   08 25 32.2   +06 56 29    15.536   15.258   72.2    3.6   108   28.8 
2026-05-17 00:00 UT   08 25 33.8   +06 56 31    15.548   15.261   71.7    3.6   108   28.8 
2026-05-18 00:00 UT   08 25 36.8   +06 56 35    15.569   15.266   70.7    3.6   108   28.8 
2026-05-19 00:00 UT   08 25 40.1   +06 56 37    15.590   15.271   69.8    3.6   108   28.8 
2026-05-20 00:00 UT   08 25 43.6   +06 56 38    15.611   15.277   68.9    3.5   109   28.8 
2026-05-21 00:00 UT   08 25 47.3   +06 56 38    15.632   15.282   68.0    3.5   109   28.8 
2026-05-22 00:00 UT   08 25 51.2   +06 56 37    15.653   15.287   67.0    3.5   109   28.8 
2026-05-23 00:00 UT   08 25 55.3   +06 56 34    15.674   15.292   66.1    3.5   109   28.8 
2026-05-24 00:00 UT   08 25 59.6   +06 56 31    15.694   15.298   65.2    3.4   110   28.8 
2026-05-25 00:00 UT   08 26 04.2   +06 56 26    15.715   15.303   64.3    3.4   110   28.8 
2026-05-26 00:00 UT   08 26 08.9   +06 56 20    15.735   15.308   63.4    3.4   110   28.8 

    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.