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	4.410 AU	3.751 AU	16h38m	+32°59'	124.8°	10.9°	179°
Today	18 Oct 2026	29.1	16.064 AU	16.339 AU	08h46m	+04°17'	72.3°	3.4°	281°

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)                : 0.9993320
    q (Perihelion distance)         : 4.4095720
    i (Inclination)                 : 135.81720
    Ω (Longitude of ascending node) : 323.51600
    ω (Argument of perihelion)      : 82.61450
    L (Longitude of perihelion)     : 243.76164
    B (Latitude of perihelion)      : 43.72262
    T (Time of perihelion passage)  : 2459002.60950
    P (Orbital period in years)     : 536327.37

    Epoch                           : 2026 May 29
    Reference                       : MPC194167

    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
2026-10-17 00:00 UT   08 46 07.3   +04 19 31    16.353   16.058   71.0    3.4   281   29.1 
2026-10-18 00:00 UT   08 46 08.1   +04 18 09    16.342   16.063   72.0    3.4   281   29.1 
2026-10-18 07:56 UT   08 46 08.3   +04 17 43    16.339   16.064   72.3    3.4   281   29.1 
2026-10-19 00:00 UT   08 46 08.7   +04 16 49    16.331   16.068   72.9    3.4   282   29.1 
2026-10-20 00:00 UT   08 46 09.1   +04 15 28    16.320   16.073   73.9    3.4   282   29.1 
2026-10-21 00:00 UT   08 46 09.3   +04 14 09    16.309   16.078   74.9    3.4   282   29.1 
2026-10-22 00:00 UT   08 46 09.2   +04 12 50    16.298   16.083   75.8    3.4   282   29.1 
2026-10-23 00:00 UT   08 46 08.9   +04 11 31    16.286   16.089   76.8    3.5   283   29.1 
2026-10-24 00:00 UT   08 46 08.3   +04 10 14    16.275   16.094   77.8    3.5   283   29.1 
2026-10-25 00:00 UT   08 46 07.5   +04 08 57    16.263   16.099   78.7    3.5   283   29.1 
2026-10-26 00:00 UT   08 46 06.5   +04 07 40    16.252   16.104   79.7    3.5   283   29.1 
2026-10-27 00:00 UT   08 46 05.2   +04 06 25    16.240   16.109   80.7    3.5   283   29.1 
2026-10-28 00:00 UT   08 46 03.7   +04 05 10    16.228   16.114   81.6    3.5   284   29.1 

    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.