C/2020 W5 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	1 Dec 2020	22.3	3.372 AU	2.519 AU	04h55m	+56°44'	144.7°	9.7°	191°
Nearest approach	1 Dec 2020	22.3	3.372 AU	2.519 AU	04h53m	+56°57'	144.8°	9.7°	188°
Today	9 Jan 2026	32.3	14.088 AU	14.781 AU	17h15m	+09°19'	43.8°	2.8°	316°

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[∆] + 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 W5 (Lemmon) are:

    e (Eccentricity)                : 1.0023490
    q (Perihelion distance)         : 3.3721600
    i (Inclination)                 : 88.61020
    Ω (Longitude of ascending node) : 75.47100
    ω (Argument of perihelion)      : 24.62830
    L (Longitude of perihelion)     : 76.10804
    B (Latitude of perihelion)      : 24.62057
    T (Time of perihelion passage)  : 2459184.59560

    Epoch                           : 2025 Nov 12
    Reference                       : MPEC 2021-BE3

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-01-08 00:00 UT   17 15 27.0   +09 19 14    14.783   14.082   43.1    2.7   318   32.3 
2026-01-09 00:00 UT   17 15 41.1   +09 19 20    14.781   14.088   43.7    2.8   316   32.3 
2026-01-09 03:16 UT   17 15 43.0   +09 19 21    14.781   14.088   43.8    2.8   316   32.3 
2026-01-10 00:00 UT   17 15 55.1   +09 19 28    14.779   14.093   44.4    2.8   315   32.3 
2026-01-11 00:00 UT   17 16 08.9   +09 19 38    14.777   14.099   45.0    2.8   314   32.3 
2026-01-12 00:00 UT   17 16 22.6   +09 19 51    14.774   14.105   45.6    2.9   313   32.3 
2026-01-13 00:00 UT   17 16 36.1   +09 20 05    14.772   14.110   46.3    2.9   312   32.3 
2026-01-14 00:00 UT   17 16 49.5   +09 20 21    14.769   14.116   46.9    2.9   311   32.3 
2026-01-15 00:00 UT   17 17 02.7   +09 20 40    14.766   14.122   47.6    2.9   310   32.3 
2026-01-16 00:00 UT   17 17 15.8   +09 21 00    14.763   14.127   48.2    3.0   309   32.3 
2026-01-17 00:00 UT   17 17 28.7   +09 21 23    14.759   14.133   48.9    3.0   308   32.3 
2026-01-18 00:00 UT   17 17 41.4   +09 21 47    14.756   14.139   49.6    3.0   308   32.3 
2026-01-19 00:00 UT   17 17 54.0   +09 22 14    14.752   14.144   50.3    3.1   307   32.4 

    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.