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 Dec 2025	32.3	13.913 AU	14.734 AU	17h07m	+09°33'	32.4°	2.2°	2°

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
2025-12-08 00:00 UT   17 07 25.9   +09 34 22    14.728   13.906   32.3    2.2     4   32.3 
2025-12-09 00:00 UT   17 07 42.1   +09 33 19    14.733   13.911   32.4    2.2     2   32.3 
2025-12-09 04:45 UT   17 07 45.3   +09 33 07    14.734   13.913   32.4    2.2     2   32.3 
2025-12-10 00:00 UT   17 07 58.3   +09 32 18    14.738   13.917   32.4    2.2     0   32.3 
2025-12-11 00:00 UT   17 08 14.5   +09 31 19    14.743   13.923   32.5    2.2   359   32.3 
2025-12-12 00:00 UT   17 08 30.7   +09 30 23    14.747   13.929   32.6    2.2   357   32.3 
2025-12-13 00:00 UT   17 08 46.9   +09 29 29    14.752   13.934   32.7    2.2   355   32.3 
2025-12-14 00:00 UT   17 09 03.1   +09 28 37    14.756   13.940   32.9    2.2   353   32.3 
2025-12-15 00:00 UT   17 09 19.2   +09 27 47    14.760   13.946   33.1    2.2   352   32.3 
2025-12-16 00:00 UT   17 09 35.3   +09 26 60    14.763   13.951   33.3    2.2   350   32.3 
2025-12-17 00:00 UT   17 09 51.4   +09 26 15    14.767   13.957   33.5    2.2   348   32.3 
2025-12-18 00:00 UT   17 10 07.4   +09 25 32    14.770   13.963   33.7    2.2   347   32.3 
2025-12-19 00:00 UT   17 10 23.4   +09 24 52    14.773   13.968   34.0    2.3   345   32.3 

    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.