C/2020 S8 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	10 Apr 2021	15.7	2.355 AU	1.468 AU	15h04m	+15°11'	144.3°	14.4°	231°
Nearest approach	23 Apr 2021	15.7	2.360 AU	1.410 AU	14h10m	+12°37'	154.8°	10.4°	185°
Today	18 Sep 2025	27.9	13.129 AU	13.001 AU	05h21m	-40°45'	95.1°	4.4°	272°

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.)

The orbital elements of C/2020 S8 (Lemmon) are:

            e (Eccentricity)                : 0.9900890
            q (Perihelion distance)         : 2.3552910
            i (Inclination)                 : 108.54770
            Ω (Longitude of ascending node) : 23.99610
            ω (Argument of perihelion)      : 160.11740
            L (Longitude of perihelion)     : 30.55851
            B (Latitude of perihelion)      : 18.80990
            T (Time of perihelion passage)  : 2459314.79340
            P (Orbital period in years)     : 3663.45

            Epoch                           : 2025 Sep 17
            Reference                       : MPEC 2021-P47

            Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)
        

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. The gray curve is based on the absolute magnitude and slope parameter as calculated from the original MPEC, or the latest values provided by the MPC (12.50 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 11.19 + 5 log[∆] + 10.00 log[r]).

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-09-18 00:00 UT   05 21 52.1   -40 44 24    13.001   13.128   95.0    4.4   272   27.9 
2025-09-18 05:26 UT   05 21 50.7   -40 45 14    13.001   13.129   95.1    4.4   272   27.9 
2025-09-19 00:00 UT   05 21 45.9   -40 48 06    12.999   13.134   95.5    4.4   273   27.9 
2025-09-20 00:00 UT   05 21 39.2   -40 51 47    12.998   13.140   95.9    4.4   274   27.9 
2025-09-21 00:00 UT   05 21 32.2   -40 55 28    12.996   13.146   96.4    4.4   274   27.9 
2025-09-22 00:00 UT   05 21 24.7   -40 59 08    12.995   13.152   96.8    4.3   275   28.0 
2025-09-23 00:00 UT   05 21 16.8   -41 02 49    12.993   13.158   97.2    4.3   276   28.0 
2025-09-24 00:00 UT   05 21 08.4   -41 06 28    12.992   13.164   97.7    4.3   277   28.0 
2025-09-25 00:00 UT   05 20 59.7   -41 10 07    12.990   13.170   98.1    4.3   278   28.0 
2025-09-26 00:00 UT   05 20 50.5   -41 13 46    12.989   13.176   98.5    4.3   279   28.0 
2025-09-27 00:00 UT   05 20 40.9   -41 17 23    12.988   13.182   99.0    4.3   280   28.0 
2025-09-28 00:00 UT   05 20 30.8   -41 21 00    12.987   13.188   99.4    4.3   281   28.0 

    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.