C/2018 B1 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	12 Dec 2017	17.5	5.194 AU	4.249 AU	04h58m	+40°37'	161.9°	3.4°	164°
Perihelion	27 Mar 2018	18.1	5.134 AU	5.685 AU	03h21m	+33°40'	52.2°	8.8°	63°
Today	6 Nov 2025	26.1	17.997 AU	18.100 AU	20h36m	-19°49'	82.5°	3.1°	76°

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. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 7.3 + 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/2018 B1 (Lemmon) are:

    e (Eccentricity)                : 0.9984870
    q (Perihelion distance)         : 5.1337890
    i (Inclination)                 : 162.42000
    Ω (Longitude of ascending node) : 133.19100
    ω (Argument of perihelion)      : 68.41520
    L (Longitude of perihelion)     : 65.72962
    B (Latitude of perihelion)      : 16.31133
    T (Time of perihelion passage)  : 2458204.52710
    P (Orbital period in years)     : 197650.82

    Epoch                           : 2023 Apr 14
    Reference                       : MPEC 2022-O08

    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
2025-11-05 00:00 UT   20 36 04.5   -19 49 40    18.069   17.991   83.9    3.1    76   26.1 
2025-11-06 00:00 UT   20 36 04.3   -19 49 47    18.091   17.995   82.9    3.1    76   26.1 
2025-11-06 09:30 UT   20 36 04.3   -19 49 50    18.100   17.997   82.5    3.1    76   26.1 
2025-11-07 00:00 UT   20 36 04.4   -19 49 54    18.114   18.000   81.9    3.1    76   26.1 
2025-11-08 00:00 UT   20 36 04.6   -19 49 59    18.136   18.005   80.9    3.1    76   26.1 
2025-11-09 00:00 UT   20 36 05.1   -19 50 04    18.158   18.010   79.8    3.1    76   26.1 
2025-11-10 00:00 UT   20 36 05.8   -19 50 08    18.180   18.015   78.8    3.1    76   26.1 
2025-11-11 00:00 UT   20 36 06.8   -19 50 12    18.202   18.020   77.8    3.1    76   26.1 
2025-11-12 00:00 UT   20 36 08.0   -19 50 14    18.223   18.025   76.8    3.1    76   26.1 
2025-11-13 00:00 UT   20 36 09.4   -19 50 15    18.245   18.029   75.8    3.1    76   26.1 
2025-11-14 00:00 UT   20 36 11.0   -19 50 16    18.267   18.034   74.8    3.0    76   26.1 
2025-11-15 00:00 UT   20 36 12.9   -19 50 16    18.289   18.039   73.8    3.0    76   26.1 
2025-11-16 00:00 UT   20 36 15.0   -19 50 15    18.310   18.044   72.8    3.0    76   26.1 

    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.