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	23 Nov 2025	26.2	18.080 AU	18.469 AU	20h36m	-19°49'	65.3°	2.8°	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
2025-11-22 00:00 UT   20 36 32.0   -19 49 53    18.438   18.073   66.9    2.9    76   26.1 
2025-11-23 00:00 UT   20 36 35.5   -19 49 47    18.459   18.078   65.9    2.9    76   26.2 
2025-11-23 12:36 UT   20 36 37.5   -19 49 43    18.469   18.080   65.3    2.8    76   26.2 
2025-11-24 00:00 UT   20 36 39.3   -19 49 40    18.479   18.083   64.9    2.8    76   26.2 
2025-11-25 00:00 UT   20 36 43.3   -19 49 32    18.500   18.087   63.9    2.8    76   26.2 
2025-11-26 00:00 UT   20 36 47.5   -19 49 23    18.520   18.092   62.9    2.8    76   26.2 
2025-11-27 00:00 UT   20 36 51.8   -19 49 14    18.541   18.097   61.9    2.8    76   26.2 
2025-11-28 00:00 UT   20 36 56.4   -19 49 04    18.561   18.102   60.9    2.7    76   26.2 
2025-11-29 00:00 UT   20 37 01.2   -19 48 53    18.581   18.107   59.9    2.7    76   26.2 
2025-11-30 00:00 UT   20 37 06.1   -19 48 42    18.601   18.112   58.9    2.7    76   26.2 
2025-12-01 00:00 UT   20 37 11.3   -19 48 30    18.620   18.116   57.9    2.6    76   26.2 
2025-12-02 00:00 UT   20 37 16.6   -19 48 18    18.640   18.121   56.9    2.6    76   26.2 
2025-12-03 00:00 UT   20 37 22.1   -19 48 04    18.659   18.126   55.9    2.6    76   26.2 

    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.