C/2018 B1 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	12 Dec 2017	17.6	5.216 AU	4.271 AU	04h58m	+40°35'	162.0°	3.4°	164°
Perihelion	27 Mar 2018	18.2	5.155 AU	5.720 AU	03h21m	+33°36'	51.3°	8.7°	63°
Today	9 Apr 2026	26.4	18.740 AU	19.079 AU	20h55m	-19°01'	68.8°	2.9°	253°

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)                : 0.9996390
    q (Perihelion distance)         : 5.1549510
    i (Inclination)                 : 162.46430
    Ω (Longitude of ascending node) : 133.18840
    ω (Argument of perihelion)      : 68.62950
    L (Longitude of perihelion)     : 65.50028
    B (Latitude of perihelion)      : 16.29504
    T (Time of perihelion passage)  : 2458205.41360

    Epoch                           : 2026 Mar 16
    Reference                       : MPEC 2026-E44

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-04-08 00:00 UT   20 55 13.2   -19 01 13    19.100   18.731   66.9    2.8   253   26.4 
2026-04-09 00:00 UT   20 55 16.3   -19 01 16    19.089   18.735   67.9    2.8   253   26.4 
2026-04-09 21:44 UT   20 55 18.9   -19 01 19    19.079   18.740   68.8    2.9   253   26.4 
2026-04-10 00:00 UT   20 55 19.2   -19 01 19    19.078   18.740   68.9    2.9   253   26.4 
2026-04-11 00:00 UT   20 55 21.9   -19 01 23    19.066   18.745   69.8    2.9   253   26.4 
2026-04-12 00:00 UT   20 55 24.3   -19 01 28    19.055   18.750   70.8    2.9   253   26.4 
2026-04-13 00:00 UT   20 55 26.6   -19 01 34    19.043   18.755   71.8    2.9   253   26.4 
2026-04-14 00:00 UT   20 55 28.7   -19 01 41    19.032   18.759   72.8    2.9   253   26.4 
2026-04-15 00:00 UT   20 55 30.6   -19 01 48    19.020   18.764   73.7    2.9   254   26.4 
2026-04-16 00:00 UT   20 55 32.3   -19 01 57    19.008   18.769   74.7    3.0   254   26.4 
2026-04-17 00:00 UT   20 55 33.7   -19 02 06    18.996   18.774   75.7    3.0   254   26.4 
2026-04-18 00:00 UT   20 55 35.0   -19 02 16    18.984   18.778   76.6    3.0   254   26.4 
2026-04-19 00:00 UT   20 55 36.1   -19 02 27    18.972   18.783   77.6    3.0   254   26.4 

    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.