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	7 May 2026	26.4	18.872 AU	18.744 AU	20h55m	-19°08'	95.7°	3.0°	254°

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
2026-05-06 00:00 UT   20 55 21.1   -19 07 54    18.763   18.864   94.2    3.1   254   26.4 
2026-05-07 00:00 UT   20 55 18.3   -19 08 22    18.750   18.869   95.2    3.1   254   26.4 
2026-05-07 11:37 UT   20 55 16.8   -19 08 35    18.744   18.872   95.7    3.0   254   26.4 
2026-05-08 00:00 UT   20 55 15.2   -19 08 50    18.738   18.874   96.2    3.0   254   26.4 
2026-05-09 00:00 UT   20 55 11.9   -19 09 19    18.726   18.879   97.2    3.0   254   26.4 
2026-05-10 00:00 UT   20 55 08.5   -19 09 49    18.713   18.884   98.2    3.0   254   26.4 
2026-05-11 00:00 UT   20 55 04.7   -19 10 20    18.701   18.888   99.1    3.0   254   26.4 
2026-05-12 00:00 UT   20 55 00.8   -19 10 52    18.689   18.893  100.1    3.0   254   26.4 
2026-05-13 00:00 UT   20 54 56.6   -19 11 25    18.677   18.898  101.1    3.0   254   26.4 
2026-05-14 00:00 UT   20 54 52.3   -19 11 59    18.665   18.903  102.1    3.0   254   26.4 
2026-05-15 00:00 UT   20 54 47.7   -19 12 33    18.653   18.907  103.1    3.0   254   26.4 
2026-05-16 00:00 UT   20 54 42.8   -19 13 09    18.641   18.912  104.1    3.0   254   26.4 
2026-05-17 00:00 UT   20 54 37.8   -19 13 45    18.629   18.917  105.0    3.0   255   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.