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	18 Mar 2026	26.4	18.634 AU	19.293 AU	20h53m	-19°03'	47.4°	2.3°	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
2026-03-17 00:00 UT   20 53 19.7   -19 03 39    19.307   18.625   45.6    2.2   253   26.4 
2026-03-18 00:00 UT   20 53 26.6   -19 03 25    19.300   18.630   46.6    2.2   253   26.4 
2026-03-18 20:32 UT   20 53 32.4   -19 03 13    19.293   18.634   47.4    2.3   253   26.4 
2026-03-19 00:00 UT   20 53 33.3   -19 03 11    19.292   18.635   47.5    2.3   253   26.4 
2026-03-20 00:00 UT   20 53 39.9   -19 02 59    19.284   18.640   48.5    2.3   253   26.4 
2026-03-21 00:00 UT   20 53 46.4   -19 02 46    19.276   18.645   49.5    2.3   253   26.4 
2026-03-22 00:00 UT   20 53 52.7   -19 02 35    19.267   18.649   50.4    2.4   253   26.4 
2026-03-23 00:00 UT   20 53 58.8   -19 02 24    19.259   18.654   51.4    2.4   253   26.4 
2026-03-24 00:00 UT   20 54 04.8   -19 02 14    19.250   18.659   52.4    2.4   253   26.4 
2026-03-25 00:00 UT   20 54 10.6   -19 02 04    19.241   18.664   53.4    2.5   253   26.4 
2026-03-26 00:00 UT   20 54 16.2   -19 01 56    19.232   18.668   54.3    2.5   253   26.4 
2026-03-27 00:00 UT   20 54 21.7   -19 01 48    19.223   18.673   55.3    2.5   253   26.4 
2026-03-28 00:00 UT   20 54 26.9   -19 01 41    19.213   18.678   56.3    2.5   253   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.