C/2018 B1 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	12 Dec 2017	17.6	5.217 AU	4.272 AU	04h58m	+40°34'	162.0°	3.3°	164°
Perihelion	28 Mar 2018	18.2	5.155 AU	5.724 AU	03h21m	+33°36'	51.0°	8.7°	63°
Today	18 Jun 2026	26.4	19.073 AU	18.310 AU	20h49m	-19°40'	137.5°	2.1°	256°

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)                : 0.9997750
    q (Perihelion distance)         : 5.1551400
    i (Inclination)                 : 162.46560
    Ω (Longitude of ascending node) : 133.18880
    ω (Argument of perihelion)      : 68.63750
    L (Longitude of perihelion)     : 65.49226
    B (Latitude of perihelion)      : 16.29476
    T (Time of perihelion passage)  : 2458205.71800

    Epoch                           : 2026 May 29
    Reference                       : MPC194155

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-06-17 00:00 UT   20 50 19.2   -19 38 57    18.322   19.065  135.8    2.1   256   26.4 
2026-06-18 00:00 UT   20 50 07.9   -19 39 57    18.315   19.069  136.8    2.1   256   26.4 
2026-06-18 16:38 UT   20 49 59.9   -19 40 38    18.310   19.073  137.5    2.1   256   26.4 
2026-06-19 00:00 UT   20 49 56.4   -19 40 57    18.308   19.074  137.8    2.0   256   26.4 
2026-06-20 00:00 UT   20 49 44.7   -19 41 57    18.302   19.079  138.8    2.0   257   26.4 
2026-06-21 00:00 UT   20 49 32.8   -19 42 58    18.295   19.084  139.8    2.0   257   26.4 
2026-06-22 00:00 UT   20 49 20.9   -19 43 60    18.289   19.088  140.8    1.9   257   26.4 
2026-06-23 00:00 UT   20 49 08.7   -19 45 02    18.283   19.093  141.9    1.9   257   26.4 
2026-06-24 00:00 UT   20 48 56.4   -19 46 04    18.277   19.098  142.9    1.8   257   26.4 
2026-06-25 00:00 UT   20 48 44.0   -19 47 07    18.272   19.103  143.9    1.8   257   26.4 
2026-06-26 00:00 UT   20 48 31.4   -19 48 10    18.267   19.107  144.9    1.8   257   26.4 
2026-06-27 00:00 UT   20 48 18.7   -19 49 13    18.262   19.112  145.9    1.7   257   26.4 
2026-06-28 00:00 UT   20 48 05.9   -19 50 17    18.257   19.117  146.9    1.7   257   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.