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	23 Jul 2026	26.4	19.240 AU	18.231 AU	20h41m	-20°19'	172.9°	0.4°	271°

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
2026-07-22 00:00 UT   20 42 26.7   -20 16 57    18.226   19.231  171.0    0.5   268   26.4 
2026-07-23 00:00 UT   20 42 11.8   -20 18 04    18.229   19.236  172.0    0.4   269   26.4 
2026-07-23 23:38 UT   20 41 57.0   -20 19 11    18.231   19.240  172.9    0.4   271   26.4 
2026-07-24 00:00 UT   20 41 56.7   -20 19 12    18.231   19.240  173.0    0.4   271   26.4 
2026-07-25 00:00 UT   20 41 41.7   -20 20 19    18.234   19.245  173.9    0.3   274   26.4 
2026-07-26 00:00 UT   20 41 26.6   -20 21 26    18.238   19.250  174.9    0.3   278   26.4 
2026-07-27 00:00 UT   20 41 11.5   -20 22 33    18.241   19.255  175.8    0.2   284   26.4 
2026-07-28 00:00 UT   20 40 56.5   -20 23 40    18.245   19.259  176.6    0.2   292   26.4 
2026-07-29 00:00 UT   20 40 41.3   -20 24 47    18.249   19.264  177.4    0.1   305   26.4 
2026-07-30 00:00 UT   20 40 26.2   -20 25 53    18.254   19.269  177.9    0.1   327   26.4 
2026-07-31 00:00 UT   20 40 11.1   -20 26 59    18.259   19.274  177.9    0.1   355   26.4 
2026-08-01 00:00 UT   20 39 56.0   -20 28 05    18.264   19.278  177.6    0.1    19   26.4 
2026-08-02 00:00 UT   20 39 40.9   -20 29 11    18.269   19.283  176.9    0.2    35   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.