C/2018 B1 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	12 Dec 2017	17.5	5.194 AU	4.249 AU	04h58m	+40°37'	161.9°	3.4°	164°
Perihelion	27 Mar 2018	18.1	5.134 AU	5.685 AU	03h21m	+33°40'	52.2°	8.8°	63°
Today	4 Jul 2025	25.7	17.388 AU	16.503 AU	21h00m	-17°54'	149.6°	1.7°	255°

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.)

The orbital elements of C/2018 B1 (Lemmon) are:

            e (Eccentricity)                : 0.9984870
            q (Perihelion distance)         : 5.1337890
            i (Inclination)                 : 162.42000
            Ω (Longitude of ascending node) : 133.19100
            ω (Argument of perihelion)      : 68.41520
            L (Longitude of perihelion)     : 65.72962
            B (Latitude of perihelion)      : 16.31133
            T (Time of perihelion passage)  : 2458204.52710
            P (Orbital period in years)     : 197650.82

            Epoch                           : 2023 Apr 14
            Reference                       : MPEC 2022-O08

            Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)
        

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. The gray curve is based on the absolute magnitude and slope parameter as calculated from the original MPEC, or the latest values provided by the MPC (9.00 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 7.25 + 5 log[∆] + 10.00 log[r]).

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-07-04 00:00 UT   21 00 16.8   -17 54 15    16.503   17.387  149.6    1.7   255   25.7 
2025-07-04 00:53 UT   21 00 16.2   -17 54 18    16.503   17.388  149.6    1.7   255   25.7 
2025-07-05 00:00 UT   21 00 02.1   -17 55 31    16.499   17.392  150.6    1.6   255   25.7 
2025-07-06 00:00 UT   20 59 47.2   -17 56 47    16.496   17.397  151.6    1.6   255   25.7 
2025-07-07 00:00 UT   20 59 32.3   -17 58 03    16.493   17.402  152.6    1.5   255   25.7 
2025-07-08 00:00 UT   20 59 17.2   -17 59 20    16.490   17.407  153.6    1.5   255   25.7 
2025-07-09 00:00 UT   20 59 02.0   -18 00 37    16.487   17.412  154.7    1.4   256   25.7 
2025-07-10 00:00 UT   20 58 46.7   -18 01 55    16.485   17.417  155.7    1.4   256   25.7 
2025-07-11 00:00 UT   20 58 31.2   -18 03 13    16.483   17.422  156.7    1.3   256   25.7 
2025-07-12 00:00 UT   20 58 15.7   -18 04 31    16.481   17.426  157.7    1.3   256   25.7 
2025-07-13 00:00 UT   20 58 00.1   -18 05 49    16.480   17.431  158.7    1.2   256   25.7 
2025-07-14 00:00 UT   20 57 44.4   -18 07 08    16.479   17.436  159.7    1.2   256   25.7 

    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.