C/2018 EF9 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	13 Mar 2018	14.8	1.816 AU	1.060 AU	14h01m	+48°44'	124.3°	26.9°	227°
Perihelion	20 May 2018	15.2	1.564 AU	1.684 AU	04h56m	+85°13'	65.5°	36.1°	18°
Today	11 May 2025	31.3	18.986 AU	19.468 AU	01h09m	-34°36'	60.2°	2.6°	214°

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 EF9 (Lemmon) are:

            e (Eccentricity)                : 0.9963920
            q (Perihelion distance)         : 1.5637500
            i (Inclination)                 : 84.65510
            Ω (Longitude of ascending node) : 172.58050
            ω (Argument of perihelion)      : 72.64170
            L (Longitude of perihelion)     : 189.17480
            B (Latitude of perihelion)      : 71.86168
            T (Time of perihelion passage)  : 2458258.93940
            P (Orbital period in years)     : 9023.00

            Epoch                           : 2023 Sep 24
            Reference                       : MPEC 2023-CD7

            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 (18.00 + 5 log[∆] + 5.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 12.11 + 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
2025-05-11 00:00 UT   01 09 44.2   -34 36 24    19.471   18.983   59.8    2.6   214   31.3 
2025-05-11 12:32 UT   01 09 50.6   -34 36 41    19.468   18.986   60.2    2.6   214   31.3 
2025-05-12 00:00 UT   01 09 56.5   -34 36 58    19.466   18.989   60.5    2.7   215   31.3 
2025-05-13 00:00 UT   01 10 08.7   -34 37 34    19.460   18.994   61.1    2.7   215   31.3 
2025-05-14 00:00 UT   01 10 20.7   -34 38 13    19.455   18.999   61.8    2.7   216   31.3 
2025-05-15 00:00 UT   01 10 32.7   -34 38 53    19.450   19.005   62.5    2.7   217   31.3 
2025-05-16 00:00 UT   01 10 44.5   -34 39 36    19.444   19.010   63.2    2.7   217   31.3 
2025-05-17 00:00 UT   01 10 56.3   -34 40 21    19.439   19.015   63.8    2.7   218   31.3 
2025-05-18 00:00 UT   01 11 07.8   -34 41 08    19.433   19.020   64.5    2.8   219   31.3 
2025-05-19 00:00 UT   01 11 19.3   -34 41 57    19.427   19.026   65.2    2.8   220   31.3 
2025-05-20 00:00 UT   01 11 30.6   -34 42 48    19.421   19.031   65.9    2.8   220   31.3 
2025-05-21 00:00 UT   01 11 41.8   -34 43 41    19.415   19.036   66.6    2.8   221   31.3 

    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.