C/2018 R3 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	24 May 2019	11.7	1.304 AU	1.918 AU	03h35m	+59°43'	39.4°	29.5°	350°
Perihelion	7 Jun 2019	11.6	1.285 AU	1.959 AU	05h44m	+57°56'	36.0°	27.7°	17°
Today	26 Jul 2025	35.7	17.622 AU	17.663 AU	09h44m	-65°03'	86.0°	3.3°	160°

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 R3 (Lemmon) are:

            e (Eccentricity)                : 0.9992890
            q (Perihelion distance)         : 1.2847380
            i (Inclination)                 : 69.68540
            Ω (Longitude of ascending node) : 324.34760
            ω (Argument of perihelion)      : 112.81610
            L (Longitude of perihelion)     : 284.81656
            B (Latitude of perihelion)      : 59.81672
            T (Time of perihelion passage)  : 2458642.47910
            P (Orbital period in years)     : 76809.94

            Epoch                           : 2025 Jul 24
            Reference                       : MPC118841

            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 (9.50 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 8.32 + 5 log[∆] + 16.95 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
2025-07-26 00:00 UT   09 44 20.0   -65 03 21    17.662   17.622   86.1    3.3   160   35.7 
2025-07-26 01:58 UT   09 44 22.3   -65 03 18    17.663   17.622   86.0    3.3   160   35.7 
2025-07-27 00:00 UT   09 44 47.9   -65 02 48    17.674   17.627   85.7    3.3   161   35.7 
2025-07-28 00:00 UT   09 45 15.9   -65 02 18    17.685   17.633   85.4    3.3   162   35.7 
2025-07-29 00:00 UT   09 45 44.0   -65 01 52    17.697   17.638   85.0    3.3   163   35.7 
2025-07-30 00:00 UT   09 46 12.3   -65 01 28    17.709   17.644   84.7    3.3   163   35.7 
2025-07-31 00:00 UT   09 46 40.6   -65 01 06    17.721   17.649   84.3    3.3   164   35.7 
2025-08-01 00:00 UT   09 47 09.0   -65 00 48    17.732   17.655   84.0    3.3   165   35.7 
2025-08-02 00:00 UT   09 47 37.5   -65 00 33    17.744   17.661   83.6    3.3   166   35.7 
2025-08-03 00:00 UT   09 48 06.1   -65 00 20    17.756   17.666   83.3    3.3   167   35.7 
2025-08-04 00:00 UT   09 48 34.7   -65 00 11    17.767   17.672   82.9    3.3   167   35.7 
2025-08-05 00:00 UT   09 49 03.4   -65 00 04    17.779   17.677   82.6    3.3   168   35.7 

    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.