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	15 Jul 2025	35.6	17.565 AU	17.542 AU	09h39m	-65°11'	89.6°	3.3°	152°

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)                : 0.9992880
            q (Perihelion distance)         : 1.2846630
            i (Inclination)                 : 69.68580
            Ω (Longitude of ascending node) : 324.35070
            ω (Argument of perihelion)      : 112.81400
            L (Longitude of perihelion)     : 284.81731
            B (Latitude of perihelion)      : 59.81850
            T (Time of perihelion passage)  : 2458642.48410
            P (Orbital period in years)     : 76641.47

            Epoch                           : 2025 Jul 14
            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
2025-07-15 00:00 UT   09 39 22.5   -65 12 29    17.532   17.560   89.9    3.3   152   35.6 
2025-07-15 20:26 UT   09 39 44.9   -65 11 35    17.542   17.565   89.6    3.3   152   35.6 
2025-07-16 00:00 UT   09 39 48.8   -65 11 25    17.544   17.566   89.5    3.3   153   35.6 
2025-07-17 00:00 UT   09 40 15.2   -65 10 24    17.556   17.572   89.2    3.3   153   35.6 
2025-07-18 00:00 UT   09 40 41.8   -65 09 26    17.568   17.577   88.9    3.3   154   35.6 
2025-07-19 00:00 UT   09 41 08.5   -65 08 30    17.579   17.583   88.5    3.3   155   35.6 
2025-07-20 00:00 UT   09 41 35.4   -65 07 38    17.591   17.588   88.2    3.3   156   35.7 
2025-07-21 00:00 UT   09 42 02.5   -65 06 48    17.603   17.594   87.8    3.3   156   35.7 
2025-07-22 00:00 UT   09 42 29.7   -65 06 01    17.615   17.599   87.5    3.3   157   35.7 
2025-07-23 00:00 UT   09 42 57.1   -65 05 16    17.626   17.605   87.1    3.3   158   35.7 
2025-07-24 00:00 UT   09 43 24.6   -65 04 35    17.638   17.611   86.8    3.3   159   35.7 
2025-07-25 00:00 UT   09 43 52.3   -65 03 57    17.650   17.616   86.4    3.3   160   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.