C/2018 R5 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	28 Sep 2018	19.5	3.738 AU	2.837 AU	22h49m	+23°04'	149.9°	7.7°	132°
Perihelion	10 Jan 2019	20.2	3.637 AU	4.194 AU	22h43m	-06°32'	49.8°	11.9°	67°
Today	23 Oct 2025	29.3	15.218 AU	15.848 AU	11h00m	-44°24'	49.3°	2.8°	242°

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. The light curve is based on the absolute magnitude and slope parameter as calculated from an MPEC, or the latest values provided by the minor planet center. (11.5 + 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 R5 (Lemmon) are:

    e (Eccentricity)                : 0.8417060
    q (Perihelion distance)         : 3.6370480
    i (Inclination)                 : 103.66650
    Ω (Longitude of ascending node) : 171.29000
    ω (Argument of perihelion)      : 178.26870
    L (Longitude of perihelion)     : 171.69917
    B (Latitude of perihelion)      : 1.68227
    T (Time of perihelion passage)  : 2458494.32590
    P (Orbital period in years)     : 110.14

    Epoch                           : 2025 Oct 22
    Reference                       : MPC114603

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-10-22 00:00 UT   11 00 03.3   -44 21 41    15.848   15.212   48.8    2.8   240   29.3 
2025-10-23 00:00 UT   11 00 17.2   -44 23 48    15.848   15.216   49.1    2.8   241   29.3 
2025-10-23 12:47 UT   11 00 24.5   -44 24 57    15.848   15.218   49.3    2.8   242   29.3 
2025-10-24 00:00 UT   11 00 30.9   -44 25 57    15.848   15.220   49.4    2.8   242   29.3 
2025-10-25 00:00 UT   11 00 44.3   -44 28 07    15.848   15.224   49.7    2.9   243   29.3 
2025-10-26 00:00 UT   11 00 57.6   -44 30 19    15.847   15.228   50.1    2.9   244   29.3 
2025-10-27 00:00 UT   11 01 10.5   -44 32 31    15.846   15.233   50.4    2.9   246   29.3 
2025-10-28 00:00 UT   11 01 23.3   -44 34 45    15.845   15.237   50.8    2.9   247   29.3 
2025-10-29 00:00 UT   11 01 35.8   -44 36 60    15.844   15.241   51.1    2.9   248   29.3 
2025-10-30 00:00 UT   11 01 48.0   -44 39 16    15.843   15.245   51.5    2.9   249   29.3 
2025-10-31 00:00 UT   11 02 00.0   -44 41 33    15.841   15.249   51.9    2.9   250   29.3 
2025-11-01 00:00 UT   11 02 11.8   -44 43 51    15.840   15.253   52.3    3.0   251   29.3 
2025-11-02 00:00 UT   11 02 23.3   -44 46 10    15.838   15.258   52.7    3.0   252   29.3 

    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.