C/2018 R3 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	23 May 2019	11.7	1.306 AU	1.919 AU	03h35m	+59°43'	39.4°	29.5°	351°
Perihelion	7 Jun 2019	11.6	1.286 AU	1.960 AU	05h44m	+57°57'	36.0°	27.7°	17°
Today	28 Dec 2025	36.2	18.480 AU	18.664 AU	10h23m	-70°48'	77.7°	3.0°	307°

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. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 8.3 + 5 log[∆] + 17.0 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 R3 (Lemmon) are:

    e (Eccentricity)                : 0.9993050
    q (Perihelion distance)         : 1.2860390
    i (Inclination)                 : 69.68060
    Ω (Longitude of ascending node) : 324.31240
    ω (Argument of perihelion)      : 112.84610
    L (Longitude of perihelion)     : 284.81618
    B (Latitude of perihelion)      : 59.79196
    T (Time of perihelion passage)  : 2458642.36380
    P (Orbital period in years)     : 79598.34

    Epoch                           : 2025 Nov 12
    Reference                       : MPC118841

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-12-27 00:00 UT   10 23 41.1   -70 43 27    18.664   18.469   77.1    3.0   305   36.2 
2025-12-28 00:00 UT   10 23 21.9   -70 46 17    18.664   18.475   77.4    3.0   306   36.2 
2025-12-28 22:19 UT   10 23 03.5   -70 48 54    18.664   18.480   77.7    3.0   307   36.2 
2025-12-29 00:00 UT   10 23 02.1   -70 49 06    18.664   18.480   77.7    3.0   307   36.2 
2025-12-30 00:00 UT   10 22 41.6   -70 51 53    18.663   18.486   78.1    3.0   308   36.2 
2025-12-31 00:00 UT   10 22 20.6   -70 54 37    18.663   18.491   78.4    3.0   309   36.2 
2026-01-01 00:00 UT   10 21 58.9   -70 57 19    18.663   18.497   78.7    3.0   310   36.2 
2026-01-02 00:00 UT   10 21 36.6   -70 59 59    18.662   18.502   79.1    3.0   311   36.2 
2026-01-03 00:00 UT   10 21 13.7   -71 02 36    18.662   18.507   79.4    3.0   312   36.2 
2026-01-04 00:00 UT   10 20 50.2   -71 05 11    18.661   18.513   79.8    3.0   313   36.2 
2026-01-05 00:00 UT   10 20 26.1   -71 07 44    18.661   18.518   80.1    3.0   314   36.2 
2026-01-06 00:00 UT   10 20 01.4   -71 10 14    18.660   18.524   80.5    3.0   316   36.2 
2026-01-07 00:00 UT   10 19 36.1   -71 12 41    18.660   18.529   80.8    3.0   317   36.2 

    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.