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C/2018 U1 (Lemmon)
ephemeris date magn radius delta ra dec elong phase PA
Nearest approach18 Jun 202115.25.093 AU4.132 AU 17h19m-03°37'159.1°4.1°161°
Perihelion1 Nov 202115.94.984 AU5.816 AU 16h31m-22°09'30.3°5.8°99°
Today23 Oct 202520.311.231 AU11.410 AU 08h17m-52°30'77.1°5.0°272°
C/2018 U1 (Lemmon)- 2025-10-23
astro.vanbuitenen.nl


 
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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 6.3 + 5 log[∆] + 8.3 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 U1 (Lemmon) are: 

    e (Eccentricity)                : 0.9998230
    q (Perihelion distance)         : 4.9842390
    i (Inclination)                 : 108.32610
    Ω (Longitude of ascending node) : 75.51080
    ω (Argument of perihelion)      : 180.32370
    L (Longitude of perihelion)     : 75.40902
    B (Latitude of perihelion)      : -0.30728
    T (Time of perihelion passage)  : 2459520.39910

    Epoch                           : 2025 Oct 23
    Reference                       : MPC184408

    Classification(s):              : Nearly isotropic; New (a > 10000 AU)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-10-22 00:00 UT   08 17 43.5   -52 23 01    11.410   11.220   76.5    4.9   270   20.3 
2025-10-23 00:00 UT   08 17 37.2   -52 26 57    11.410   11.225   76.8    5.0   271   20.3 
2025-10-23 23:41 UT   08 17 30.4   -52 30 50    11.410   11.231   77.1    5.0   272   20.3 
2025-10-24 00:00 UT   08 17 30.3   -52 30 53    11.410   11.231   77.1    5.0   272   20.3 
2025-10-25 00:00 UT   08 17 22.7   -52 34 49    11.409   11.236   77.5    5.0   273   20.3 
2025-10-26 00:00 UT   08 17 14.6   -52 38 44    11.409   11.242   77.8    5.0   274   20.3 
2025-10-27 00:00 UT   08 17 05.8   -52 42 38    11.409   11.247   78.1    5.0   275   20.3 
2025-10-28 00:00 UT   08 16 56.5   -52 46 33    11.409   11.252   78.5    5.0   276   20.3 
2025-10-29 00:00 UT   08 16 46.5   -52 50 26    11.408   11.258   78.8    5.0   277   20.3 
2025-10-30 00:00 UT   08 16 35.9   -52 54 19    11.408   11.263   79.1    5.0   278   20.3 
2025-10-31 00:00 UT   08 16 24.7   -52 58 11    11.407   11.269   79.5    5.0   279   20.3 
2025-11-01 00:00 UT   08 16 12.9   -53 02 02    11.407   11.274   79.8    5.0   280   20.3 
2025-11-02 00:00 UT   08 16 00.5   -53 05 52    11.406   11.279   80.1    5.0   281   20.3 




    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.

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