C/2018 U1 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	18 Jun 2021	15.2	5.093 AU	4.131 AU	17h19m	-03°37'	159.1°	4.1°	161°
Perihelion	1 Nov 2021	15.9	4.984 AU	5.816 AU	16h31m	-22°08'	30.3°	5.8°	99°
Today	16 Nov 2025	20.3	11.356 AU	11.396 AU	08h11m	-53°57'	85.2°	5.0°	296°

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)                : 0.9997710
    q (Perihelion distance)         : 4.9839640
    i (Inclination)                 : 108.32620
    Ω (Longitude of ascending node) : 75.50960
    ω (Argument of perihelion)      : 180.31880
    L (Longitude of perihelion)     : 75.40936
    B (Latitude of perihelion)      : -0.30263
    T (Time of perihelion passage)  : 2459520.35680

    Epoch                           : 2025 Nov 15
    Reference                       : MPC184408

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-11-15 00:00 UT   08 12 22.3   -53 53 25    11.397   11.350   84.8    5.0   294   20.3 
2025-11-16 00:00 UT   08 12 01.1   -53 56 50    11.396   11.355   85.1    5.0   295   20.3 
2025-11-16 05:58 UT   08 11 55.7   -53 57 41    11.396   11.356   85.2    5.0   296   20.3 
2025-11-17 00:00 UT   08 11 39.3   -54 00 13    11.395   11.361   85.5    5.0   296   20.3 
2025-11-18 00:00 UT   08 11 16.9   -54 03 33    11.394   11.366   85.8    5.0   297   20.3 
2025-11-19 00:00 UT   08 10 53.9   -54 06 50    11.393   11.371   86.2    5.0   298   20.3 
2025-11-20 00:00 UT   08 10 30.2   -54 10 05    11.393   11.377   86.6    5.0   299   20.3 
2025-11-21 00:00 UT   08 10 06.0   -54 13 17    11.392   11.382   86.9    5.0   300   20.3 
2025-11-22 00:00 UT   08 09 41.1   -54 16 25    11.391   11.388   87.3    5.0   302   20.3 
2025-11-23 00:00 UT   08 09 15.7   -54 19 31    11.390   11.393   87.7    5.0   303   20.3 
2025-11-24 00:00 UT   08 08 49.6   -54 22 33    11.389   11.398   88.0    5.0   304   20.3 
2025-11-25 00:00 UT   08 08 23.0   -54 25 31    11.388   11.404   88.4    5.0   305   20.3 
2025-11-26 00:00 UT   08 07 55.7   -54 28 27    11.387   11.409   88.8    5.0   306   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.