C/2018 U1 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	18 Jun 2021	15.2	5.095 AU	4.133 AU	17h19m	-03°37'	159.1°	4.1°	161°
Perihelion	2 Nov 2021	15.9	4.985 AU	5.818 AU	16h31m	-22°10'	30.1°	5.7°	99°
Today	11 Aug 2025	20.1	10.830 AU	11.193 AU	08h04m	-48°54'	66.6°	4.9°	201°

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 U1 (Lemmon) are:

            e (Eccentricity)                : 1.0000060
            q (Perihelion distance)         : 4.9852640
            i (Inclination)                 : 108.32580
            Ω (Longitude of ascending node) : 75.51340
            ω (Argument of perihelion)      : 180.34090
            L (Longitude of perihelion)     : 75.40621
            B (Latitude of perihelion)      : -0.32361
            T (Time of perihelion passage)  : 2459520.54230

            Epoch                           : 2025 Aug 09
            Reference                       : MPC184408

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

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 (5.00 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 6.31 + 5 log[∆] + 8.25 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
2025-08-11 00:00 UT   08 04 47.1   -48 54 52    11.192   10.829   66.6    4.9   201   20.1 
2025-08-11 02:05 UT   08 04 49.1   -48 54 57    11.193   10.830   66.6    4.9   201   20.1 
2025-08-12 00:00 UT   08 05 09.6   -48 55 54    11.199   10.835   66.5    4.9   201   20.1 
2025-08-13 00:00 UT   08 05 31.9   -48 57 00    11.205   10.840   66.4    4.9   202   20.1 
2025-08-14 00:00 UT   08 05 54.0   -48 58 11    11.212   10.846   66.4    4.9   203   20.1 
2025-08-15 00:00 UT   08 06 15.9   -48 59 26    11.218   10.851   66.3    4.9   204   20.1 
2025-08-16 00:00 UT   08 06 37.6   -49 00 44    11.224   10.857   66.3    4.9   205   20.1 
2025-08-17 00:00 UT   08 06 59.1   -49 02 07    11.230   10.862   66.2    4.9   206   20.1 
2025-08-18 00:00 UT   08 07 20.4   -49 03 34    11.236   10.867   66.2    4.9   207   20.1 
2025-08-19 00:00 UT   08 07 41.5   -49 05 04    11.242   10.873   66.2    4.9   208   20.1 
2025-08-20 00:00 UT   08 08 02.3   -49 06 39    11.248   10.878   66.1    4.9   209   20.1 
2025-08-21 00:00 UT   08 08 22.9   -49 08 18    11.254   10.884   66.1    4.9   210   20.1 

    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.