C/2019 J1 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	5 Apr 2019	17.8	2.480 AU	2.363 AU	19h25m	-16°31'	84.8°	23.7°	262°
Nearest approach	3 Jul 2019	17.4	2.656 AU	1.693 AU	20h29m	-30°43'	156.4°	8.8°	283°
Today	18 Sep 2025	30.3	16.738 AU	16.157 AU	03h27m	-02°28'	123.8°	2.9°	269°

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/2019 J1 (Lemmon) are:

            e (Eccentricity)                : 0.9625850
            q (Perihelion distance)         : 2.4804410
            i (Inclination)                 : 24.52150
            Ω (Longitude of ascending node) : 98.23900
            ω (Argument of perihelion)      : 167.54620
            L (Longitude of perihelion)     : 86.87787
            B (Latitude of perihelion)      : 5.13503
            T (Time of perihelion passage)  : 2458579.25930
            P (Orbital period in years)     : 539.79

            Epoch                           : 2025 Sep 17
            Reference                       : MPEC 2023-A50

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

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 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. (12.00 + 5 log[∆] + 10.00 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
2025-09-18 00:00 UT   03 27 29.0   -02 28 07    16.159   16.736  123.6    2.9   269   30.3 
2025-09-18 06:48 UT   03 27 27.3   -02 28 29    16.157   16.738  123.8    2.9   269   30.3 
2025-09-19 00:00 UT   03 27 22.9   -02 29 26    16.152   16.741  124.5    2.8   270   30.3 
2025-09-20 00:00 UT   03 27 16.6   -02 30 45    16.144   16.747  125.4    2.8   270   30.3 
2025-09-21 00:00 UT   03 27 10.1   -02 32 04    16.137   16.752  126.3    2.8   271   30.3 
2025-09-22 00:00 UT   03 27 03.4   -02 33 23    16.130   16.757  127.2    2.7   271   30.3 
2025-09-23 00:00 UT   03 26 56.5   -02 34 43    16.123   16.762  128.1    2.7   272   30.3 
2025-09-24 00:00 UT   03 26 49.3   -02 36 02    16.117   16.767  129.0    2.7   273   30.3 
2025-09-25 00:00 UT   03 26 42.0   -02 37 21    16.110   16.772  129.9    2.6   273   30.3 
2025-09-26 00:00 UT   03 26 34.5   -02 38 40    16.104   16.777  130.8    2.6   274   30.3 
2025-09-27 00:00 UT   03 26 26.7   -02 39 59    16.098   16.782  131.7    2.6   274   30.3 
2025-09-28 00:00 UT   03 26 18.8   -02 41 17    16.092   16.787  132.6    2.5   275   30.3 

    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.