C/2024 B2 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	5 Oct 2023	20.8	4.078 AU	4.449 AU	11h07m	+53°54'	62.1°	12.5°	332°
Nearest approach	21 Jan 2024	20.4	4.179 AU	3.377 AU	09h11m	+58°26'	140.0°	8.7°	203°
Today	6 May 2025	23.6	6.227 AU	6.692 AU	06h45m	+02°35'	58.6°	8.0°	108°

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/2024 B2 (Lemmon) are:

            e (Eccentricity)                : 0.9982360
            q (Perihelion distance)         : 4.0780830
            i (Inclination)                 : 99.86430
            Ω (Longitude of ascending node) : 294.38370
            ω (Argument of perihelion)      : 130.34220
            L (Longitude of perihelion)     : 305.78763
            B (Latitude of perihelion)      : 48.67046
            T (Time of perihelion passage)  : 2460223.45140
            P (Orbital period in years)     : 111156.85

            Epoch                           : 2025 May 04
            Reference                       : MPEC 2025-A40

            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. (11.50 + 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
2025-05-06 00:00 UT   06 44 54.9   +02 35 47     6.685    6.225   58.9    8.0   108   23.6 
2025-05-06 08:49 UT   06 45 00.8   +02 35 07     6.692    6.227   58.6    8.0   108   23.6 
2025-05-07 00:00 UT   06 45 11.2   +02 33 58     6.704    6.231   58.1    7.9   108   23.6 
2025-05-08 00:00 UT   06 45 27.9   +02 32 08     6.723    6.237   57.3    7.8   109   23.6 
2025-05-09 00:00 UT   06 45 45.0   +02 30 15     6.742    6.242   56.5    7.8   109   23.6 
2025-05-10 00:00 UT   06 46 02.4   +02 28 21     6.761    6.248   55.7    7.7   110   23.6 
2025-05-11 00:00 UT   06 46 20.2   +02 26 25     6.779    6.254   54.9    7.6   110   23.6 
2025-05-12 00:00 UT   06 46 38.4   +02 24 27     6.797    6.260   54.1    7.5   111   23.6 
2025-05-13 00:00 UT   06 46 56.9   +02 22 27     6.816    6.265   53.3    7.4   111   23.6 
2025-05-14 00:00 UT   06 47 15.7   +02 20 26     6.834    6.271   52.6    7.4   112   23.6 
2025-05-15 00:00 UT   06 47 34.9   +02 18 22     6.851    6.277   51.8    7.3   112   23.7 
2025-05-16 00:00 UT   06 47 54.4   +02 16 17     6.869    6.283   51.0    7.2   113   23.7 

    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.