C/2023 H5 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	22 Feb 2025	16.3	4.441 AU	3.739 AU	12h12m	+55°03'	130.1°	9.8°	217°
Today	12 Mar 2025	16.3	4.408 AU	3.787 AU	11h52m	+60°11'	123.0°	10.9°	187°
Perihelion	30 Jun 2025	16.7	4.313 AU	4.760 AU	10h54m	+64°16'	58.3°	11.6°	77°

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/2023 H5 (Lemmon) are:

            e (Eccentricity)                : 1.0004210
            q (Perihelion distance)         : 4.3126370
            i (Inclination)                 : 97.85570
            Ω (Longitude of ascending node) : 159.47880
            ω (Argument of perihelion)      : 60.09260
            L (Longitude of perihelion)     : 146.11205
            B (Latitude of perihelion)      : 59.17065
            T (Time of perihelion passage)  : 2460856.73420

            Epoch                           : 2025 Mar 10
            Reference                       : MPEC 2025-EB9

            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 (7.00 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 6.98 + 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
2025-03-12 00:00 UT   11 52 29.1   +60 08 47     3.786    4.408  123.1   10.9   187   16.3 
2025-03-12 04:37 UT   11 52 13.5   +60 11 35     3.787    4.408  123.0   10.9   187   16.3 
2025-03-13 00:00 UT   11 51 07.3   +60 23 12     3.791    4.406  122.5   11.0   186   16.3 
2025-03-14 00:00 UT   11 49 44.4   +60 37 17     3.797    4.405  122.0   11.0   184   16.3 
2025-03-15 00:00 UT   11 48 20.4   +60 51 04     3.802    4.403  121.4   11.1   183   16.3 
2025-03-16 00:00 UT   11 46 55.4   +61 04 30     3.808    4.401  120.8   11.2   181   16.3 
2025-03-17 00:00 UT   11 45 29.4   +61 17 38     3.815    4.400  120.2   11.3   180   16.3 
2025-03-18 00:00 UT   11 44 02.5   +61 30 25     3.821    4.398  119.6   11.4   178   16.3 
2025-03-19 00:00 UT   11 42 34.7   +61 42 53     3.828    4.396  118.9   11.4   177   16.3 
2025-03-20 00:00 UT   11 41 06.2   +61 55 01     3.834    4.395  118.3   11.5   175   16.3 
2025-03-21 00:00 UT   11 39 37.1   +62 06 49     3.842    4.393  117.6   11.6   174   16.3 
2025-03-22 00:00 UT   11 38 07.3   +62 18 16     3.849    4.392  117.0   11.7   173   16.3 

    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.