421P/McNaught
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	21 May 2020	20.2	2.950 AU	2.037 AU	13h57m	-07°51'	148.8°	10.2°	117°
Perihelion	24 Jan 2021	18.3	1.652 AU	2.617 AU	21h01m	-23°28'	9.2°	5.5°	116°
Today	22 Dec 2024	27.2	7.886 AU	7.048 AU	08h31m	+29°20'	146.4°	4.0°	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 421P/McNaught are:

            e (Eccentricity)                : 0.6744410
            q (Perihelion distance)         : 1.6524400
            i (Inclination)                 : 10.07570
            Ω (Longitude of ascending node) : 55.33130
            ω (Argument of perihelion)      : 259.88270
            L (Longitude of perihelion)     : 135.05887
            B (Latitude of perihelion)      : -9.91743
            T (Time of perihelion passage)  : 2459238.73640
            P (Orbital period in years)     : 11.44

            Epoch                           : 2024 Dec 21
            Reference                       : MPEC 2021-W31

            Classification(s):              : Ecliptic; Jupiter family
            Tisserand (Jupiter)             : 2.461
        

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. (14.00 + 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
2024-12-22 00:00 UT   08 31 53.0   +29 19 45     7.051    7.885  145.9    4.0   269   27.2 
2024-12-22 11:10 UT   08 31 42.1   +29 20 48     7.048    7.886  146.4    4.0   269   27.2 
2024-12-23 00:00 UT   08 31 29.4   +29 21 60     7.044    7.887  146.9    3.9   268   27.2 
2024-12-24 00:00 UT   08 31 05.4   +29 24 14     7.037    7.889  148.0    3.8   268   27.2 
2024-12-25 00:00 UT   08 30 41.0   +29 26 28     7.031    7.890  149.0    3.7   267   27.2 
2024-12-26 00:00 UT   08 30 16.1   +29 28 42     7.025    7.892  150.1    3.6   266   27.2 
2024-12-27 00:00 UT   08 29 50.9   +29 30 56     7.019    7.894  151.1    3.4   265   27.2 
2024-12-28 00:00 UT   08 29 25.2   +29 33 09     7.013    7.896  152.2    3.3   264   27.2 
2024-12-29 00:00 UT   08 28 59.2   +29 35 21     7.008    7.898  153.2    3.2   263   27.2 
2024-12-30 00:00 UT   08 28 32.8   +29 37 33     7.003    7.900  154.2    3.1   262   27.2 
2024-12-31 00:00 UT   08 28 06.0   +29 39 44     6.998    7.902  155.2    3.0   261   27.2 
2025-01-01 00:00 UT   08 27 38.9   +29 41 55     6.994    7.904  156.2    2.9   260   27.2 

    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.