C/2021 K2 (MASTER)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	13 Jul 2021	18.7	5.481 AU	4.562 AU	19h28m	-49°41'	152.1°	5.0°	1°
Perihelion	9 Sep 2021	18.9	5.465 AU	5.075 AU	18h25m	-41°01'	107.6°	10.1°	82°
Today	13 Apr 2025	23.3	10.472 AU	10.280 AU	17h54m	+47°24'	98.3°	5.4°	247°

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/2021 K2 (MASTER) are:

            e (Eccentricity)                : 1.0005440
            q (Perihelion distance)         : 5.4646200
            i (Inclination)                 : 100.87070
            Ω (Longitude of ascending node) : 282.33590
            ω (Argument of perihelion)      : 343.28920
            L (Longitude of perihelion)     : 285.57650
            B (Latitude of perihelion)      : -16.40237
            T (Time of perihelion passage)  : 2459466.82270

            Epoch                           : 2025 Apr 12
            Reference                       : MPEC 2022-O01

            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 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. (8.00 + 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
2025-04-13 00:00 UT   17 54 41.6   +47 22 16    10.280   10.471   98.2    5.4   247   23.3 
2025-04-13 07:15 UT   17 54 36.4   +47 24 17    10.280   10.472   98.3    5.4   247   23.3 
2025-04-14 00:00 UT   17 54 24.1   +47 28 55    10.280   10.476   98.5    5.4   246   23.3 
2025-04-15 00:00 UT   17 54 05.9   +47 35 31    10.281   10.481   98.8    5.4   245   23.3 
2025-04-16 00:00 UT   17 53 47.2   +47 42 05    10.281   10.486   99.1    5.4   244   23.3 
2025-04-17 00:00 UT   17 53 27.8   +47 48 35    10.281   10.491   99.3    5.4   243   23.3 
2025-04-18 00:00 UT   17 53 07.9   +47 55 03    10.282   10.497   99.6    5.4   242   23.3 
2025-04-19 00:00 UT   17 52 47.4   +48 01 28    10.282   10.502   99.9    5.4   241   23.3 
2025-04-20 00:00 UT   17 52 26.3   +48 07 50    10.283   10.507  100.1    5.4   240   23.3 
2025-04-21 00:00 UT   17 52 04.6   +48 14 08    10.284   10.512  100.4    5.4   239   23.3 
2025-04-22 00:00 UT   17 51 42.3   +48 20 24    10.285   10.517  100.7    5.4   238   23.3 
2025-04-23 00:00 UT   17 51 19.4   +48 26 36    10.286   10.523  100.9    5.4   237   23.3 

    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.