C/2021 O1 (Nishimura)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	6 Aug 2021	9.4	0.799 AU	1.689 AU	08h11m	+30°59'	18.8°	24.2°	316°
Perihelion	14 Aug 2021	9.3	0.783 AU	1.702 AU	09h06m	+28°58'	16.3°	21.3°	333°
Today	8 Jan 2025	25.6	11.978 AU	12.832 AU	17h33m	-41°03'	28.7°	2.3°	237°

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 O1 (Nishimura) are:

            e (Eccentricity)                : 0.9997910
            q (Perihelion distance)         : 0.7828550
            i (Inclination)                 : 27.58400
            Ω (Longitude of ascending node) : 41.57160
            ω (Argument of perihelion)      : 74.39760
            L (Longitude of perihelion)     : 114.08392
            B (Latitude of perihelion)      : 26.48643
            T (Time of perihelion passage)  : 2459441.08020
            P (Orbital period in years)     : 229246.42

            Epoch                           : 2025 Jan 06
            Reference                       : MPEC 2022-A21

            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 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 (10.50 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 9.23 + 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
2025-01-08 00:00 UT   17 33 56.1   -41 03 07    12.832   11.978   28.6    2.2   237   25.6 
2025-01-08 03:15 UT   17 33 59.4   -41 03 15    12.832   11.978   28.7    2.3   237   25.6 
2025-01-09 00:00 UT   17 34 20.8   -41 04 06    12.832   11.984   29.3    2.3   238   25.6 
2025-01-10 00:00 UT   17 34 45.4   -41 05 07    12.832   11.991   30.0    2.4   239   25.6 
2025-01-11 00:00 UT   17 35 09.7   -41 06 08    12.832   11.998   30.8    2.4   240   25.6 
2025-01-12 00:00 UT   17 35 33.9   -41 07 10    12.831   12.005   31.6    2.5   241   25.6 
2025-01-13 00:00 UT   17 35 58.0   -41 08 12    12.830   12.012   32.3    2.5   242   25.6 
2025-01-14 00:00 UT   17 36 21.8   -41 09 16    12.830   12.018   33.1    2.6   243   25.6 
2025-01-15 00:00 UT   17 36 45.4   -41 10 21    12.828   12.025   33.9    2.6   244   25.6 
2025-01-16 00:00 UT   17 37 08.8   -41 11 27    12.827   12.032   34.7    2.7   245   25.6 
2025-01-17 00:00 UT   17 37 32.1   -41 12 33    12.825   12.039   35.5    2.7   245   25.6 
2025-01-18 00:00 UT   17 37 55.1   -41 13 41    12.824   12.045   36.3    2.8   246   25.6 

    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.