C/2023 P1 (Nishimura)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	12 Sep 2023	3.4	0.289 AU	0.839 AU	11h10m	+18°59'	14.7°	117.7°	352°
Perihelion	17 Sep 2023	2.8	0.224 AU	0.926 AU	12h23m	+07°30'	12.4°	104.3°	66°
Today	28 Sep 2026	23.0	11.304 AU	11.829 AU	08h50m	-28°13'	56.2°	4.2°	252°

Please be aware that cometary behaviour is difficult to predict by nature. Predictions on this page are based on standard models and the latest observations available to me, and will gradually improve with time. The ability of comets to either disappoint or pleasantly surprise us, is one of many things that make them so interesting.

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.)

Light curve

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations from COBS. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 8.7 + 5 log[∆] + 8.5 log[r]). An additional green curve is displayed when an increase in apparent brightness is expected due to forward scattering of sunlight, which occurs when a dust-rich comet is located between the Earth and the Sun. (See Marcus 2007)

Charts

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.

Orbital elements

The orbital elements of C/2023 P1 (Nishimura) are:

    e (Eccentricity)                : 0.9959840
    q (Perihelion distance)         : 0.2236050
    i (Inclination)                 : 132.49010
    Ω (Longitude of ascending node) : 66.73480
    ω (Argument of perihelion)      : 116.14520
    L (Longitude of perihelion)     : 120.72808
    B (Latitude of perihelion)      : 41.44831
    T (Time of perihelion passage)  : 2460204.88970
    P (Orbital period in years)     : 415.46

    Epoch                           : 2026 Sep 28
    Reference                       : MPC194185

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-09-27 00:00 UT   08 49 56.8   -28 07 45    11.831   11.291   55.3    4.2   250   23.0 
2026-09-28 00:00 UT   08 50 07.5   -28 11 07    11.830   11.298   55.8    4.2   251   23.0 
2026-09-28 18:47 UT   08 50 15.7   -28 13 45    11.829   11.304   56.2    4.2   252   23.0 
2026-09-29 00:00 UT   08 50 18.0   -28 14 30    11.829   11.305   56.3    4.2   252   23.0 
2026-09-30 00:00 UT   08 50 28.2   -28 17 54    11.828   11.312   56.9    4.3   253   23.0 
2026-10-01 00:00 UT   08 50 38.0   -28 21 20    11.826   11.319   57.4    4.3   254   23.0 
2026-10-02 00:00 UT   08 50 47.6   -28 24 47    11.824   11.325   58.0    4.3   255   23.0 
2026-10-03 00:00 UT   08 50 56.9   -28 28 15    11.822   11.332   58.5    4.3   256   23.0 
2026-10-04 00:00 UT   08 51 05.8   -28 31 44    11.820   11.339   59.1    4.3   257   23.0 
2026-10-05 00:00 UT   08 51 14.5   -28 35 14    11.818   11.346   59.6    4.4   258   23.0 
2026-10-06 00:00 UT   08 51 22.8   -28 38 46    11.816   11.352   60.2    4.4   258   23.0 
2026-10-07 00:00 UT   08 51 30.8   -28 42 18    11.813   11.359   60.8    4.4   259   23.0 
2026-10-08 00:00 UT   08 51 38.5   -28 45 51    11.811   11.366   61.3    4.4   260   23.0 

    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.