C/2012 S1 (ISON)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	1 Dec 2013	-9.3	0.013 AU	0.996 AU	16h32m	-22°08'	0.5°	39.8°	126°
Nearest approach	28 Dec 2013	7.6	0.986 AU	0.426 AU	16h59m	+51°55'	77.8°	77.2°	339°
Today	23 Oct 2025	31.8	30.822 AU	30.626 AU	07h34m	+36°56'	100.4°	1.8°	277°

This comet is a sungrazer. Although it may become very bright at perihelion, this will only be for a very short period very close to the sun.

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. 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. (9.5 + 5 log[∆] + 10.0 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/2012 S1 (ISON) are:

    e (Eccentricity)                : 1.0002330
    q (Perihelion distance)         : 0.0132770
    i (Inclination)                 : 63.89100
    Ω (Longitude of ascending node) : 295.10960
    ω (Argument of perihelion)      : 345.92900
    L (Longitude of perihelion)     : 288.81511
    B (Latitude of perihelion)      : -12.61010
    T (Time of perihelion passage)  : 2456628.07350

    Epoch                           : 2022 May 11
    Reference                       : MPEC 2022-H30

    Classification(s):              : Nearly isotropic; New (a > 10000 AU); Sungrazer

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-10-22 00:00 UT   07 34 54.1   +36 56 02    30.646   30.813   98.7    1.8   277   31.8 
2025-10-23 00:00 UT   07 34 52.7   +36 56 35    30.634   30.818   99.7    1.8   277   31.8 
2025-10-23 18:28 UT   07 34 51.5   +36 56 60    30.626   30.822  100.4    1.8   277   31.8 
2025-10-24 00:00 UT   07 34 51.2   +36 57 07    30.623   30.823  100.7    1.8   277   31.8 
2025-10-25 00:00 UT   07 34 49.4   +36 57 40    30.612   30.828  101.6    1.8   276   31.8 
2025-10-26 00:00 UT   07 34 47.5   +36 58 14    30.600   30.833  102.6    1.8   276   31.8 
2025-10-27 00:00 UT   07 34 45.5   +36 58 47    30.589   30.838  103.6    1.8   276   31.8 
2025-10-28 00:00 UT   07 34 43.3   +36 59 21    30.578   30.843  104.5    1.8   276   31.8 
2025-10-29 00:00 UT   07 34 40.9   +36 59 54    30.567   30.848  105.5    1.8   275   31.8 
2025-10-30 00:00 UT   07 34 38.3   +37 00 28    30.556   30.853  106.5    1.8   275   31.8 
2025-10-31 00:00 UT   07 34 35.6   +37 01 03    30.545   30.858  107.4    1.8   275   31.8 
2025-11-01 00:00 UT   07 34 32.7   +37 01 37    30.534   30.863  108.4    1.7   274   31.8 
2025-11-02 00:00 UT   07 34 29.7   +37 02 12    30.524   30.868  109.4    1.7   274   31.8 

    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.