C/2012 S1 (ISON)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	28 Nov 2013	-6.3	0.014 AU	0.997 AU	16h18m	-21°36'	0.6°	42.7°	125°
Nearest approach	26 Dec 2013	6.7	1.001 AU	0.429 AU	16h28m	+52°41'	79.8°	75.3°	334°
Today	27 Nov 2025	27.5	29.467 AU	28.769 AU	07h33m	+37°02'	134.3°	1.4°	264°

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. (8.5 + 5 log[∆] + 8.0 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)                : 1.0000030
    q (Perihelion distance)         : 0.0142740
    i (Inclination)                 : 58.50260
    Ω (Longitude of ascending node) : 297.00650
    ω (Argument of perihelion)      : 345.13100
    L (Longitude of perihelion)     : 289.10921
    B (Latitude of perihelion)      : -12.63868
    T (Time of perihelion passage)  : 2456624.72160

    Epoch                           : 2025 Nov 27
    Reference                       : MPEC 2025-W75

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-11-26 00:00 UT   07 33 21.9   +37 01 35    28.782   29.459  132.6    1.4   265   27.5 
2025-11-27 00:00 UT   07 33 14.8   +37 02 12    28.774   29.463  133.5    1.4   264   27.5 
2025-11-27 19:13 UT   07 33 09.0   +37 02 41    28.769   29.467  134.3    1.4   264   27.5 
2025-11-28 00:00 UT   07 33 07.5   +37 02 48    28.767   29.468  134.5    1.4   264   27.5 
2025-11-29 00:00 UT   07 33 00.2   +37 03 24    28.760   29.472  135.5    1.3   263   27.5 
2025-11-30 00:00 UT   07 32 52.7   +37 03 60    28.754   29.477  136.4    1.3   263   27.5 
2025-12-01 00:00 UT   07 32 45.1   +37 04 35    28.747   29.481  137.4    1.3   262   27.5 
2025-12-02 00:00 UT   07 32 37.3   +37 05 11    28.741   29.486  138.3    1.3   262   27.5 
2025-12-03 00:00 UT   07 32 29.5   +37 05 46    28.735   29.490  139.3    1.2   261   27.5 
2025-12-04 00:00 UT   07 32 21.5   +37 06 21    28.730   29.495  140.3    1.2   260   27.5 
2025-12-05 00:00 UT   07 32 13.3   +37 06 55    28.724   29.499  141.2    1.2   260   27.5 
2025-12-06 00:00 UT   07 32 05.1   +37 07 30    28.719   29.504  142.1    1.2   259   27.5 
2025-12-07 00:00 UT   07 31 56.8   +37 08 04    28.714   29.508  143.1    1.1   258   27.6 

    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.