C/2012 S1 (ISON)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	27 Nov 2013	-2.3	0.014 AU	0.997 AU	16h15m	-21°30'	0.6°	43.3°	125°
Nearest approach	25 Dec 2013	6.7	1.005 AU	0.431 AU	16h20m	+52°49'	80.3°	74.7°	333°
Today	1 Apr 2026	27.7	30.020 AU	29.929 AU	07h16m	+37°11'	94.3°	1.9°	99°

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)                : 1.0000020
    q (Perihelion distance)         : 0.0142140
    i (Inclination)                 : 58.39240
    Ω (Longitude of ascending node) : 297.04700
    ω (Argument of perihelion)      : 345.10390
    L (Longitude of perihelion)     : 289.11034
    B (Latitude of perihelion)      : -12.64637
    T (Time of perihelion passage)  : 2456624.06540

    Epoch                           : 2026 Mar 16
    Reference                       : MPC191584

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-03-31 00:00 UT   07 17 00.2   +37 11 53    29.899   30.014   95.6    1.9    99   27.7 
2026-04-01 00:00 UT   07 16 58.9   +37 11 24    29.920   30.019   94.7    1.9    99   27.7 
2026-04-01 10:21 UT   07 16 58.3   +37 11 12    29.929   30.020   94.3    1.9    99   27.7 
2026-04-02 00:00 UT   07 16 57.7   +37 10 55    29.941   30.023   93.7    1.9    99   27.7 
2026-04-03 00:00 UT   07 16 56.7   +37 10 26    29.962   30.027   92.8    1.9    99   27.7 
2026-04-04 00:00 UT   07 16 55.9   +37 09 56    29.983   30.032   91.8    1.9    98   27.7 
2026-04-05 00:00 UT   07 16 55.3   +37 09 26    30.004   30.036   90.9    1.9    98   27.7 
2026-04-06 00:00 UT   07 16 54.8   +37 08 56    30.025   30.041   89.9    1.9    98   27.7 
2026-04-07 00:00 UT   07 16 54.5   +37 08 26    30.046   30.045   89.0    1.9    98   27.7 
2026-04-08 00:00 UT   07 16 54.4   +37 07 55    30.067   30.050   88.0    1.9    97   27.7 
2026-04-09 00:00 UT   07 16 54.4   +37 07 24    30.088   30.054   87.1    1.9    97   27.7 
2026-04-10 00:00 UT   07 16 54.6   +37 06 53    30.109   30.059   86.1    1.9    97   27.7 
2026-04-11 00:00 UT   07 16 55.0   +37 06 22    30.130   30.063   85.2    1.9    97   27.7 

    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.