C/2017 E2 (Tsuchinshan)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	22 Oct 2015	18.3	3.156 AU	2.319 AU	23h33m	+35°44'	141.1°	11.4°	121°
Perihelion	16 May 2016	17.3	2.325 AU	2.666 AU	01h51m	+77°35'	59.7°	22.0°	331°
Today	26 Mar 2026	31.1	20.373 AU	19.923 AU	11h00m	-65°06'	115.5°	2.5°	23°

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. (11.5 + 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/2017 E2 (Tsuchinshan) are:

    e (Eccentricity)                : 0.8920530
    q (Perihelion distance)         : 2.3251060
    i (Inclination)                 : 79.01140
    Ω (Longitude of ascending node) : 11.47650
    ω (Argument of perihelion)      : 89.19000
    L (Longitude of perihelion)     : 97.23455
    B (Latitude of perihelion)      : 78.98195
    T (Time of perihelion passage)  : 2457525.45070
    P (Orbital period in years)     : 99.97

    Epoch                           : 2026 Mar 16
    Reference                       : MPEC 2026-E44

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-03-25 00:00 UT   11 00 56.2   -65 08 08    19.923   20.366  115.1    2.5    20   31.1 
2026-03-26 00:00 UT   11 00 30.3   -65 07 05    19.923   20.370  115.3    2.5    22   31.1 
2026-03-26 20:45 UT   11 00 08.1   -65 06 08    19.923   20.373  115.5    2.5    23   31.1 
2026-03-27 00:00 UT   11 00 04.6   -65 05 59    19.923   20.373  115.6    2.5    23   31.1 
2026-03-28 00:00 UT   10 59 39.1   -65 04 50    19.922   20.377  115.8    2.5    24   31.1 
2026-03-29 00:00 UT   10 59 13.8   -65 03 39    19.922   20.380  116.0    2.5    25   31.1 
2026-03-30 00:00 UT   10 58 48.7   -65 02 25    19.922   20.384  116.2    2.5    26   31.1 
2026-03-31 00:00 UT   10 58 23.9   -65 01 08    19.922   20.387  116.5    2.5    28   31.1 
2026-04-01 00:00 UT   10 57 59.3   -64 59 48    19.923   20.391  116.6    2.5    29   31.1 
2026-04-02 00:00 UT   10 57 35.0   -64 58 26    19.923   20.394  116.8    2.5    30   31.1 
2026-04-03 00:00 UT   10 57 10.9   -64 57 01    19.924   20.398  117.0    2.5    31   31.1 
2026-04-04 00:00 UT   10 56 47.0   -64 55 34    19.925   20.401  117.2    2.5    32   31.1 
2026-04-05 00:00 UT   10 56 23.5   -64 54 04    19.926   20.405  117.3    2.5    34   31.1 

    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.