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°47'	141.0°	11.4°	121°
Perihelion	16 May 2016	17.3	2.326 AU	2.666 AU	01h51m	+77°34'	59.7°	22.0°	331°
Today	28 Jul 2026	31.3	20.800 AU	20.863 AU	10h52m	-61°00'	85.0°	2.8°	146°

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)                : 0.8920280
    q (Perihelion distance)         : 2.3257550
    i (Inclination)                 : 78.99950
    Ω (Longitude of ascending node) : 11.45460
    ω (Argument of perihelion)      : 89.19900
    L (Longitude of perihelion)     : 97.26409
    B (Latitude of perihelion)      : 78.97073
    T (Time of perihelion passage)  : 2457525.34250
    P (Orbital period in years)     : 99.97

    Epoch                           : 2026 May 29
    Reference                       : MPC194150

    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
2026-07-27 00:00 UT   10 52 04.3   -61 01 44    20.846   20.795   85.7    2.8   145   31.3 
2026-07-28 00:00 UT   10 52 20.3   -61 00 45    20.858   20.798   85.2    2.8   146   31.3 
2026-07-28 10:52 UT   10 52 27.5   -61 00 19    20.863   20.800   85.0    2.8   146   31.3 
2026-07-29 00:00 UT   10 52 36.3   -60 59 48    20.870   20.802   84.7    2.8   147   31.3 
2026-07-30 00:00 UT   10 52 52.6   -60 58 54    20.882   20.805   84.3    2.8   148   31.3 
2026-07-31 00:00 UT   10 53 09.1   -60 58 02    20.894   20.809   83.8    2.8   148   31.3 
2026-08-01 00:00 UT   10 53 25.7   -60 57 12    20.906   20.812   83.3    2.8   149   31.3 
2026-08-02 00:00 UT   10 53 42.5   -60 56 24    20.917   20.816   82.8    2.8   150   31.3 
2026-08-03 00:00 UT   10 53 59.4   -60 55 39    20.929   20.819   82.4    2.8   151   31.3 
2026-08-04 00:00 UT   10 54 16.5   -60 54 57    20.941   20.822   81.9    2.8   151   31.3 
2026-08-05 00:00 UT   10 54 33.7   -60 54 16    20.953   20.826   81.4    2.8   152   31.3 
2026-08-06 00:00 UT   10 54 51.2   -60 53 38    20.965   20.829   80.9    2.8   153   31.3 
2026-08-07 00:00 UT   10 55 08.7   -60 53 03    20.976   20.833   80.5    2.8   154   31.3 

    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.