C/2017 A3 (Elenin)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	24 Jan 2017	18.0	3.841 AU	3.412 AU	06h18m	-46°04'	108.6°	14.1°	32°
Perihelion	31 Jan 2017	18.0	3.840 AU	3.417 AU	06h10m	-43°51'	108.2°	14.1°	41°
Today	22 Jun 2025	28.6	18.691 AU	18.983 AU	21h21m	+82°06'	71.8°	3.0°	227°

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.)

The orbital elements of C/2017 A3 (Elenin) are:

            e (Eccentricity)                : 0.9113940
            q (Perihelion distance)         : 3.8404320
            i (Inclination)                 : 98.50290
            Ω (Longitude of ascending node) : 97.85120
            ω (Argument of perihelion)      : 303.92640
            L (Longitude of perihelion)     : 110.24874
            B (Latitude of perihelion)      : -55.14840
            T (Time of perihelion passage)  : 2457784.51680
            P (Orbital period in years)     : 285.35

            Epoch                           : 2022 Mar 31
            Reference                       : MPC108594

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

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. 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. (9.50 + 5 log[∆] + 10.00 log[r]).

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-06-22 00:00 UT   21 21 47.6   +82 05 32    18.982   18.690   71.8    3.0   228   28.6 
2025-06-22 06:35 UT   21 21 29.4   +82 06 04    18.983   18.691   71.8    3.0   227   28.6 
2025-06-23 00:00 UT   21 20 40.4   +82 07 28    18.984   18.694   71.9    3.0   226   28.6 
2025-06-24 00:00 UT   21 19 31.7   +82 09 22    18.987   18.698   72.0    3.0   225   28.6 
2025-06-25 00:00 UT   21 18 21.4   +82 11 12    18.989   18.703   72.1    3.0   224   28.6 
2025-06-26 00:00 UT   21 17 09.5   +82 13 00    18.991   18.707   72.3    3.0   223   28.6 
2025-06-27 00:00 UT   21 15 56.1   +82 14 45    18.993   18.711   72.4    3.0   221   28.6 
2025-06-28 00:00 UT   21 14 41.3   +82 16 27    18.995   18.716   72.5    3.0   220   28.6 
2025-06-29 00:00 UT   21 13 24.9   +82 18 05    18.997   18.720   72.7    3.0   219   28.6 
2025-06-30 00:00 UT   21 12 07.1   +82 19 41    18.999   18.724   72.8    3.0   217   28.6 
2025-07-01 00:00 UT   21 10 47.9   +82 21 13    19.000   18.729   73.0    3.0   216   28.6 
2025-07-02 00:00 UT   21 09 27.3   +82 22 41    19.002   18.733   73.1    3.0   215   28.6 

    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.