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	3 Jul 2025	28.6	18.738 AU	19.004 AU	21h07m	+82°24'	73.3°	3.0°	213°

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
2025-07-03 00:00 UT   21 08 05.4   +82 24 07    19.004   18.737   73.3    3.0   214   28.6 
2025-07-03 05:12 UT   21 07 47.4   +82 24 25    19.004   18.738   73.3    3.0   213   28.6 
2025-07-04 00:00 UT   21 06 42.1   +82 25 29    19.005   18.742   73.5    3.0   212   28.6 
2025-07-05 00:00 UT   21 05 17.6   +82 26 47    19.007   18.746   73.6    3.0   211   28.6 
2025-07-06 00:00 UT   21 03 51.8   +82 28 01    19.008   18.750   73.8    3.0   210   28.6 
2025-07-07 00:00 UT   21 02 24.9   +82 29 13    19.009   18.754   74.0    3.0   208   28.6 
2025-07-08 00:00 UT   21 00 56.8   +82 30 20    19.011   18.759   74.1    3.0   207   28.6 
2025-07-09 00:00 UT   20 59 27.6   +82 31 23    19.012   18.763   74.3    3.0   206   28.6 
2025-07-10 00:00 UT   20 57 57.4   +82 32 23    19.013   18.767   74.5    3.0   204   28.6 
2025-07-11 00:00 UT   20 56 26.1   +82 33 19    19.014   18.772   74.7    3.0   203   28.6 
2025-07-12 00:00 UT   20 54 53.9   +82 34 11    19.015   18.776   74.9    3.0   202   28.6 
2025-07-13 00:00 UT   20 53 20.8   +82 34 59    19.016   18.780   75.1    3.0   200   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.