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	1 Apr 2025	28.5	18.337 AU	18.523 AU	21h34m	+78°40'	77.7°	3.1°	311°

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
2025-04-01 00:00 UT   21 33 55.7   +78 38 48    18.517   18.334   77.9    3.1   312   28.5 
2025-04-01 16:18 UT   21 34 18.0   +78 40 12    18.523   18.337   77.7    3.1   311   28.5 
2025-04-02 00:00 UT   21 34 28.5   +78 40 52    18.526   18.339   77.6    3.1   311   28.5 
2025-04-03 00:00 UT   21 35 00.6   +78 42 59    18.535   18.343   77.4    3.0   310   28.5 
2025-04-04 00:00 UT   21 35 32.0   +78 45 07    18.543   18.347   77.2    3.0   309   28.5 
2025-04-05 00:00 UT   21 36 02.7   +78 47 17    18.552   18.352   76.9    3.0   309   28.5 
2025-04-06 00:00 UT   21 36 32.8   +78 49 28    18.560   18.356   76.7    3.0   308   28.5 
2025-04-07 00:00 UT   21 37 02.1   +78 51 41    18.568   18.360   76.5    3.0   307   28.5 
2025-04-08 00:00 UT   21 37 30.7   +78 53 56    18.577   18.365   76.2    3.0   306   28.5 
2025-04-09 00:00 UT   21 37 58.6   +78 56 12    18.585   18.369   76.0    3.0   305   28.5 
2025-04-10 00:00 UT   21 38 25.8   +78 58 30    18.593   18.373   75.8    3.0   304   28.5 
2025-04-11 00:00 UT   21 38 52.2   +79 00 50    18.601   18.378   75.6    3.0   303   28.5 

    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.