C/2018 A3 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	8 Jan 2019	15.4	3.296 AU	2.624 AU	09h09m	+74°29'	125.7°	14.0°	213°
Nearest approach	9 Jan 2019	15.4	3.296 AU	2.624 AU	09h04m	+74°42'	125.7°	14.0°	210°
Today	2 Jan 2026	26.9	17.698 AU	18.130 AU	23h31m	-26°54'	62.6°	2.8°	77°

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. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 8.1 + 5 log[∆] + 10.1 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/2018 A3 (ATLAS) are:

    e (Eccentricity)                : 0.9905380
    q (Perihelion distance)         : 3.2961650
    i (Inclination)                 : 139.62740
    Ω (Longitude of ascending node) : 194.37810
    ω (Argument of perihelion)      : 86.55610
    L (Longitude of perihelion)     : 108.89463
    B (Latitude of perihelion)      : 40.28468
    T (Time of perihelion passage)  : 2458492.02450
    P (Orbital period in years)     : 6501.88

    Epoch                           : 2025 Nov 12
    Reference                       : MPEC 2021-P47

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-01-01 00:00 UT   23 31 42.7   -26 56 39    18.092   17.688   64.3    2.9    76   26.9 
2026-01-02 00:00 UT   23 31 46.1   -26 55 23    18.111   17.694   63.4    2.8    76   26.9 
2026-01-02 22:49 UT   23 31 49.6   -26 54 10    18.130   17.698   62.6    2.8    77   26.9 
2026-01-03 00:00 UT   23 31 49.8   -26 54 07    18.131   17.699   62.5    2.8    77   26.9 
2026-01-04 00:00 UT   23 31 53.7   -26 52 50    18.150   17.704   61.6    2.8    77   26.9 
2026-01-05 00:00 UT   23 31 57.7   -26 51 32    18.169   17.709   60.7    2.8    78   26.9 
2026-01-06 00:00 UT   23 32 02.0   -26 50 14    18.188   17.714   59.8    2.7    78   26.9 
2026-01-07 00:00 UT   23 32 06.5   -26 48 56    18.207   17.719   58.9    2.7    79   26.9 
2026-01-08 00:00 UT   23 32 11.2   -26 47 37    18.225   17.724   58.0    2.7    79   27.0 
2026-01-09 00:00 UT   23 32 16.2   -26 46 18    18.244   17.730   57.1    2.7    80   27.0 
2026-01-10 00:00 UT   23 32 21.3   -26 44 59    18.262   17.735   56.2    2.6    80   27.0 
2026-01-11 00:00 UT   23 32 26.6   -26 43 39    18.280   17.740   55.3    2.6    81   27.0 
2026-01-12 00:00 UT   23 32 32.1   -26 42 19    18.298   17.745   54.4    2.6    81   27.0 

    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.