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	5 Mar 2026	27.1	18.011 AU	18.930 AU	23h40m	-25°37'	21.5°	1.2°	153°

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
2026-03-04 00:00 UT   23 40 25.3   -25 38 13    18.924   18.006   21.6    1.2   150   27.1 
2026-03-05 00:00 UT   23 40 36.9   -25 37 14    18.929   18.011   21.5    1.2   152   27.1 
2026-03-05 01:02 UT   23 40 37.4   -25 37 11    18.930   18.011   21.5    1.2   153   27.1 
2026-03-06 00:00 UT   23 40 48.5   -25 36 16    18.935   18.016   21.5    1.2   155   27.1 
2026-03-07 00:00 UT   23 41 00.2   -25 35 19    18.940   18.021   21.5    1.2   158   27.1 
2026-03-08 00:00 UT   23 41 11.9   -25 34 23    18.945   18.026   21.6    1.2   160   27.1 
2026-03-09 00:00 UT   23 41 23.6   -25 33 29    18.949   18.031   21.7    1.2   163   27.1 
2026-03-10 00:00 UT   23 41 35.3   -25 32 35    18.954   18.037   21.8    1.2   165   27.1 
2026-03-11 00:00 UT   23 41 47.0   -25 31 43    18.958   18.042   22.0    1.2   168   27.1 
2026-03-12 00:00 UT   23 41 58.8   -25 30 52    18.962   18.047   22.3    1.2   170   27.1 
2026-03-13 00:00 UT   23 42 10.5   -25 30 02    18.965   18.052   22.5    1.2   173   27.1 
2026-03-14 00:00 UT   23 42 22.3   -25 29 13    18.969   18.057   22.8    1.2   175   27.1 
2026-03-15 00:00 UT   23 42 34.0   -25 28 25    18.972   18.062   23.1    1.2   177   27.1 

    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.