C/2018 A3 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	8 Jan 2019	15.4	3.299 AU	2.627 AU	09h08m	+74°29'	125.7°	14.0°	212°
Nearest approach	9 Jan 2019	15.4	3.299 AU	2.627 AU	09h03m	+74°41'	125.7°	14.0°	210°
Today	28 Aug 2026	27.2	18.904 AU	17.992 AU	23h44m	-28°41'	153.8°	1.4°	313°

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)                : 0.9906870
    q (Perihelion distance)         : 3.2988290
    i (Inclination)                 : 139.65230
    Ω (Longitude of ascending node) : 194.40640
    ω (Argument of perihelion)      : 86.60850
    L (Longitude of perihelion)     : 108.85269
    B (Latitude of perihelion)      : 40.26251
    T (Time of perihelion passage)  : 2458492.10440
    P (Orbital period in years)     : 6666.61

    Epoch                           : 2026 May 29
    Reference                       : MPC194154

    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
2026-08-27 00:00 UT   23 44 55.6   -28 38 27    17.988   18.895  153.1    1.4   309   27.2 
2026-08-28 00:00 UT   23 44 41.8   -28 40 26    17.990   18.900  153.5    1.4   311   27.2 
2026-08-28 17:18 UT   23 44 31.8   -28 41 51    17.992   18.904  153.8    1.4   313   27.2 
2026-08-29 00:00 UT   23 44 28.0   -28 42 23    17.993   18.905  153.9    1.3   313   27.2 
2026-08-30 00:00 UT   23 44 14.0   -28 44 20    17.996   18.910  154.2    1.3   316   27.2 
2026-08-31 00:00 UT   23 43 60.0   -28 46 15    17.999   18.915  154.4    1.3   318   27.2 
2026-09-01 00:00 UT   23 43 45.9   -28 48 09    18.003   18.920  154.7    1.3   320   27.2 
2026-09-02 00:00 UT   23 43 31.7   -28 50 02    18.006   18.925  154.9    1.3   323   27.2 
2026-09-03 00:00 UT   23 43 17.4   -28 51 54    18.010   18.930  155.0    1.3   325   27.2 
2026-09-04 00:00 UT   23 43 03.1   -28 53 44    18.015   18.935  155.2    1.3   327   27.2 
2026-09-05 00:00 UT   23 42 48.7   -28 55 33    18.019   18.940  155.3    1.3   330   27.2 
2026-09-06 00:00 UT   23 42 34.3   -28 57 21    18.024   18.945  155.3    1.3   332   27.2 
2026-09-07 00:00 UT   23 42 19.8   -28 59 07    18.030   18.950  155.3    1.3   335   27.2 

    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.