C/2018 A3 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	8 Jan 2019	15.4	3.298 AU	2.626 AU	09h08m	+74°29'	125.7°	14.0°	212°
Nearest approach	9 Jan 2019	15.4	3.298 AU	2.626 AU	09h03m	+74°41'	125.7°	14.0°	210°
Today	2 May 2026	27.2	18.307 AU	18.835 AU	23h51m	-25°18'	57.0°	2.6°	229°

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)                : 0.9906260
    q (Perihelion distance)         : 3.2979310
    i (Inclination)                 : 139.64260
    Ω (Longitude of ascending node) : 194.39520
    ω (Argument of perihelion)      : 86.58880
    L (Longitude of perihelion)     : 108.86791
    B (Latitude of perihelion)      : 40.27119
    T (Time of perihelion passage)  : 2458492.03510
    P (Orbital period in years)     : 6598.95

    Epoch                           : 2026 Mar 16
    Reference                       : MPEC 2026-E44

    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
2026-05-01 00:00 UT   23 50 51.3   -25 18 30    18.843   18.301   56.1    2.6   229   27.2 
2026-05-02 00:00 UT   23 50 59.6   -25 18 57    18.836   18.306   56.9    2.6   229   27.2 
2026-05-02 02:57 UT   23 51 00.6   -25 18 60    18.835   18.307   57.0    2.6   229   27.2 
2026-05-03 00:00 UT   23 51 07.7   -25 19 25    18.828   18.311   57.8    2.7   230   27.2 
2026-05-04 00:00 UT   23 51 15.6   -25 19 55    18.820   18.316   58.6    2.7   230   27.2 
2026-05-05 00:00 UT   23 51 23.5   -25 20 27    18.812   18.321   59.5    2.7   231   27.2 
2026-05-06 00:00 UT   23 51 31.1   -25 21 00    18.804   18.326   60.3    2.7   231   27.2 
2026-05-07 00:00 UT   23 51 38.6   -25 21 35    18.796   18.331   61.2    2.8   232   27.2 
2026-05-08 00:00 UT   23 51 46.0   -25 22 12    18.787   18.337   62.1    2.8   232   27.2 
2026-05-09 00:00 UT   23 51 53.2   -25 22 51    18.779   18.342   62.9    2.8   232   27.2 
2026-05-10 00:00 UT   23 52 00.3   -25 23 32    18.770   18.347   63.8    2.8   233   27.2 
2026-05-11 00:00 UT   23 52 07.2   -25 24 14    18.761   18.352   64.6    2.9   233   27.2 
2026-05-12 00:00 UT   23 52 13.9   -25 24 58    18.752   18.357   65.5    2.9   234   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.