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	13 Aug 2026	27.2	18.828 AU	17.982 AU	23h47m	-28°10'	145.7°	1.7°	286°

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
2026-08-12 00:00 UT   23 48 08.9   -28 06 59    17.985   18.820  144.6    1.8   284   27.2 
2026-08-13 00:00 UT   23 47 56.9   -28 09 10    17.983   18.825  145.3    1.8   285   27.2 
2026-08-13 14:04 UT   23 47 49.8   -28 10 27    17.982   18.828  145.7    1.7   286   27.2 
2026-08-14 00:00 UT   23 47 44.8   -28 11 20    17.982   18.830  146.0    1.7   287   27.2 
2026-08-15 00:00 UT   23 47 32.5   -28 13 30    17.981   18.835  146.6    1.7   288   27.2 
2026-08-16 00:00 UT   23 47 20.1   -28 15 39    17.980   18.840  147.3    1.7   289   27.2 
2026-08-17 00:00 UT   23 47 07.6   -28 17 48    17.979   18.845  147.9    1.6   291   27.2 
2026-08-18 00:00 UT   23 46 54.9   -28 19 55    17.979   18.850  148.5    1.6   292   27.2 
2026-08-19 00:00 UT   23 46 42.1   -28 22 02    17.979   18.855  149.1    1.6   294   27.2 
2026-08-20 00:00 UT   23 46 29.2   -28 24 09    17.979   18.860  149.7    1.5   296   27.2 
2026-08-21 00:00 UT   23 46 16.2   -28 26 14    17.979   18.865  150.3    1.5   297   27.2 
2026-08-22 00:00 UT   23 46 03.0   -28 28 18    17.980   18.870  150.8    1.5   299   27.2 
2026-08-23 00:00 UT   23 45 49.8   -28 30 22    17.981   18.875  151.3    1.5   301   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.