C/2018 A3 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	8 Jan 2019	15.4	3.294 AU	2.622 AU	09h09m	+74°31'	125.6°	14.0°	212°
Nearest approach	9 Jan 2019	15.4	3.294 AU	2.622 AU	09h04m	+74°43'	125.6°	14.0°	210°
Today	3 Jul 2025	26.5	16.744 AU	16.380 AU	00h01m	-23°56'	109.3°	3.3°	253°

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.)

The orbital elements of C/2018 A3 (ATLAS) are:

            e (Eccentricity)                : 0.9904760
            q (Perihelion distance)         : 3.2937270
            i (Inclination)                 : 139.61070
            Ω (Longitude of ascending node) : 194.36010
            ω (Argument of perihelion)      : 86.51760
            L (Longitude of perihelion)     : 108.92816
            B (Latitude of perihelion)      : 40.29935
            T (Time of perihelion passage)  : 2458492.14120
            P (Orbital period in years)     : 6431.35

            Epoch                           : 2025 Jul 02
            Reference                       : MPEC 2021-P47

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

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. The gray curve is based on the absolute magnitude and slope parameter as calculated from the original MPEC, or the latest values provided by the MPC (8.50 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 8.11 + 5 log[∆] + 10.04 log[r]).

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-07-03 00:00 UT   00 01 23.9   -23 55 33    16.382   16.743  109.1    3.3   253   26.5 
2025-07-03 05:19 UT   00 01 23.0   -23 56 01    16.380   16.744  109.3    3.3   253   26.5 
2025-07-04 00:00 UT   00 01 19.8   -23 57 43    16.373   16.748  110.0    3.3   253   26.5 
2025-07-05 00:00 UT   00 01 15.4   -23 59 55    16.363   16.754  110.9    3.2   253   26.5 
2025-07-06 00:00 UT   00 01 10.8   -24 02 07    16.354   16.759  111.8    3.2   254   26.5 
2025-07-07 00:00 UT   00 01 05.9   -24 04 21    16.345   16.764  112.7    3.2   254   26.5 
2025-07-08 00:00 UT   00 01 00.8   -24 06 36    16.336   16.769  113.6    3.2   255   26.5 
2025-07-09 00:00 UT   00 00 55.4   -24 08 52    16.327   16.775  114.5    3.2   255   26.5 
2025-07-10 00:00 UT   00 00 49.8   -24 11 09    16.318   16.780  115.4    3.1   256   26.5 
2025-07-11 00:00 UT   00 00 44.0   -24 13 26    16.309   16.785  116.3    3.1   256   26.5 
2025-07-12 00:00 UT   00 00 37.9   -24 15 45    16.301   16.790  117.2    3.1   257   26.5 
2025-07-13 00:00 UT   00 00 31.6   -24 18 04    16.292   16.796  118.1    3.1   257   26.5 

    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.