C/2017 T3 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	19 Jul 2018	9.1	0.821 AU	1.418 AU	06h44m	-09°11'	34.7°	44.8°	210°
Nearest approach	1 Aug 2018	9.2	0.858 AU	1.347 AU	08h08m	-20°29'	39.6°	48.9°	195°
Today	9 Aug 2025	29.2	19.862 AU	19.820 AU	15h50m	+24°40'	90.9°	2.9°	108°

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/2017 T3 (ATLAS) are:

            e (Eccentricity)                : 0.9993860
            q (Perihelion distance)         : 0.8213790
            i (Inclination)                 : 88.29950
            Ω (Longitude of ascending node) : 230.26570
            ω (Argument of perihelion)      : 246.77190
            L (Longitude of perihelion)     : 234.22102
            B (Latitude of perihelion)      : -66.71318
            T (Time of perihelion passage)  : 2458319.25380
            P (Orbital period in years)     : 48928.61

            Epoch                           : 2023 Sep 24
            Reference                       : MPC114600

            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 (10.00 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 9.27 + 5 log[∆] + 10.39 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
2025-08-09 00:00 UT   15 50 24.1   +24 40 31    19.814   19.860   91.1    2.9   108   29.2 
2025-08-09 06:58 UT   15 50 23.4   +24 40 00    19.820   19.862   90.9    2.9   108   29.2 
2025-08-10 00:00 UT   15 50 21.8   +24 38 46    19.832   19.866   90.4    2.9   107   29.2 
2025-08-11 00:00 UT   15 50 19.8   +24 36 59    19.850   19.871   89.7    2.9   107   29.2 
2025-08-12 00:00 UT   15 50 17.9   +24 35 13    19.867   19.876   89.0    2.9   106   29.2 
2025-08-13 00:00 UT   15 50 16.3   +24 33 25    19.885   19.882   88.3    2.9   105   29.3 
2025-08-14 00:00 UT   15 50 14.8   +24 31 37    19.903   19.887   87.6    2.9   105   29.3 
2025-08-15 00:00 UT   15 50 13.6   +24 29 49    19.920   19.892   86.9    2.9   104   29.3 
2025-08-16 00:00 UT   15 50 12.6   +24 27 59    19.938   19.898   86.2    2.9   103   29.3 
2025-08-17 00:00 UT   15 50 11.8   +24 26 10    19.955   19.903   85.5    2.9   103   29.3 
2025-08-18 00:00 UT   15 50 11.2   +24 24 20    19.973   19.908   84.9    2.9   102   29.3 
2025-08-19 00:00 UT   15 50 10.9   +24 22 29    19.991   19.914   84.2    2.9   102   29.3 

    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.