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	14 May 2025	29.0	19.399 AU	18.674 AU	16h04m	+25°32'	134.8°	2.1°	193°

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
2025-05-14 00:00 UT   16 04 23.6   +25 31 16    18.669   19.395  134.8    2.1   194   29.0 
2025-05-14 20:29 UT   16 04 12.4   +25 32 06    18.674   19.399  134.8    2.1   193   29.0 
2025-05-15 00:00 UT   16 04 10.4   +25 32 14    18.675   19.400  134.8    2.1   192   29.0 
2025-05-16 00:00 UT   16 03 57.2   +25 33 11    18.680   19.405  134.7    2.1   191   29.0 
2025-05-17 00:00 UT   16 03 44.0   +25 34 05    18.687   19.411  134.6    2.1   190   29.0 
2025-05-18 00:00 UT   16 03 30.8   +25 34 56    18.693   19.416  134.5    2.1   188   29.0 
2025-05-19 00:00 UT   16 03 17.5   +25 35 45    18.699   19.422  134.4    2.1   187   29.0 
2025-05-20 00:00 UT   16 03 04.3   +25 36 32    18.706   19.427  134.3    2.1   185   29.0 
2025-05-21 00:00 UT   16 02 51.0   +25 37 17    18.713   19.432  134.2    2.1   184   29.0 
2025-05-22 00:00 UT   16 02 37.7   +25 37 59    18.720   19.438  134.0    2.1   183   29.0 
2025-05-23 00:00 UT   16 02 24.4   +25 38 39    18.728   19.443  133.8    2.2   181   29.0 
2025-05-24 00:00 UT   16 02 11.1   +25 39 16    18.735   19.448  133.6    2.2   180   29.0 

    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.