C/2019 T4 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	4 Apr 2022	11.8	4.272 AU	3.325 AU	11h49m	-20°41'	158.5°	4.9°	48°
Perihelion	8 Jun 2022	12.1	4.237 AU	3.887 AU	11h51m	-07°33'	103.3°	13.5°	112°
Today	14 Oct 2025	18.7	10.025 AU	10.079 AU	18h29m	+30°02'	84.0°	5.7°	77°

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 1.6 + 5 log[∆] + 12.1 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/2019 T4 (ATLAS) are:

    e (Eccentricity)                : 0.9952070
    q (Perihelion distance)         : 4.2369180
    i (Inclination)                 : 53.62440
    Ω (Longitude of ascending node) : 199.89090
    ω (Argument of perihelion)      : 351.10840
    L (Longitude of perihelion)     : 194.58994
    B (Latitude of perihelion)      : -7.14887
    T (Time of perihelion passage)  : 2459739.19230
    P (Orbital period in years)     : 26282.33

    Epoch                           : 2025 Oct 12
    Reference                       : MPEC 2025-ST8

    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
2025-10-14 00:00 UT   18 29 24.1   +30 02 48    10.078   10.025   84.1    5.7    77   18.7 
2025-10-14 02:54 UT   18 29 26.0   +30 02 18    10.079   10.025   84.0    5.7    77   18.7 
2025-10-15 00:00 UT   18 29 39.7   +29 58 42    10.093   10.030   83.5    5.7    76   18.7 
2025-10-16 00:00 UT   18 29 55.7   +29 54 38    10.108   10.036   83.0    5.7    76   18.7 
2025-10-17 00:00 UT   18 30 12.1   +29 50 37    10.124   10.042   82.5    5.6    75   18.7 
2025-10-18 00:00 UT   18 30 28.9   +29 46 37    10.139   10.048   81.9    5.6    74   18.7 
2025-10-19 00:00 UT   18 30 46.0   +29 42 40    10.155   10.054   81.4    5.6    73   18.8 
2025-10-20 00:00 UT   18 31 03.5   +29 38 45    10.170   10.059   80.8    5.6    73   18.8 
2025-10-21 00:00 UT   18 31 21.3   +29 34 52    10.185   10.065   80.3    5.6    72   18.8 
2025-10-22 00:00 UT   18 31 39.6   +29 31 02    10.201   10.071   79.7    5.6    71   18.8 
2025-10-23 00:00 UT   18 31 58.1   +29 27 14    10.216   10.077   79.2    5.6    70   18.8 
2025-10-24 00:00 UT   18 32 17.1   +29 23 29    10.231   10.083   78.6    5.6    70   18.8 

    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.