C/2025 R1 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	13 Oct 2025	18.2	2.037 AU	1.649 AU	19h13m	+77°12'	97.6°	29.1°	88°
Perihelion	23 Nov 2025	18.5	1.975 AU	2.012 AU	18h46m	+41°38'	73.6°	28.7°	42°
Today	11 Jan 2026	19.2	2.062 AU	2.603 AU	19h14m	+25°01'	47.0°	20.4°	355°

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. The light curve is based on the absolute magnitude and slope parameter as calculated from an MPEC, or the latest values provided by the minor planet center. (14.0 + 5 log[∆] + 10.0 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/2025 R1 (ATLAS) are:

    e (Eccentricity)                : 0.9881130
    q (Perihelion distance)         : 1.9752080
    i (Inclination)                 : 110.02730
    Ω (Longitude of ascending node) : 60.39690
    ω (Argument of perihelion)      : 77.55160
    L (Longitude of perihelion)     : 3.20216
    B (Latitude of perihelion)      : 66.55490
    T (Time of perihelion passage)  : 2461002.83770
    P (Orbital period in years)     : 2141.96

    Epoch                           : 2026 Jan 10
    Reference                       : MPEC 2026-A24

    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
2026-01-10 00:00 UT   19 13 23.7   +25 13 03     2.593    2.058   47.3   20.6   357   19.2 
2026-01-11 00:00 UT   19 13 54.0   +25 03 14     2.601    2.061   47.1   20.4   355   19.2 
2026-01-11 05:00 UT   19 14 00.2   +25 01 14     2.603    2.062   47.0   20.4   355   19.2 
2026-01-12 00:00 UT   19 14 23.9   +24 53 45     2.609    2.065   46.8   20.3   354   19.2 
2026-01-13 00:00 UT   19 14 53.5   +24 44 34     2.616    2.068   46.6   20.2   353   19.2 
2026-01-14 00:00 UT   19 15 22.7   +24 35 42     2.624    2.072   46.4   20.1   352   19.3 
2026-01-15 00:00 UT   19 15 51.5   +24 27 07     2.631    2.076   46.2   20.0   350   19.3 
2026-01-16 00:00 UT   19 16 19.9   +24 18 51     2.637    2.079   46.1   19.9   349   19.3 
2026-01-17 00:00 UT   19 16 47.9   +24 10 51     2.644    2.083   45.9   19.8   348   19.3 
2026-01-18 00:00 UT   19 17 15.5   +24 03 08     2.650    2.087   45.8   19.8   347   19.3 
2026-01-19 00:00 UT   19 17 42.6   +23 55 43     2.656    2.091   45.7   19.7   345   19.3 
2026-01-20 00:00 UT   19 18 09.3   +23 48 33     2.661    2.095   45.6   19.6   344   19.3 
2026-01-21 00:00 UT   19 18 35.6   +23 41 40     2.667    2.099   45.6   19.6   343   19.3 

    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.