C/2021 Q3 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	15 Jan 2022	18.6	5.215 AU	4.878 AU	17h48m	+82°37'	104.7°	10.5°	331°
Perihelion	25 Jan 2022	18.6	5.214 AU	4.884 AU	18h24m	+84°24'	104.2°	10.5°	330°
Today	2 Oct 2026	24.4	12.165 AU	12.702 AU	08h51m	-16°07'	55.6°	3.9°	263°

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. (8.0 + 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/2021 Q3 (ATLAS) are:

    e (Eccentricity)                : 0.9298110
    q (Perihelion distance)         : 5.2142820
    i (Inclination)                 : 77.70500
    Ω (Longitude of ascending node) : 307.90330
    ω (Argument of perihelion)      : 114.17800
    L (Longitude of perihelion)     : 282.52778
    B (Latitude of perihelion)      : 63.04384
    T (Time of perihelion passage)  : 2459604.73770
    P (Orbital period in years)     : 640.31

    Epoch                           : 2026 Oct 01
    Reference                       : MPC194175

    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
2026-10-01 00:00 UT   08 50 58.1   -16 02 39    12.709   12.159   54.8    3.9   262   24.4 
2026-10-02 00:00 UT   08 51 07.3   -16 06 38    12.703   12.164   55.5    3.9   263   24.4 
2026-10-02 04:41 UT   08 51 09.1   -16 07 24    12.702   12.165   55.6    3.9   263   24.4 
2026-10-03 00:00 UT   08 51 16.3   -16 10 37    12.697   12.169   56.2    3.9   264   24.4 
2026-10-04 00:00 UT   08 51 25.0   -16 14 37    12.690   12.174   56.9    3.9   264   24.4 
2026-10-05 00:00 UT   08 51 33.4   -16 18 37    12.684   12.179   57.7    4.0   265   24.4 
2026-10-06 00:00 UT   08 51 41.6   -16 22 38    12.678   12.184   58.4    4.0   266   24.4 
2026-10-07 00:00 UT   08 51 49.5   -16 26 39    12.671   12.189   59.1    4.0   266   24.4 
2026-10-08 00:00 UT   08 51 57.1   -16 30 41    12.664   12.194   59.9    4.1   267   24.4 
2026-10-09 00:00 UT   08 52 04.5   -16 34 44    12.657   12.199   60.6    4.1   268   24.4 
2026-10-10 00:00 UT   08 52 11.5   -16 38 47    12.650   12.204   61.4    4.1   268   24.4 
2026-10-11 00:00 UT   08 52 18.3   -16 42 50    12.643   12.209   62.1    4.1   269   24.4 
2026-10-12 00:00 UT   08 52 24.8   -16 46 54    12.636   12.213   62.9    4.2   270   24.4 

    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.