C/2023 A3 (Tsuchinshan-ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Today	25 Sep 2023	15.6	5.290 AU	6.121 AU	14h12m	-01°30'	31.4°	5.7°	91°
Perihelion	27 Sep 2024	0.2	0.391 AU	0.908 AU	10h46m	-06°03'	23.0°	92.1°	260°
Nearest approach	12 Oct 2024	-0.9	0.556 AU	0.472 AU	14h07m	-01°04'	15.3°	151.8°	64°

Please be aware that cometary behaviour is difficult to predict by nature. Predictions on this page are based on standard models and the latest observations available to me, and will gradually improve with time. The ability of comets to either disappoint or pleasantly surprise us, is one of many things that make them so interesting.

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/2023 A3 (Tsuchinshan-ATLAS) are:

            e (Eccentricity)                : 1.0001490
            q (Perihelion distance)         : 0.3914480
            i (Inclination)                 : 139.11900
            Ω (Longitude of ascending node) : 21.55690
            ω (Argument of perihelion)      : 308.48410
            L (Longitude of perihelion)     : 65.11978
            B (Latitude of perihelion)      : -30.81864
            T (Time of perihelion passage)  : 2460581.22260

            Epoch                           : 2023 Sep 24
            Reference                       : MPEC 2023-R20

            Classification(s):              : Nearly isotropic; New (a > 10000 AU)
        

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 (5.00 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 4.47 + 5 log[∆] + 10.00 log[r]). The additional green curve shows the effect of forward scattering, occurring when the comet is between the earth and the sun, for a gas-to-dust light ratio δ90 of 0.10. (See Marcus 2007)

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.