A short-period comet that goes round the Sun every 13.6 years, at perihelion in August 2021
Last at perihelion in August 2021. Next return about 2035.
Last at perihelion in August 2021. Next return about 2035.
Tonight from Georgetown it is highest at 6:50 pm GYT, 60 degrees up in the south-west (high up). When the sky turns fully dark at 6:50 pm it stands 60 degrees up in the south-west. It sinks below 20 degrees at 9:41 pm. It is at least 10 degrees up for 3.5 hours of darkness.
At about magnitude 28.5 (forecast) it reads 28.6 through the air at that height. From Georgetown's sky, where the faintest star overhead is about magnitude 4.3, a comet has to read 3.3 for the naked eye, 6.8 for binoculars, 8.4 for a small telescope and 12.1 for a camera. So it is out of reach tonight.
From Lethem, under a dark interior sky: Last at perihelion in August 2021. Next return about 2035.
Face south-west (azimuth 241 degrees) at 6:50 pm GYT and look high up, 60 degrees above the horizon. A fist held at arm's length covers about 10 degrees.
A comet's gas tail points away from the Sun: at that minute the anti-Sun direction leans 24 degrees to the left of straight up. It is 81 degrees from the Sun in the sky and 102 degrees from the Moon, which is 3% lit.
Against the stars it moves about 4 arcseconds an hour, so it is in the same field of view all night and a little further along the next night.
Nobody has reported its brightness to COBS in the last 30 days, so every number here is a forecast.
No one has followed this comet through a return like this one, so the forecast is a catalogue estimate with a wide range.
Catalogue estimates, shown as a cross-check and never as how bright it will look: JPL's law gives 24.1 tonight and the Minor Planet Center's gives 33.0. Catalogue laws missed this season's measured comets by 2 to 4.5 magnitudes.
A comet's light is spread over a fuzzy patch, so it is harder to see than a star of the same magnitude. That is why the gear rungs ask for a magnitude in hand.
On a fixed tripod keep each exposure short enough that the stars stay round, then stack many frames. For a long stack, align on the comet as well as on the stars: it drifts against them from frame to frame. A dark site adds more than any lens.
8P/Tuttle passed closest to the Sun (perihelion) on 29 August 2021, at 1.023 au, where 1 au is the Earth's distance from the Sun. One orbit takes 13.63 years. The orbit is tilted 55.0 degrees to the Earth's and its eccentricity is 0.8208 (0 is a circle, 1 an open curve).
Tonight it is 9.95 au from the Sun and 10.06 au from Earth, moving away from the Sun.
Orbit: NASA/JPL Horizons osculating elements, solution JPL#K215/24, retrieved 8 October 2026. Positions on this page are computed from them in your browser and agree with JPL's own tables to half an arcminute.
The parent of the Ursid meteors of late December.
8P/Tuttle is a short-period comet that goes round the Sun every 13.6 years. The "P" in 8P marks a periodic comet, and the number is the order in which its return was first confirmed.
Its dust is the source of the Ursids meteors: each year the Earth crosses the trail it has left along its orbit.
Brightest eye estimate reported to COBS on each past return: 2008: magnitude 5.1, 23 days before perihelion, 1.09 au from the Sun and 0.26 au from Earth. How bright a return looks depends as much on how near the Earth it passes as on the comet.
Orbits: NASA/JPL Horizons (Giorgini, JD and the JPL Solar System Dynamics Group), data retrieved 2026-10-08.
Catalogue brightness laws: JPL Small-Body Database and the IAU Minor Planet Center.
Observed brightness: COBS Comet Observation Database (https://cobs.si) and its contributing observers, CC BY-NC-SA 4.0.
Data updated 8 October 2026. "Early forecast" means: A catalogue estimate. Early predictions are often wrong in both directions.
Gear rungs and ranges are estimates for a typical observer: your eyes, your sky and the night will differ.