A short-period comet that goes round the Sun every 5.4 years, at perihelion in August 2026
Past its best. Still a target for a camera from Georgetown until about 11 November 2026.
Past its best. Still a target for a camera from Georgetown until about 11 November 2026.
Tonight from Georgetown it is highest at 9:39 pm GYT, 51 degrees up in the south (halfway up). When the sky turns fully dark at 6:50 pm it stands 34 degrees up in the south-east. It sinks below 20 degrees at 1:44 am. It is at least 10 degrees up for 7.7 hours of darkness.
At about magnitude 10.1 (measured) it reads 10.2 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 tonight it is a target for a camera.
From Lethem, under a dark interior sky: Past its best. Still a target for a small telescope from Lethem until about 15 December 2026. Tonight it reads 10.2 there against a small telescope limit of 10.2.
Face south (azimuth 180 degrees) at 9:39 pm GYT and look halfway up, 51 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 43 degrees to the left of straight up. It is 132 degrees from the Sun in the sky and 145 degrees from the Moon, which is 3% lit.
Against the stars it moves about 44 arcseconds an hour, so it is in the same field of view all night and a little further along the next night.
A window is a run of nights on which it is at least 10 degrees up with the Sun at least 12 degrees down and its forecast brightness reaches a camera or better from Georgetown. The forecast is pinned to observers' reports from this return.
From 29 April to 10 July 2027 it is hidden in the Sun's glare from Georgetown: 73 nights.
From 16 June to 16 August 2028 it is hidden in the Sun's glare from Georgetown: 62 nights.
| In reach | Best night | Best time | Height and direction | Gear on the best night | Forecast magnitude | Nights at each rung |
|---|---|---|---|---|---|---|
| 8 October to 11 November 2026 | 8 October 2026 | 9:41 pm GYT | 51 degrees, south | Camera | about 10.1 (likely 9.2 to 11.0) | 35 camera |
Observers reporting to COBS measured it at about magnitude 10.1: the median of 18 reports of every kind (camera measurements included) from 6 observers in the 10 days to 6 October 2026, ranging from 9.7 to 10.4. It is fading.
The forecast is pinned to those reports and fades or brightens with distance on a slope of 22.4 magnitudes per tenfold change in Sun distance. It is good for a couple of weeks; beyond that its range widens.
On its best night from Georgetown, 8 October 2026, it could be about 10.1 (likely 9.2 to 11.0), reading 10.2 through the air. Chance of the naked eye: no real chance. Binoculars: no real chance. A small telescope: about 2%. The range is one standard deviation either side: about two forecasts in three land inside it.
Catalogue estimates, shown as a cross-check and never as how bright it will look: JPL's law gives 14.1 tonight and the Minor Planet Center's gives 14.4. 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.
Tonight: aim at azimuth 180 degrees, altitude 51 degrees, at 9:39 pm GYT. The sky is dark from 6:50 pm to 4:30 am.
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.
10P/Tempel 2 passed closest to the Sun (perihelion) on 2 August 2026, at 1.418 au, where 1 au is the Earth's distance from the Sun. One orbit takes 5.37 years. The orbit is tilted 12.0 degrees to the Earth's and its eccentricity is 0.5374 (0 is a circle, 1 an open curve).
Tonight it is 1.58 au from the Sun and 0.73 au from Earth, moving away from the Sun.
Orbit: NASA/JPL Horizons osculating elements, solution JPL#K265/56, 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.
10P/Tempel 2 is a short-period comet that goes round the Sun every 5.4 years. The "P" in 10P marks a periodic comet, and the number is the order in which its return was first confirmed.
Brightest eye estimate reported to COBS on each past return: 2010: magnitude 7.6, 34 days after perihelion, 1.47 au from the Sun and 0.66 au from Earth; 2015: magnitude 9.2, 17 days after perihelion, 1.43 au from the Sun and 1.91 au from Earth; 2021: magnitude 10.1, 17 days after perihelion, 1.42 au from the Sun and 2.16 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. "Measured" means: Observers measured this in the last 10 days.
Gear rungs and ranges are estimates for a typical observer: your eyes, your sky and the night will differ.