Comet C/2001 Q4 (NEAT): the naked-eye comet of May 2004

This page dates from May 2004, when Comet C/2001 Q4 (NEAT) was the comet of the season for southern observers. It has been rewritten as a look back at the comet and a guide to finding the comets in the sky now.

The comet

C/2001 Q4 was discovered in August 2001 by the Near-Earth Asteroid Tracking survey, the same programme that found Comet NEAT C/2002 V1 the following year. Its name tells the story of its discovery: a non-periodic comet (C/), found in 2001, the fourth reported in the second half of August (Q4).

Unlike its sungrazing cousin, Q4 never went especially close to the Sun. Its perihelion in mid-May 2004 was at about Earth's own distance from the Sun. What made it a good show was its approach to Earth: in early May it passed within about a third of the Earth-Sun distance of us, and it did so while well placed in the southern sky.

A southern hemisphere comet

Through late April and early May 2004 the comet was best seen from the southern hemisphere. From New Zealand it was visible in the evening sky, moving through the southern constellations and climbing higher each night. From a dark site away from town lights it reached naked-eye visibility as a soft, fuzzy patch, with the tail showing better in binoculars and photographs.

As May went on, the comet moved quickly northwards across the sky. It passed through the area near the bright stars of Canis Major and Puppis, then continued north, and by the second half of May it was sinking into the evening twilight for us while becoming a northern hemisphere object. Its fast motion meant you could see its position shift against the stars over an hour or two through binoculars.

The binocular view

In 7x50 or 10x50 binoculars the comet showed a round, bright coma with a brighter centre, a greenish tint in photographs, and a tail extending away from the Sun. The coma looked large because the comet was close to Earth. Under good skies the tail could be traced for several degrees in long exposures.

The Moon matters with comets like this. A bright Moon washes out the fainter outer coma and tail, so the best views come in the darker part of the lunar cycle.

Finding current comets

Bright naked-eye comets turn up only every few years, but there are usually a few comets within reach of binoculars or a small telescope. To find them:

1. Check the ephemerides. The Minor Planet Center's comet ephemeris service lists observable comets with positions and predicted brightness. Look for those brighter than about magnitude 9 for binoculars.
2. Plot the position. Load the comet into planetarium software such as Stellarium, which can download comet orbital elements, so you can see where it sits against the stars from your location.
3. Watch the predicted brightness with caution. Comets are unpredictable. Some brighten well beyond forecasts; others fade or break apart.
4. Go dark. A comet that is easy from a rural site may be invisible from a city backyard.
5. Check local news from your society. Astronomical societies often share finder charts when a good comet is about.

For the practical side of spotting comets low in twilight, see the tips on the Comet NEAT C/2002 V1 page.