How to spot a comet


Anyone who’s even vaguely acquainted with goings-on in the night sky knows that at the moment Comet NEOWISE – brightest comet since the last Bright Comet – is visible (just) with the naked eye, in the North-West in the evening twilight, and the North-East before dawn.

I’ve been around for long enough to have been promised Kohoutek  (1974), Halley  (1986), and McNaught (2007) none of which exactly came good with the promise of actually, you know, shining in the night sky, in a Hemisphere near me. Or on the one occasion when they did (Hale-Bopp, 1997), I was living in rain-soaked, brightly-illuminated Glasgow city centre without the means to get to a rural dark sky devoid of clouds.

But this time it looked as if I was in with a chance of spotting an actual comet.

Viewed from as far North as our house, NEOWISE is circumpolar. That is, it sits day and night in the Northern skies going round and round the Pole Star and never setting. The only things that stop you seeing it are daylight (between about 3:30 a.m. and 11:30 p.m.), clouds (depressingly common here, though not as much so as in Glasgow), and other sources of light (street-lighting and the like).

NEOWISE also had the good grace to stay around for long enough to give the Average Brit a chance of at least one clear evening in which to try and find it.

We picked our clear evening, on Thursday.

We set off to the local playing field, which offers reasonable darkness (for urban surroundings like ours) and a view to down within about 5 degrees of the Northern horizon. The instructions I’d read said the comet should be visible from (and I quote) ‘just after sunset’.

Of course all we saw in the hour after sunset was twilight, and no actual astronomical objects at all – not even the brightest of the stars.

But our house boasts a North-facing attic Velux window, high enough up that our front garden trees block the nearest streetlight and the view extends down to the horizontal. We stationed ourselves there, complete with cushions to lean on, at about 10 p.m., and waited.

It wasn’t until after half past that my daughter spotted the first star. It was so faint that it could easily be mistaken for an illusion. The only way either of us could make sure it wasn’t one was by not-staring at it in such a way that it didn’t appear to move. Strangely, looking just to one side of it made it appear more distinct – something to do with how the various receptors (rods and cones) are arranged on the retina of the human eye.

Here’s my problem – the one which means that, though I have a degree in ‘Physics with Astronomy’, I am no astronomer. NEOWISE is best viewed – or at least found – using binoculars. I can’t use binoculars. I have no stereoscopic vision, and I use glasses with very different prescriptions for the 2 eyes. And before you ask, using a typical telescope with glasses is pretty hit-and-miss too. My chances of spotting anything in the night sky, binoculars or no, are minimal. I am also, though, astronomically stubborn. And so is my daughter (who has perfect eyesight).

So we stayed, gazing philosophically out at the sky and at our streetscape, the occasional post-lockdown reveller, and the low bar of cloud between the North and North-West horizon, watching stars appear one by one, until after midnight. We talked, sporadically (the best conversations are always sporadic), about all sorts: The research she’s doing, music (complete with lyrics), the smell of the evening air…

At half past midnight we decided that the low bar of cloud was going nowhere, the comet was most likely hiding behind it, and we’d call it a night. The weather forecast gave clouds by dawn, so it wouldn’t be worth our while getting up in 3 hours’ time to try and catch NEOWISE as it rose beyond the horizon fug again.

However, the sky is clear tonight…

(Picture not mine, of course. It’s from the i newspaper)