Comet Hale-Bopp from 1997

What do you do when you're stuck inside and can't go to any dark sky sites? You rummage through old photos.

This photo was taken in April 1997 - just over 23 years ago now. My wife and I were living in Bergen in Norway while Jan did a post-doctoral fellowship at the University there. I had little to do apart from do a series of Language and Culture course and act as a tour guide for visiting friends, including Marilyn.

Like me, Marilyn is a birdo and an astronomer. However, at that stage I wasn't into birds. It was Marilyn's visit that set me on that particular course, and she became my much-respected birding mentor. But that's not what I'm talking about here.

The comet behind the three of us is C/1995 O1 Hale-Bopp. This is probably the most well-known comet after Halley, and it was observed for over a year during its bright and spectacular 1997 flyby.

Most comets are periodical, meaning they return regularly. This is because they're in orbit around the sun - albeit a highly elliptical one. Originally, Hale-Bopp's orbit was so large that it probably wasn't ever expected back. However, a close pass to Jupiter changed its orbit. It's now expected back in the year 4385.

The other unusual thing about the comet was that it had non-ionised particles in its tail. You can - nearly - see them as a straight line pointing directly upwards in the photo. Others got better photos.

For the technically-minded, the photo was taken at about 21:30 (UTC+1) on 5 April 1997. I used a 35mm film camera, a Pentax Super A, and shot on ISO 800 film. The exposure was 15 seconds. The three young, out-of-focus blobs in the foreground are (from left) Jan, Marilyn and yours truly.

It was a cold night. Thanks to the Norwegian obsession with record-keeping and, I can tell you it was 1.9° at the time.

At that point, Hale-Bopp was between the constellations of Perseus and Andromeda. That's Algol (β Persei) above and to the left of the comet and Almach (γ Andromedae) to the right.