As an observational astronomer, I get to travel to various supposedly exotic locations. People get envious when I tell them I'm going to Hawaii to observe, and they don't believe me when I tell them that to me, Hawaii is a cold windswept mountaintop, working nights.

Of course it's not just the cold and the nights that are the problem. At 14,000 feet, the Mauna Kea Observatory on the Big Island is above a third of the atmosphere. Nothing about the human body works properly at this altitude unless you've done some serious acclimatization, and even then things can go wrong. Observers sleep, when they can, at the accommodation block at 10,000 feet, but this is never restful when you're spending twelve or more hours a night on the summit. And when you're on the summit things can get quite strange.

My first observing trip provided a useful demonstration of this. You expect to get out of breath easily, and the infamous staircase at the UK Infrared Telescope (UKIRT), from the control room down to the toilets, is a case in point. It's short enough to run up, but at 14,000 feet you should never try to do this unless you like hypoxia.

But what gets to you is the unexpected.

I am sitting at a workstation, examining some of my data, when I get the feeling I'm forgetting something important. I check around me to make sure the telescope's not stopped and that we're still taking data. No trouble there. I check the weather monitor to see if the clouds are rolling in. Nothing there either, and these problems seem rather too distant, too impersonal to be what's worrying me.

I'm forgetting something important, that I do all the time by instinct or reflex, but that isn't currently working.

Breathing.

Yes, that's it!

A few deep inhalations later and I'm feeling much better, and my CO2 levels are back to the point where they can trigger the reflex again.

It's not just small problems like forgetting to breathe that make the mountain hazardous, though. You lose IQ points the higher you go, and this can affect you in very strange ways. It's the things you least expect that catch you out, evn when it comes to the simple set-up procedures. For example, we managed to waste fifteen minutes one night working out how to align an instrument on the sky – just because we couldn’t remember which way was east.

But observers have to face only a limited set of problems. Those building telescopes have to face new issues throughout the day as they assemble some of the most complicated constructions on the planet. And altitude doesn't help.

Hence this conversation reputedly overheard at the construction site of an observatory that shall remain nameless:

Construction worker at the summit: We have a problem with this particular part.

HQ at sea level: Oh yes? What is it?

CW: It's the wrong size.

HQ: The wrong size?

CW: Yes – I've cut it three times, and it's still too short!

HQ: Come down the mountain – now!

Fortunately the effects of the altitude aren't permanent. Once you're at sea level everything goes back to normal. In fact, it's a little better than normal after any time at the summit. You're suddenly reminded just how much air there is, how much oxygen there is in it – and that breathing is not a major form of exercise.