Earth light diminishes the beauty of the stars

The returning swirl of Atlantic cloud put an end to those frosty Finlandian nights and the rapture of the stars

The returning swirl of Atlantic cloud put an end to those frosty Finlandian nights and the rapture of the stars. Rare nights like those should bring exhortations from the weatherpeople on the telly: "If you're living out of town, switch off everything, get out there - look up!".

According to the International Dark-Sky Association (based in Tucson, Arizona) about 2,500 stars should be visible to the human eye in any unpolluted night sky. Here under Mweelrea Mountain I've never bothered counting, but feel I could scan ten times that many before swooning through the middle of the Milky Way.

A lot of the magic is the enveloping darkness on this side of the hill, still more or less intact despite the chilly flares of farm yard-lights and the twinkling necklace strung out to Renvyle, across the sea in Connemara.

Westward, Inishturk and Inishbofin float in the ocean like lighted liners at anchor: there should be distant violins.

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In the average suburb, however, where light-spill bounces off the muck in the air, the number of visible stars is reduced to two or three hundred, and in O'Connell Street the brightest celestial orb will be the light on the top of the Spire. How far out into the hills would one have to drive the children to show them an awe-inspiring, pristine view into space? This Christmas swept a positive aurora of light through the countryside, as a whole new range of illuminations brought stars and Santas to a thousand gables and fibre-optic icicles shimmering along the eaves.

Festivals are meant to be festive, but did this unprecedented riot of light soften us up for yet more "security" lights, floodlights, gate and garden-path lights powered by the sun? How many more rural communities, well able for generations to see their way home but now apparently blind at anything less than 150 watts, will demand fresh rows of street lamps to help them find their car keys? In North America, which glows beneath space at night like a bed of fiery magma (see the NASA image of earthlights at www.cojoweb.com/earthlights.html), the Canadian city of Calgary is leading the way back to more sustainable illumination with properly down-shielded streetlights with flat lenses and lower wattage. In the Czech Republic, where the fall of communism was celebrated in a blaze of neon and floodlit advertising, astronomers have succeeded in the world's first countrywide law to reduce light pollution, defined as "every form of illumination by artificial light which is dispersed outside the areas it is dedicated to . . ." (How this would have tickled Johannes Kepler, whose astronomy was done by candelight in Prague).

In Ireland, the local authorities control public lighting, but the ESB instals and maintains it and advises on design. In the 1960s and 1970s, most road lighting used high-pressure mercury vapour lamps in post-top lanterns which spilled a lot of light upwards. These are now being replaced nationwide by more energy-efficient sodium lighting in side-entry lanterns that direct more of their light on to the road.

The high-pressure sodium lamp, with its golden-white light, is used in town centres, where its warm glow and fairly natural rendering of colours are appreciated. Elsewhere, the low-pressure sodium lamp (SOX) casts its balefully monochrome (but 35 per cent cheaper) light across the road - and, in the lamp's currently bulky form, still rather too much into-sky glow. The ESB's Michael Perse, public lighting engineering manager, tells me of trials in the midlands of an SOX lantern with a better system of reflectors.

Flat-bottomed lanterns would spread even less light off the road (they're used at airports), but would need a closer spacing to give an even illumination.

Ironically, however alien the amber glare of SOX illumination may seem, it is probably more ecologically friendly. Just as badgers seem able to ignore being watched by red light, beach-nesting turtles seem less confused by sodium light than other kinds. Moths, too, show a less fatal attraction to it. And even astronomers near motorways can filter out its narrow spectrum.

A trip into the ivy-hung, somewhat haunted countryside beyond Lough Corrib had me imagining the serenely unpolluted sky in which "a church mouse amateur" among Irish astronomers, John Birmingham of Millbrook House, Co Galway, spotted a brand new star back in 1866.

He noticed it while walking home near midnight on May 12th - an incandescent nova in the Northern Crown - and told the London Times , whose editor promptly binned his letter. But he eventually got his gold medal from the Royal Irish Academy and now, after long neglect, inspires a weighty and even impassioned biography.

Its author, Paul Mohr, recently-retired from the Department of Geology at UCG, has himself been a lyrical seeker in the landscape and skies of the west - even a poet, if not quite on his subject's heroic, satirical scale.

Drawn originally to Birmingham's geological speculations among the eskers and erratic boulders of Galway, he has traced the making of a polymath, Catholic, minor landlord, living in uneasy times, who went on to discover 49 red stars from the little wooden observatory in his garden. He conjures the spirited intellect that could dwell in our Victorian backwoods, with their starry, starry nights.

John Birmingham, Esq., Tuam and Ireland's New Star, published by Millbrook Nova Press, Tóin an Gharráin, Cor an Dola, Co na Gaillimhe, is available in Galway bookshops at €30.