To look through even a small telescope at the greatness of the sky is a heady thing. It is not just the aesthetic delight of stars like grains of sand, or cloud-decked galaxies like tiny hurricanes in seas unseen; nor is it merely the knowledge of immensity that comes with understanding that each grain is a sun bright and ancient, each cloud an unknowable plurality of worlds. It is the sheer cosmic kick that comes from having the rods and cones of your retina stirred by photons that have been travelling for so long that mountains once young have crumbled to the sea. A ray of light that begins in another galaxy and ends in your nervous system is a miracle never to be tired of.

This continuing appeal of amateur astronomy should, light pollution permitting, see children and pensioners in their back gardens and up their local hills for as long as there are telescope makers to satisfy them. Online services such as Google Sky and Microsoft's new WorldWide Telescope allow users to scan the sky at higher resolution and in more wavelengths than amateurs could ever do, yet there is no reason to fear that they will bring those skywatchers indoors for good. Quite the reverse: their on-screen wonders feed the appetite to see for yourself.

Better still, the Internet allows the aggregation of observing time — both for those with telescopes and without. Amateurs following up newly discovered asteroids get the orbital elements from the website of the International Astronomical Union's Minor Planet Center. Galaxy Zoo, a site where a million galaxies await classification, puts the profusion of amateur eyeballs to further use, and has produced not only an unexpected level of interest but also some sound publications. Harnessing the pattern-recognition skills of people around the world who have no astronomical equipment other than a broadband connection may permit a range of similar projects in the future, as new surveys produce images at ever greater rates.

The Astrometry.net software we report this week (see page 437) offers new ways for the Internet to combine the observations of amateurs and professionals, past and present. It aims to provide the correct spatial and temporal coordinates for any picture of the sky submitted to it, be it a recent CCD file or a glass plate found in Great-Aunt Herschel's attic. Its creators hope, with suitably astronomical ambition, to identify, and possibly assimilate, every image of the sky ever made. In doing so, they imagine discovering new truths about the way the sky changes over time — to recognize the transient, the unexpected, the hitherto unnoticed but nevertheless captured.

This is the sort of totalizing impulse that normally deserves scepticism, if not disquiet. In this case, though, it is hard not to see it as noble. The idea that all the solitary skywatchers are engaged in a single study, linked by ties of knowledge even as they stare upwards on their own, has always had its poetic truth. To make it practically true is a fine aspiration. Walt Whitman's poetic narrator may have

Wander'd off by myself, In the mystical moist night-air, and from time to time, Look'd up in perfect silence at the stars

— but there is no need to reject the learned astronomers' proofs and figures, charts and diagrams in order to experience that which enriches the soul. Observers of all sorts will soon be able to add to the glories of the endlessly interconnected inner world of the Internet while losing nothing of that precious and primal communion with the cosmos.