Bright emission nebulae

The bright colours of the Orion Nebula look very different through the eyepiece

The image of the Orion Nebula, M42, shown here is fairly typical of how this spectacular object – a glowing cloud of gas with an embedded, nascent, star cluster – and others like it are revealed in long-exposure astrophotography. The vast swathes of hydrogen that make up the bright so-called ‘emission’ nebula shine with vibrant shades of pink and red, while the darker regions harbour subtle dust clouds with swirling filament-like forms.

Though these kinds of pictures of starforming nebulae are ubiquitous in the world of imaging, they are nonetheless taken with cameras that are far more capable of detecting and collecting celestial light than our eyes, and so the visual impression of these objects in a small- to medium-aperture telescope is markedly different.

With some of the northern sky’s most famous bright nebulae, from a site with relatively dark skies like the Orion Nebula and the Lagoon Nebula, you will be able to detect the soft glow of the nebulae around their embedded star clusters. In the case of M42 it’s possible to see some of the brighter structures surrounding the Trapezium Cluster in a small telescope (see the eyepiece sketch, right), but there will be no dazzling colours.

Brightness and detail-wise, things improve if you use a larger aperture instrument and, perhaps, a light-pollution suppression or contrast-enhancing filter. In the largest instruments – think huge Dobsonian light buckets – M42 and the Lagoon Nebula can reveal breathtaking structure, and you’ll start to see more details in some of the fainter emission nebulae too. But, again, the reds and pinks of astrophotos will not be there. At most, in our experience, you might detect a slight hint of a mint-green hue.