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Star-hopping: finding deep-sky objects by eye

Star-hopping is the skill of finding a faint object by stepping from bright naked-eye stars to fainter ones along a chart until the target is in the field. It is how observers found the sky for centuries.

The idea

Most deep-sky objects are too faint to see with the naked eye, but they sit in known positions relative to stars you can see. Star-hopping means starting at a bright star near the target, then using a chart and a low-power, wide-field eyepiece or a finder to move in short, recognisable steps, star pattern by star pattern, until the object drifts into view.

It turns finding an object into a small navigation puzzle, and unlike a computer it teaches you the sky, so the constellations and their objects become familiar.

What you need

You need a chart or app that shows stars to about the depth your finder reaches, a good finder or a wide-field low-power eyepiece giving the largest true field your telescope allows, and a red torch to read the chart without spoiling your night vision.

A wide true field is the key eyepiece property for hopping: the more sky you can see at once, the easier it is to recognise the star patterns on your chart. A telescope's focal length divided by your eyepiece's focal length gives the magnification, and the eyepiece's apparent field divided by that gives the true field.

How to practise

Start with easy, bright targets whose location you can find from memory, like the Orion Nebula below Orion's belt or the Andromeda Galaxy from the corner of the Square of Pegasus. Learn those hops, then take on fainter objects near stars you now know.

Use the Fit My Telescope tool to find which of your eyepieces gives the widest true field, and keep that one as your finder eyepiece for hopping before switching to more power once the object is centred.

Related

Sources: Star hopping (Wikipedia, CC BY-SA) · Telescope Optics, Rutten and van Venrooij; Sky & Telescope optics primers