Master the art of averted vision

If you're new to stargazing, a faint object like C/2022 E3 ZTF, the comet that had us all excited earlier this year, isn't the best target for a first look through a telescope - the chances are you won't see a thing.

- Martin Mobberley 

The eye is a remarkable detector, but to see faint objects like this it helps to understand both its limitations and the tricks you can use to coax the maximum out of its short-exposure capability (unlike a DSLR camera, long exposures aren't an option with the eye).

Of course there are other limiting factors. Light pollution, impatience, a poor night for seeing, and not spending long enough dark-adapting your eyes can all play a part, as can using the wrong magnification and not keeping your telescope's optics clean and well-collimated. But by mastering 'averted vision', you can train your eyes to get the most out of your observing nights and use your retina to greatest effect.

The retina is the thin layer of cells that line the back of the eyeball, where light entering from the pupil is converted into signals for the brain. The eye has two types of detector cells within the retina, called rods and cones. Rods are low-light detectors, whereas cones allow full-colour, high-resolution eyesight. The central one degree of the retina, the fovea, is packed with cones which you are using to read this sentence. Your brain creates the illusion that the whole magazine page is sharp, but in fact you are only seeing a few letters at a time at high resolution and in full colour; your eye muscles are swiftly zipping everywhere and creating the illusion.

Find your sensitive side