Averted vision

The retina at the back of your eye has two types of light-sensitive cell: about five million ‘cone’ cells form a central ring and respond to colour and brightly lit scenes; and around them are a hundred million ‘rod’ cells. It’s the rod cells that help you see things ‘out of the corner of your eye’ and in low light. Astronomers have found a way of using them to advantage. (You need to ‘dark-adapt’ your eyes first, though, by staying in the dark for twenty minutes or so.)

The night sky has a lot of stuff
That’s really hard to spot,
So use ‘averted vision’:
It’s like looking when you’re not.

Employ it when a galaxy,
A nebula, or star
Is just too faint for naked eyes
To see from where you are.

Here’s what you do. You need to know
Where, roughly, to expect it,
And then you focus to one side
And let your rods detect it.

What earlier you couldn’t see
Will now come into view –
As long as you don’t ‘look’ at it!
Seems crazy, but it’s true!

[Image: thepinksylphide.com]
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