Why can you see faint stars bet­ter if you don’t look di­rectly at them?

BBC Earth (Asia) - - Q & A - RM

Astronomers call the tech­nique ‘averted vi­sion’, and it ex­ploits the fact that our eyes con­tain two types of light-de­tect­ing cells. Around the cen­tre of the retina are so-called cone cells, which give us colour vi­sion and need good light lev­els. Away from the cen­tre are rod cells, which are re­spon­si­ble for black-and-white vi­sion, and work bet­ter than the cone cells at low light lev­els. Look­ing off to one side al­lows more light from faint ob­jects to strike the rod cells, and be­come vis­i­ble to us.

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