The nights may be getting shorter, but it’s still the perfect time of year for a spot of star gazing. The neurobiology of low light vision suggests this isn’t a pastime to be rushed – be patient. Stepping outside for a couple of minutes isn’t enough. The longer you look up at the sky, the better your vision becomes. This is because it takes a few minutes for your pupils to dilate to let more light in. But the chemistry of the light detectors in your retina take half an hour or more to adjust, boosting your sensitivity to low light. This is at the cost of accuracy because your night vision is less able to perform fine discrimination and see colour. The eye quickly resets to day mode if you even glance at strong light so keep the brightness of your phone screen down if you’re using an astronomy app otherwise it will make the faint stars you’re looking at invisible.
All those memories of vivid starry nights on long outdoor evenings are subjective. The stars only appear brighter because you’re out for longer; the chemistry of your retina changes allowing your eyes to become dark adapted.
Dr Daniel Glaser is director of Science Gallery at King’s College London
