Remember this figure for the eclipse that will cross the Iberian Peninsula on 12 August.
Keeping that date in mind, the ISO number (International Organization for Standardization) of the special glasses that must be used to view this once-in-a-century phenomenon safely should be easy to remember: 12312-2.
Without them, ultraviolet radiation will damage the eye's photoreceptors (cones and rods), while infrared energy will produce a direct thermal effect on the retina, causing solar retinopathy.
Symptoms of this condition, which may take time to appear, can include blurred vision, spots or scotomas at the point of greatest visual acuity, metamorphopsia (distorted perception of shapes) and reduced tolerance to light, or photophobia, which can lead to headaches.
The total phase of the eclipse will not last more than 1 minute and 48 seconds — the closer you are to the line of totality, the more seconds you will be able to enjoy the event — anywhere along its path across Spain.
