10 and 11 August are the ideal days to test your spot before the eclipse

On 29 April, the Sun occupied the same position in the sky it will hold during totality, and that day the dry run reported by the Catalan media took place. The eve of the eclipse meets the same astronomical condition again, with one advantage: if the spot you have chosen does not work, there is still time to change it. Here is the exact dry-run time for 33 municipalities, calculated from official IGN data.

On 12 August 2026, the Sun will go dark over Catalonia. But one circumstance shapes the whole observation: the Sun will be only about 4 degrees above the horizon, close to setting.

Four degrees is roughly the width of three fingers held at arm's length. At that altitude, any obstacle ruins the view. An industrial building 300 metres away. A row of poplars. A hill. A block of flats that does not even look tall.

That is why the relevant question is not "am I inside the path of totality?" but "is my horizon clear exactly where the Sun will be?". And that question can be answered in advance, with no instruments, using a basic astronomical calculation.

The basis: the symmetry of solar declination

The Sun's position in the sky at a given time depends on two things: the time of day and the date of the year. Over the year, solar declination — the height the Sun reaches — follows a cycle that is roughly symmetrical about the solstices.

That symmetry has a practical consequence: for any date there are other dates on which the Sun returns to the same position in the sky, though at a slightly different time. The time correction is not linear, because the equation of time — the difference between apparent and mean solar time — also comes into play and varies through the year.

Applied to the eclipse: if you identify a date on which the Sun reaches the same altitude and azimuth it will have during totality, you can go to your planned observation point, wait for the corresponding time and check on the ground exactly what you will see on 12 August — the only difference being that the Sun will be whole.

Where the calculation comes from

The calculation was made public in Catalonia by the Repte Experimenta project of the Universitat Rovira i Virgili, as part of the teaching material the URV produced for the eclipse.

The date that stuck in the region was 29 April. The astrophysicist and science communicator Joan Anton Català pointed it out publicly the day before, giving 20:21 as the reference time, and the Catalan media picked it up.

The origin is worth stating precisely, because this is not a generic institutional recommendation or a rule of thumb, but a direct application of celestial mechanics, verifiable with any ephemeris program.

The second window: 10 and 11 August

The annual symmetry works both ways. The days immediately before the eclipse meet the same condition with comparable precision.

On 11 August, the eve, the Sun sits about six tenths of a degree above the position it will hold during totality. That is a difference on the order of the Sun's own apparent diameter — half a degree — precise enough to reveal any relevant obstacle. On 10 August the difference is a little under one degree, still perfectly usable.

The August window also has a clear operational advantage over 29 April: if the dry run shows the chosen spot does not work, there are 24 to 48 hours left to find an alternative. Other August dates also help rule out obvious obstacles, but with less precision: on 1 August the Sun sits several degrees above the eclipse position.

The exact time in your municipality

The "Totality start" column comes from the official IGN tables. The dry-run columns are our own calculation: the time at which, on each date, the Sun returns to the position it will hold when totality begins. Tap your municipality's name to open its full page.

Times in local time (CEST). Totality start: official Instituto Geográfico Nacional data, referenced to each municipality's town hall coordinates. Dry-run times: eclipsi26.com's own calculation using solar ephemerides. Municipality pages are available in Spanish.

The dry-run times vary very little between municipalities: from the Ebre Delta to Lleida there is little more than one minute's difference. If your municipality is not in the table, a neighbouring one's time is valid.

How to run the test, step by step

The azimuth: a single value for all of Catalonia

The Sun's azimuth during totality is practically constant across the whole Catalan band. The IGN records 285° for the Lleida municipalities and 286° for those in Tarragona. Our calculations refine that range to between 285.4° and 286.1°: seven tenths of a degree across the extremes of the territory.

If the chosen spot does not work

First, and most important: look for alternatives within your own municipality before considering changing town. Most horizon problems are solved by moving a few hundred metres.

Planning tools

Some apps complement the on-the-ground dry run, especially useful if you plan to photograph the eclipse. PhotoPills (iOS and Android) is the reference among photographers: enable the Eclipses layer, drop the pin at your spot, set the time bar to 12 August 2026 and use the AR button to see the Sun's exact position overlaid on the camera. Under "More > Horizon" it calculates the horizon with terrain relief.

Free alternatives: Stellarium Mobile (a full planetarium, the one recommended by the official eclipse site), Sun Surveyor Lite and PeakFinder for horizons with relief. None replaces the dry run: at 4 degrees altitude, the margin of error of a phone's sensors is comparable to the size of the phenomenon itself. The app orients you; the dry run confirms.

Eye protection

Keep the memory, not just the photo

Anyone who bothers to go to the observation point on 10 or 11 August, measure the horizon and decide where they will stand is exactly the person who will want to keep what happens on the 12th. Phone photos end up lost among thousands of files. A physical object does not.

Family keepsake · Limited edition · ISBN 978-84-09-88106-2

Family Keepsake Book
of the 2026 Eclipse

72 full-colour pages. Science, mythology, natural history and the effects of the eclipse on animals, seas and people. A guide-book and family diary where the memory is written down just as it happened: the spot you chose, the time, who was there, what you felt. A physical place to return to as many times as you like in the years ahead. (Spanish-language edition.)

✦Illustrated scientific eclipse content

✦Pages to record your own experience

✦Photo collage of eclipse day

✦Physical keepsake reliquary

✦Original illustrations

✦Free shipping within Spain

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