Menorca sits inside the path of totality, but the geometry is extreme
and it drives every decision in the plan: the Sun is 2 degrees above
the horizon at maximum, on azimuth 288, and totality lasts 1 minute
12 seconds at Ciutadella before the Sun sets at 20:42.
Two consequences follow from that 2 degrees. The light travels through
roughly twenty times more atmosphere than at the zenith, so everything
is dimmer, softer and redder than any published exposure table assumes
and the histogram has to be the authority rather than a chart. And a low
hill, a building or a haze bank on the sea horizon hides the entire
event, so an unobstructed west-north-west view matters more than
anything else about the site.
That produces a genuine trade-off worth recording. Totality runs 1m38s
at Mahon against 1m12s at Ciutadella, because the centre line favours
the south-east - but Mahon is on the east coast, so from there the view
towards 288 degrees crosses the island with Monte Toro in roughly that
direction. Horizon beats duration: 26 extra seconds is a bonus, a
blocked horizon is total loss. The plan therefore recommends a west or
south-west coastal site.
The plan also corrects an idea that was on the table: a photographic ND
filter is not a solar filter. Standard NDs cut visible light while
passing infrared largely unattenuated, which is where the heat is, and
that will damage a sensor. The requirement is a certified ISO 12312-2
filter around OD 5 on the front of the lens, with the specific warning
that Baader's AstroSolar Photo Film ND 3.8 is camera-only and unsafe to
look through, while the ND 5.0 safety film does both jobs.
The Star Adventurer GTi is explicitly excluded from eclipse day.
Seventy-two seconds needs no tracking, and polar aligning in bright
twilight towards a 2 degree Sun is impractical. It earns its place on
the night skies of the same trip, not on the 12th.
Kept in this repo rather than in a notes app because it is worked out
from real numbers, it will be revised as the date approaches, and the
reasoning behind each decision is the part worth keeping.
laurence
653ca103cd