Before anything else, find out how dark your sky actually is. The Bortle scale runs 1 to 9: 1 a genuinely excellent dark site, 3 rural, 4 the rural/suburban transition, 5 suburban, 7 suburban/urban, 9 inner city. Each class up costs you roughly half a magnitude of your faintest visible star — and because the scale is logarithmic, half a magnitude is 37% of the light gone. This is a Bortle 5 sky, which is what most people reading this actually have.
Bortle 8, city. Your limit is around magnitude 4.0 — a few hundred stars in the whole sky, and the Milky Way is a rumour. But notice what survives:
Vega,
Altair and
Deneb are all still there, because a first-magnitude star does not care about your postcode. City astronomy is real astronomy; it is just a different target list. Double stars, the Moon, and the planets are barely affected at all.
Bortle 3, rural — the same patch of sky. Limit around magnitude 6.5, roughly nine thousand stars over the whole sphere, and the Milky Way shows structure. Getting here is usually a 30–60 minute drive, not a plane ticket: light pollution falls off steeply outside a city's edge, and two Bortle classes is a common return on an hour in the car. Check a light-pollution atlas before you pick a spot; do not trust the map of where the roads are.
Then dark-adapt, because the other half of the problem is your eyes. Pupils widen in a couple of minutes, but the chemistry is slow: rhodopsin takes
20–30 minutes to regenerate and continues improving for an hour, and the difference between minute one and minute thirty is roughly
two magnitudes. One glance at a white phone screen undoes most of it. Use a dim red light, and if you must check your phone, close one eye.
Now navigate. Never start from a faint target — start from one shape you are certain of and hop outward. Tonight that is the
Summer Triangle; in winter it is Orion; year-round in the north it is the Big Dipper. Learning three of these covers the whole sky, because everything else can be reached from one of them in two or three hops.
Face south. Everything that rises crosses the meridian here, and the meridian is where it is highest, which is where you are looking through the least air. The arithmetic is unforgiving: at 60° altitude you look through 1.15 atmospheres, at 30° through
2.0, at 20° through
2.9 — and each extra atmosphere costs about 0.3 magnitudes to haze. Observe a target within an hour or two of its transit or do not bother.
Face east to plan the rest of the night. Everything on this side is on its way up, at
15° per hour: something clearing the horizon now will be 45° high in three hours and crossing the south in six. That is how you sequence a session — the western targets first because they are leaving, the eastern ones last because they are still climbing into good air.
Face north for the stars that never leave. The circumpolar cap — the Big Dipper, Cassiopeia, Cepheus — is available every clear night of the year, which makes it the right place to practise. And read the altitude on
Polaris: that number is
your latitude, wherever you happen to be standing. Change the location on this page and watch it follow you. A star that doubles as a sextant is worth ten minutes of your attention.
Last check before you commit to a date: where is the Moon? A full Moon raises the sky brightness by three or four magnitudes per square arcsecond and turns a Bortle 3 site into a Bortle 6 one — galaxies and nebulae are simply gone. This is the Moon at tonight's instant, with its altitude and the time; if the number is negative you have a dark sky and should go. The usable window for faint objects is roughly the week either side of new Moon, and the rest of the month belongs to the Moon itself, double stars and the planets, which do not care.