What is the best time to stargaze tonight?

Go out after astronomical twilight has ended, at a time when the Moon is below the horizon or only a thin crescent, on a night with little cloud and dry air. Those three things, darkness, Moon and weather, decide more than the hour on the clock.

I build Sky Map, the app mentioned below, so weigh my suggestions with that in mind.

1. Wait for real darkness

After sunset the sky goes through stages of twilight. It only becomes fully dark at the end of astronomical twilight, when the Sun is 18 degrees below the horizon. Depending on where you live and the season, that can be an hour and a half or more after sunset, and in high-latitude summers it may never happen at all. Bright planets and stars are visible earlier, so you can start then and save faint targets for later.

2. Check where the Moon is

The Moon is the biggest light source in the night sky. A bright Moon washes out the Milky Way and faint meteors. It rises later each day, so a few days after full Moon you may get dark early evenings before it comes up. The week around new Moon gives the darkest nights. For the Moon itself or for planets, its phase hardly matters.

3. Look at clouds and humidity

Thin cloud you barely notice in daylight hides a lot at night. High humidity adds haze that dims stars near the horizon. Clear, dry nights, often after a weather front has passed, show the most.

A two-minute check before you go

1. Find out when astronomical twilight ends tonight.
2. Check the Moon’s phase and when it rises and sets.
3. Look at cloud cover and humidity for the evening.
4. Give your eyes 20 to 30 minutes outside before judging what you can see.

Where an app helps

Sky Map has Tonight’s Sky Conditions, which shows cloud cover, humidity and the best time to look. The planet visibility timeline shows which planets are up and when, and the astronomical calendar lists meteor showers, eclipses and other events. The core sky map works without internet. Sky Map is free to download, the AR view is free, and some features are paid.

Read next: dark adaptation with a phone in hand, stargazing in the city and meteor showers, the Moon and eclipses.