The sea has bottomless depths of mystery, but the sky rivals it in secrets. A cruise is the perfect place to learn about astronomy. Observing the night sky is so much easier when you’re at sea, away from artificial light. A number of cruise lines offer dedicated astronomy sailings; others have photography experts on board who can interpret the night sky.

The Canary Islands

The Canaries have the trade winds that prevent clouds from forming to thank for spectacular night skies. Three Starlight Reserves on the islands ensure the clarity of the night sky remains protected by laws relating to light, atmospheric and radio wave pollution, as well as flight patterns.

On Royal Caribbean’s 14-night Canaries Adventure from Southampton, two nights’ sailing from Cádiz to the islands offers a fantastic opportunity for constellation spotting. It also visits Tenerife’s Teide National Park, a designated Starlight destination.

From £1,399pp, departing June 29, 2019 (0844 493 4005; royalcaribbean.co.uk).

Africa

Lake Kariba, on the border between Zimbabwe and Zambia, is the world’s largest man-made lake and one of Africa’s best stargazing spots. A cruise on the lake is one of many highlights of CroisiEurope’s Southern Africa: Travel to the Ends of the Earth trip. It has plenty for landlubbers too, such as a safari in the remote Matusadona National Park.

There are dramatic skies above Lake Kariba Credit: iStock

Regent Seven Seas Cruises’ Cape Town to Rio de Janeiro cruise includes stops in Namibia, home to Africa’s First International Dark Sky Reserve and one of the world’s most sparsely populated countries, which means minimal light pollution. Views of the Milky Way and the Magellanic Clouds are particularly spectacular.

CroisiEurope’s nine-day cruise from Johannesburg, departing December 8, 2019, costs from £4,469pp (020 8328 1281; croisieurope.co.uk). Regent Seven Seas’ 14-night voyage, departing January 6, 2019, spends two days in Namibia. From £5,239pp (02380 682280; rssc.com).

Galapagos Islands

A new, luxury ship has landed in the Galapagos. Celebrity Flora has an innovative outward-facing design allowing 360-degree views of the islands. Expert-led ecological seminars and an open-air stargazing platform round out the experience.

Offering two seven-night itineraries, the ship first sets sail on May 26, 2019; from £7,599pp excluding flights, (0845 163 2337; celebritycruises.co.uk).

Antarctica

The cold, dry air above Antarctica is so still the light from distant stars is barely disrupted. A 20-day cruise with Mundy Adventures offers plenty of time for stargazing, plus a chance to see the total solar eclipse on December 4, 2021, from a remote spot in the Scotia Sea. The cruise also visits the Falklands.

Credit: Oceanwide Expeditions

Passengers sailing on National Geographic’s Journey to Antarctica cruises departing December 9 and 19, 2019, will be joined by photographer and film-maker Nick Cobbing, who will help you perfect your photos of the night sky.

The 20-day Polar Solar Eclipse cruise from Ushuaia, Argentina, costs from £16,735pp, departing November 25, 2021 (020 7399 7630; mundyadventures.co.uk).

The Atlantic

Out in the mid-Atlantic ships are thousands of miles from artificial light. If you plan to combine a transatlantic crossing with some stargazing, heed these tips: areas forward of the bridge are usually the darkest spots; avoid areas near brightly lit stairwells; and consider wind direction – you don’t want smoke from the stacks clouding your view. One of the best ships for transatlantic stargazing is Cunard’s QM2. Head to the on-board planetarium to learn more about the solar system, and sign up for talks on celestial navigation.

A seven-night westbound transatlantic crossing costs from £1,065pp, departing from Southampton on April 14, 2019 (0344 338 8650; cunard.co.uk).

The Arctic

Some of the night sky’s most exciting phenomena are best seen from inside the Arctic Circle. In winter, icy temperatures and near-constant darkness create the perfect conditions, although certain so-called circumpolar constellations, including the North Star, can be seen year-round. Seasonal constellations visible from the Arctic Circle include Cancer, or the crab, best viewed in early spring, and Pegasus and Andromeda in the autumn. Hurtigruten’s Astronomy Voyage includes a visit to the Northern Lights Planetarium in Tromsø.

The 12-day Astronomy Voyage from Bergen, Norway, costs from £1,610pp, departing November 20, 2019 (020 3131 6309; hurtigruten.co.uk).

Australasia

The southern sky has three of the brightest stars (Sirius, Canopus, and Alpha Centauri) and offers superb stargazing opportunities, including views of the Large and Small Magellanic Clouds – galaxies too far south to see from the northern hemisphere. Princess Cruises’ Australian Outback tour combines a 14-day cruise with six days on land. Short of time? Consider Royal Caribbean’s New Zealand cruise, which visits Milford Sound, 1,660 square miles of which is an International Dark Sky Reserve.

You could enjoy the skies in the Dark Sky Reserve areas of Milford Sound Credit: iStock

The 20-day Australian Outback tour from Auckland, departing December 30, 2019, costs from £3,899pp (0344 338 8663; princess.com). Royal Caribbean’s nine-night New Zealand cruise, from £1,139pp, departs Sydney on October 20, 2019 (0844 493 4005; royalcaribbean.co.uk).

Top tip

Patience isn't the only thing stargazers need a lot of – battery power is another, especially if you're using dedicated stargazing apps. For this reason, invest in a decent power bank, such as the Anker PowerCore 5000. Don't forget to pack decent gloves, either – ideally with extra grip to help you keep a tight hold on cameras and telescopes. North Face's Etip Gloves are designed to work with smart phones.