'The moon's all splodgy." Our road-trip to admire the constellations above La Palma should have been an enlightening one. After all, this is the place where, way back in 1988, the Spanish government enacted legislation to protect the night skies. No industry above 1,500m is allowed on the steep sides of this tiny Canary Island; street lights glow orange rather than white at night; electro-magnetic interference is strictly controlled. The edict even extends to the north coast of neighbouring Tenerife, which is visible from the eastern shores of La Palma and a potential nuisance when it comes to light emissions.
The reason for all this? A huddle of star-gazing scientists who lurk with their telescopes near the rim of the Caldera de Taburiente, the huge crater that dominates the island. They're trying to discover the secrets of the universe, you see. And for that they need dark. Lots of dark.
But dark wasn't our problem. The Spanish government has other things to worry about these days, and heavy clouds in the Canaries may well be beyond its remit. Nevertheless, inclement weather can be a blight for amateur astronomers. Two evenings of phone conversations with a very patient Carmelo González Rodríguez from local company Astrotour had elicited the same response: there was no point venturing out with a telescope.
"It is difficult to predict, particularly at this time of year," said Carmelo. If he'd been an astrologer rather than an astronomer, he'd probably have suggested that our stars weren't quite in alignment.
Neither fate nor fact was enough to deter us. That night, in the hope that meteorological conditions would improve, I drove my family westwards from the seaside resort of Los Cancajos to the isolated Llano del Jablo viewpoint, high above the small town of El Paso. Upon arrival – and having disturbed an amorous couple who drove their steamed-up Renault away in rather a hurry – we discovered a sign pointing to Polaris (431 light years away) and a curious wooden wheel which could be rotated to confirm the names of the constellations, had they been visible. Sadly Carmelo's advice proved accurate. White cloud obscured the Milky Way. Even the moon was, as my six-year-old son pointed out, splodgy.
One of the challenges La Palma faces as a tourist destination is that very little, including the skies above, is laid out for you on a plate. Benign weather is the reason many families visit the Canary Islands, and last year the prospect of year-round sunshine drew 1.44 million British holidaymakers to Tenerife, the largest island in the archipelago. La Palma, a third of Tenerife's size, pulled in just 1 per cent of that total, a mere 14,876 UK visitors.
La Palma's relatively high rainfall delivers an alluringly verdant landscape, but it no doubt plays a part in the island's isolation from mass-market tourism. As does the island's imposing topography. It's one of the steepest in the world, the northern half jutting fiercely from the Atlantic. The route from the capital, Santa Cruz, along the LP-4 road to the Institute of Astrophysics observatory (see panel) and beyond to the island's highest point, the epic Roque de los Muchachos (2,423m), is dramatic. It passes through pine forest and lava fields on its journey above the clouds. But it's also tortuous: a tightly knotted ribbon of hairpin bends and switchbacks.
In La Palma you won't find the tourist-friendly beaches of Tenerife's Playa de las Americas and Los Cristianos, dressed in imported white sand. Instead, the sand here is volcanic and black – which can provide an alarming contrast if you've neglected your tan. There's no equivalent of thrill-a-minute water parks, no soothingly chic spa complexes. The majority of the coastal real estate is given over to banana plantations rather than hotels. Four-fifths of La Palma's income comes from the crop, the plants themselves corralled behind walls and within polythene tents like hungry Triffids.
But, of course, these are all reasons to visit La Palma, rather than stay away. A visit here is, literally, a chance to be one in a hundred, rather than one of the multitude.
Los Cancajos is a tidy if unremarkable throng of apartments and aparthotels that lies just south of Santa Cruz. It's the only substantial tourist town on the east coast (La Palma's sole all-inclusive complex, The Princess, is tucked away down on the south-west shore). The resort contains a few restaurants and shops and a fine stretch of beach. Here cube-like blocks of black concrete have been placed alongside the lava as shelter from Atlantic swells – as if the organic shapes of the coast have given way to a parallel, pixelated version.
It was immediately clear that a lack of water parks would be no deterrent to the children's enjoyment of La Palma. An afternoon spent building black sandcastles was followed by a snorkelling session in an Atlantic Ocean that was still relatively warm even at the beginning of November.
Our hotel, the Hacienda San Jorge, possessed the pre-eminent position in Los Cancajos, its back door leading straight to the beach. Inside, it was arranged around four sides of a tropical garden that contained exotic flora, including a couple of examples of the Canary Islands' iconic Dragon Trees which looked disarmingly like huge loo-brushes.
The rooms here – comfortable rather than stylish – each come with a balcony and have tiny kitchens for those intent on self-catering. Alternatively, copious buffet dinners are offered in the long dining room, or under the shade of a huge rubber tree (ficus elastica according to one of the handy botanical plaques), with views of the salt-water swimming pool. The pink and yellow buildings are pleasantly low-rise and low-key, the staff enormously friendly and obliging – and the clientèle is made up almost exclusively of German hikers.
Hiking is La Palma's big secret. Or at least it's a big secret from everyone except the Germans. The entire island was declared a World Biosphere Reserve in 2002, offering protection to areas including pine forest, myrtle heath, lava fields and the striking rock formations of the Caldera de Taburiente itself.
More than 1,000km of marked trails run through these wildly varying landscapes, the majority comprising challenging treks through the mountainous interior. Many require either the services of a guide or a taxi to get you back to your starting point (various "taxi stops" are marked throughout the island, so that you can arrange a ride home).
Perhaps the most striking terrain of all is the Bosque de Los Tiles in the north-east, a primeval strip of ancient laurel forest positioned at just the point where the trade winds dump their moisture on the island. Heavy with damp, dark undergrowth and set round a series of deep ravines, it's the sort of place where dinosaurs probably still roam, ploughing through the greenery and quietly digesting tourists. The perfect place for a brisk walk, I thought.
The best-known trek here is the walk to the Marcos and Cordero springs which, for reasons that later became clear, begins with a taxi ride. Slightly resentfully, I handed over €60 to a cigar-chomping driver at the visitor centre, so that the four of us could cram into the back of his ancient 4x4 minivan alongside a Spanish and German couple.
I assumed, naively, that we'd be in for a brief trip up a hill, from where we would potter back down through the rainforest. Fifty minutes later, having jostled our way over the steepest, most pot-holed track I have ever endured, we reached the starting point for our walk. In the process our driver had virtually expired in fit of hawking, snorting and violent expectoration, while his vehicle had fared little better. Our children, meanwhile, had fallen asleep on the back seat, lulled by all the furious juddering. Sixty euros well spent.
The journey through Los Tiles is exhilarating and exhausting in almost equal measure. It starts right among the clouds, passing beside the tiny channel of water that runs from the mountain springs. Then it takes in a series of 12 head-height, pitch-black, damp tunnels (bring a torch) before hikers are required to clamber and crouch their way through a final water-filled conduit at the base of a cascade. It's all quite an adventurous undertaking when you're travelling with a six-year-old and his nine-year-old brother.
Finally, you trek down the side of a ravine, along an empty river bed filled with boulders and back through a narrow valley of vast ferns and slender laurel branches. The last viewpoint at Topo de las Barandas is like a still from Jurassic Park: a basin of limitless green. It's not family friendly – the hike took us five hours and we arrived back hot, wet and hungry – but it's certainly exciting.
Of course, no one wants to be intrepid every day. We spent happy hours at La Fajana Piscinas in the north of the island, where low-lying lava has been tastefully enhanced with concrete to construct sheltered pools fed by the Atlantic Ocean. At high tide it's an unnerving place to swim, as waves crash over the low barriers. The pools at Charco Azul, just to the south, are arguably even more picturesque, hemmed by phalanxes of banana plants.
Near El Pilar, we came across Acropark, a high-ropes course which had opened just a week earlier, tucked among pine trees. There were no other guests when we visited, so the boys were allowed to scamper around it twice, immediately becoming experts at using the life-preserving carabiner.
Close by, a visitor centre marks the beginning of one of the greatest hikes on the island, the Ruta de los Volcánes (Volcano Route). This runs down the island's centre to the southern tip, a march across a crater-strewn landscape that was far beyond our capabilities. Instead we attempted our own mini-version. We drove south to Fuencaliente and took a walk along the rim of the Volcá* San Antonio, the interior of which was prickled with young pines.
Urged on by our children, we then mounted Marina and Celia, two local camels, who conveyed us all to a viewpoint overlooking the impressive Volcá* Teneguía, which lies just to the south. In 1971, Teneguía was the scene of La Palma's last eruption, as the volcano sent streams of lava down towards the coast, adding a few extra acres of banana-friendly terrain to the island's outline in the process.
We even managed a dose of civilisation, buying €1.30 bus tickets for the 15-minute journey from Los Canjacos to Santa Cruz. Here a pedestrianised, cobbled main street runs past smart shops, and slender alleyways reveal glimpses of the ocean. Despite being the capital city, Santa Cruz is a modest sort of place, its pleasant colonial core defended from urban sprawl by the volcanic crater that rises behind the steeply-raked streets.
But something drew us back to La Palma's heart. From the national park visitor centre, the road winds upwards to the Mirador de la Cumbrecita, a saddle of land overlooking the 8km-wide indentation of the Caldera de Taburiente.
From here, an hour-long walk to the viewpoints of Los Roques and Lomo de las Chozas reveals a lost world shielded by rock walls and vivid with the bright green of Canarian pines, a plunging scoop so vast that it traps its own clouds.
We visited twice, once at the beginning of our stay and once at the end, striding along forest paths coated in pine needles, the views of the Caldera spread out below us.
As for our attempt to see the rest of the universe, in the end there was no need for that night-time drive across La Palma. The skies finally cleared at around midnight – and from the balcony of the Hacienda San Jorge, I looked up to see a cloudless sky glittering with light. Our stars had finally aligned.
Eye on the sky :The largest telescope in the world
La Palma's Observatorio del Roque de los Muchachos is set far above the cloud layer at 2,369m, close to the highest point on La Palma. The site was chosen because the Canary Islands lie in a dark part of the world, far from major cities, and La Palma's position at 28 degrees north of the Equator means that astronomers can view all of the northern hemisphere stars and many of those in the southern hemisphere.
Rather than being housed in one observatory, the telescopes are all separate, jostling for position on the mountain. Each has its own building, and is operated by its own European country. Britain runs a collection of three, known as the Isaac Newton Group (ING), with international astronomers allowed access to the facilities according to the importance of their research.
At 4.2m in diameter, the William Herschel Telescope (WHT) is the largest of Britain's telescopes; indeed when it was built in 1987 it was the third-largest in the world. However, the WHT is now dwarfed by the adjacent Gran Telescopio Canarias (GTC), Spain's 10.4m-wide behemoth that began operation in 2007 and now rejoices in the title of the largest single-aperture optical telescope in the world.
Budding star-gazers may be intrigued by the news that last month ING (ing.iac.es) announced that its smallest telescope, the 1m-wide Jacobus Kapteyn would be "made available free of charge to a suitable party interested in taking control of the scientific exploitation of the telescope". It's not for fun, though: "The new owners will preferably be a recognised public research or training organisation, and will be expected to use the JKT for astronomical research."
Free guided visits around the observatory are offered year-round. Visitors are given access to one or two telescopes, depending on availability. Children under 12 cannot visit the GTC. A minimum of two weeks' notice is required to arrange a tour. See iac.es for more information.
Travel essentials: La Palma
* Thomson Airways (0871 231 4787; thomsonfly.com) flies weekly from Manchester and Gatwick to La Palma.
* Thomson (0871 231 5595; thomson.com) offers seven nights half-board at the Hacienda San Jorge from £543 per person (based on two sharing), including flights and transfers.
* Holiday autos (0871 472 5229; holidayautos.co.uk) offers a week's car hire from £90.
* Astrotour (00 34 616 377 227; astrotour.es) offers a range of tailor-made astronomy tours.
* Acropark (00 34 674 193 628; acropark.es). Admission is €18 (€6.50 for children).
* Car-parking spaces at the Mirador de la Cumbrecita must be booked (for free) at reservasparquesnacionales.es