High up in the mountains, when the mist is lying low in the valleys, there are moments when men see angels.

Some have been spotted on the rocky outcrops of Fionn Bheinn, looking out towards the nearby Torridon giants.

Others, high up on the ridges of Ben Nevis, their silhouettes surrounded by rainbow halos of light, glowing in the haze.

In Germany, they're known as Brockengespenst, ethereal spectres on the Brocken, a peak in the Harz Mountains.

In Scotland, the mountain walkers call them Brocken spectres or mountain angels.

"The best times to see them is early morning or early evening," says Scots writer and hillwalker Alan Rowan.

"When mist is lying low in the valleys on a cold morning and there's a clear blue sky, you break through the clouds and the sun hits you.

"The light reflects off you on to the clouds below you and that's the figure you see."

A well known phenomenon to those like Alan who climb Scotland's peaks regularly, the spectres can seem enormous, a magnified shadow of the observer, cast upon the upper surfaces of clouds opposite the sun.

The head of the figure is often surrounded by glowing halo-like rings of coloured light that appear directly opposite the sun when sunlight meets a cloud of water droplets.

The ghostly figures can appear on any misty mountainside or cloud bank, of which Scotland has plenty.

They can even appear to move, sometimes suddenly, because of the shifting of the mist and variations in density within the cloud.

"Cold spring or autumn mornings give you a good chance of seeing them," says Alan.

"A lot of these things are down to luck as well. But if you're out a lot the chances of seeing something are higher."

Alan should know. This year alone he has completed 76 mountain climbs.

A writer, journalist and mountaineer, the 62-year-old grandfather has climbed the Munros three times and is currently halfway round a fourth circuit, the Furths and the Corbetts.

His first book, Moonwalker: Adventures of a Midnight Moutaineer, explained the beginning of his journey which he openly admits is an "obsession".

Composed out of ten years of notes and diaries he kept while traversing the hills and mountains of Scotland in the dark, Alan began his mountain forays by moonlight.

Working back shift as a reporter with the Daily Record, he would come off work at midnight and drive straight towards a mountain, climbing it alone by the lights of the stars.

Never much of a gym person, Alan's solution was not to go to sleep after his shift - but to head to the nearest mountain instead and greet the dawn.

Seeing the sun rise at 3000ft while the rest of the world slept on became an obsession for the talented sports writer.

His book about his adventures intrigued others even more.

Selling out in stores when it was first published in 2014, it made him a well-known name in the outdoors community, with Outlander star Sam Heughan among his fans.

His follow-up tale, A Mountain Before Breakfast published this year, promises to be just as successful - touchingly authentic and fittingly in tribute to his own friend Trevor who he lost to the mountains.

Trevor was joining a group of pals climbing Alan's favourite spot, Buchaille Etive Mhor, 12 years ago to mark his 50th birthday.

As a surprise, Trevor went up a day early to plant a bottle of champagne but died in the climb. It was a heartbreaking moment for the Alan and their group of climbing friends.

"After Trevor's death it split the club up a bit," says Alan.

"It brought in the danger of it, the seriousness. A lot of people expected me to chuck it, but why? Trevor wouldn't have."

Instead, Alan continued to climb and to introduce others to the beauty of the mountains.

His own granddaughter, six-year-old Ava, has walked with him, completing her first Scottish mountain this year.

"It was quite a gentle one and we went to see a fairy loch and a reindeer centre too that day," says Alan.

"She's intrigued by the idea of secret shelters too."

As are many. While there are several well known bothies in regions like the Cairngorms, there are also lesser known bolt holes that are an unspoken secret among regular mountaineers.

"It's a self imposed ban that no one will tell you about," laughs Alan.

"There's a place in the Cairngorms, a secret shelter, built years ago and almost impossible to find.

"I noticed a picture a decade ago and eventually found it. I go up there every so often - in fact I had my Christmas dinner there not so long ago."

Hidden out of sight on the other side of a cliff, the shelter is like a hobbit home, built into the rock with a small wooden door for an entry.

Inside, there are benches for sitting on, a plaque in memory of loved ones lost, an ornamental eagle and some candles.

"If you stumbled in there on a dark and stormy night at least you'd have a light," says Alan.

Bolt holes are a favourite past time and Alan knows of all the good ones.

"When you're in there lying on the floor, looking up at the crescent moon and stars, it's pretty good," he says.

Age is catching up with him slightly, Alan admits, not that it appears to have held him back all that much.

Ten years ago he was running around in the dark scouring out mountain paths by moonlight.

Today, he needs a head torch every now and then - a staple tool to everyone else, though to Alan it feels as though he's admitting to a massive indiscretion.

"Now my eyesight isn't as good," he says. "I got up at 4am for a climb with friends recently and wondered how on earth I used to manage."

Alan is modest. His adventurous spirit may not be as freshly ignited as it once was but it is most definitely burning brightly.

As he has got older, he is still chasing sunrises but has added in sunsets, too.

"I had this idea to try to catch the sunrise and sunset on the highest peak on every Scottish island," he says.

"I've found about 90 that I wanted to include for my next book.

"It's not about climbing mountains, merely the highest points I find, even a small hill that you have to push a cow out the way for to get the view."

Alan has already begun his quest and alongside his island hopping has pencilled in a couple of other books and some speaking events throughout 2017.

For a man who has felt the up draft from the wings of a golden eagle in flight, gliding so close he could see its eyes, and the rainbow glow of the spectres there surely cannot be that much left to see.

"I've never seen the Northern Lights," he says. "I've tried several times but never been lucky enough."

Though it's surely only a matter of a time. In a land of mountains, secret hobbit holes and misty angels, witne ssing the dancing lights of the aurora can't be far away.

You can keep up with Alan's mountain adventures and his books on his Munro Moonwalker website.