It was four in the afternoon, but my thoughts gravitated toward 6:30. That’s when the Sun and Moon would sit perfectly balanced on the seesaw of the sky. The full Moon would rise at 6:16; the Sun was slated to set at 6:47. For a few minutes, both would hang low above opposing horizons – an image best viewed well above sea level. We’d be viewing from 2,369 feet above it. Our goal: Mt. Diablo’s Eagle Peak.

But first we’d need to get there, and do it by means of good old-fashioned uphill trudging. No escalators, no aerial trams. As I waited for my hiking companions to arrive at the Donner Canyon trailhead, I wondered how they’d enjoy the trudge. To some, 7¼ miles is a short jaunt. Add 1,850 feet of elevation (the trailhead starts at 520’) along rocky, twisting stretches of trail and you get an entirely different equation – an equation serenaded by a chorus of huffing and puffing.

We wouldn’t be pampered at the peak, either. We’d be fully exposed to a 35 mph wind in 50-degree mercury, elements from which we’d be sheltered during our ascent. Not the ideal setting for kicking back around a campfire and chanting “Kumbayá.” I gave us 20 minutes – tops – before the shivering would set in.

And so I’d been wondering about the makeup of the group. My co-leader, Tony Salinaro, was the only known factor. Tony’s a Club One personal trainer and running guru – 60-plus and fitter than most 20-somethings. But what entourage had he assembled? Little did I know that it would include a 12-year-old boy and a woman four months pregnant – 10 adventurous souls in all, none of whom had ever assaulted Eagle Peak.

The evening could have been about the physical challenge, the aesthetic awe, the mountain’s visceral undertow – thrusting up from Earth’s innards; its mass dragging us down into the trail. The evening could have been about many things. What it became for me caught me by surprise.

Down toward the trailhead strode the group. Among the gifts they brought: Noelle brought her son Brandon (and her own Club One fitness director prowess), Mike brought Moon lore and a quick wit, Lizz brought the sense of awe and wonder she no doubt shares with her Timber Point second-graders, and Sandy brought soon-to-be Daisy (if “it’s a girl!”) in her womb. Then came Tony toting a backpack he’d never dream of bringing to one of his monster runs. And finally, Missy, Gloria, Michele and Christopher – the four who toughed it out to 2,100 feet above sea level and six miles but didn’t make it all the way. No trivial achievement.

It was 4:30. I said, “Let’s go.” Mike said, “Are we there yet?” and off we went on a rendezvous with Sun, Moon and mountain.

After a benevolent mile of level, wooded trail skirting Donner Creek, it came time to take the up-staircase. A half-mile of heavy breathing later and a few strides short of Meridian Ridge Road, Brandon spotted a tarantula that Tony and I had blithely breezed past, and the group took advantage of the photo-op. The tarantula, a male, was too fixated on his ritual autumnal cruise for chicks to even notice us. Score one for the paparazzi.

At the 1,300-foot mark we made the turn south at Meridian Point and faced a steeper foe: Meridian Ridge. Brandon, an Adams Middle School sixth-grader, considered the ridiculous incline a good opportunity to show everyone his smokin’ tail lights. I considered it a good opportunity to continue enjoying his company, so up we flew in tandem as Donner and Back Creek canyons fell away below us and Eagle Peak’s trapezoidal shadow took shape above us beneath a blinding Sun.

At Prospector’s Gap Road the group cut west to Murchio Gap, then traversed the bow-shaped ridge that connects the gap to the peak. At last, four miles and 1,850 vertical feet after our journey began, we planted our walking sticks on the apex of Eagle Peak. “Is this it?” pleaded Sandy. “I want this to be it!”

Yes, and what an “it” it was. To the west, a Sun trading gold for molten scarlet backlit Mt. Tam in Marin County and Sutro Tower on the San Francisco peninsula. In the foreground rippled the Berkeley Hills wreathed in the haze of dusk. We swung around to see the full Moon suspended low above Central Valley like a quartz pendant. For a while, Sun, Moon and the deepening world below distracted us from the wind raking Eagle’s naked summit. Gradually the blood circulation generated from the climb settled down, and so did we. We snapped our photos and ducked below the peak’s sheltering rocks. Time to reward ourselves with food and drink, time to inhale the intermingled aromas of tuna sandwiches and cranberry bars, Gatorade and black coffee.

And time to escape the wind’s brutal bluster. We hitched our packs for the narrow and craggy first leg of the descent as a last fleck of Sun flared behind the coastal range. The western sky became a bonfire shooting off the orange spark of Arcturus. To the south, Jupiter blazed blue-white above Diablo’s summit. As we swung away from the wind and hooked up with Eagle’s razor ridge, we caught sight of the Moon again, now searing white against the tide of black rising in the east. Behind us the horizon had cooled to a dying ember radiating a thin corona of crimson. Below spread Back Creek Canyon dusted in moonlight. Ahead and behind on Eagle Peak Trail, our fellow adventurers were dusted in moonlight, too.

Lizz was right. “Enchanting” captured the experience. But I’ll add one more modifier to the mix. The evening, you see, could have been about the physics, the aesthetics, the inscrutable power of the mountain. For an old trail tramp like me, accustomed to savoring these wonders in solitude, the evening of Saturday, Oct. 3 turned out to be about the camaraderie.

Thanks, everyone, for your incomparable company.