Move over Karl the Fog. Here comes Carl the Dob

Astronomer Brian Castro and his Dobsonian telescope are turning Valencia St. into stargazing center

At Burning Man in Nevada’s Black Rock Desert, Brian Castro and his camp set up a telescope twice the size of the one he’s now using to showcase the sky in the Mission District. Dwarfed by Nevada’s abounding desertscape, the larger scope, with a 20-inch diameter mirror, requires a ladder attachment to view. Attendees often are “enhanced,” says Castro, and lasers dance across the night as the burning men gaze into the scope’s aperture.

“People’s views looking at Saturn are always good. But add something else in there … that’s like a religious experience,” he says.

Things are slightly less stimulated on 18th and Valencia streets where Castro has been offering up views from his Sky-Watcher Flextube 250P Collapsible Dobsonian the past few moon phases. Even so, the scope garners a consistent stream of onlookers. People moth to its denture white and eternal void black frame. People stroll by, first curious about the crowd and then hooked when they read “FREE” on his chalk sign.

“It’s pretty” is Castro’s first answer when asked what he appreciates about the night sky. “And, I find it somewhat beautiful that we are tiny specks on a speck among billions of billions of specks. And our entire lifetime is just a flash of an instant in the history of the Earth.”

Castro first developed his ardor for stargazing when he was an undergraduate student at University of Rochester. He worked at the university’s observatory from 2011 to 2013, then as an astronomy intern at Bryce Canyon National Park in Utah in a role similar to the one he has now adopted as a sidewalk astronomer. (This is a side gig to his day job as a programmer at Orbital Sidekick, a startup focused on satellite imagery.)

The amateur astronomer is an avid admirer of the renowned astro-pioneer and science communicator Carl Sagan. Sagan once claimed, “We are all made of star stuff,” an idea that has propelled Castro forward in his appreciation of the ether.

“Our stars and our planets were formed out of the guts of exploded stars 5 to 10 billion years ago or something. So … everything you see around you was forged inside of a star billions of years ago.”

And when we, beings made of cosmos, contemplate the cosmos — “it’s almost kind of metaphysical,” he says. “Humans are a way in which the universe can understand itself.”

When he moved to the Bay Area seven years ago, Castro volunteered with the Planetary Society, a nonprofit founded by Sagan and now run by Bill Nye “the Science Guy.” Much like his evenings on Valencia, Castro’s work with the society was centered around sidewalk astronomy, a practice first popularized by John Dobson on the streets of San Francisco around 1968 when he founded a club in The City dedicated to the activity. The “Dobsonian” model denotes the use of low-cost materials and was developed by Dobson who, according to the Sky-Watcher site, “literally wrote the book on how and why to make amateur telescopes.”

Dobson’s astronomic outreach made space social and accessible — which, for Castro, is much of the appeal. “Primarily I enjoy (astronomy) with other people. I enjoy sharing it and just talking to people about it.”

Parts of Valencia Street, including the corridor between 18th and 19th streets, are closed to traffic on weekends, which opens it to telescopes and pedestrians alike and allows Castro to circumvent buildings that may impede his view.

We aren’t taking enough time to appreciate the night sky, Castro insists. He recalls an evening in Bryce Canyon when he was able to bike home by the light of the Milky Way.

But even in The City, it’s worth stopping to look.

The most beautiful things to look at, in my opinion, are the moon, Jupiter and Saturn. And you can see all three of those just as well in downtown San Francisco as you can see them in the middle of the Sahara desert,” he says.

A sidewalk astronomer’s skill lies in his ability to make the beyond feel approachable and engaging to the average Earthling. The ever-distant planets, nebulous formations and frothy star scatterings can be cause for overwhelm as much as intrigue — especially if you were just wandering your way to the nearest burrito joint, only to be lulled in by the gasps of other star-struck Missionites.

Castro navigates the skies with a stellar grace. “And it’s one of the few things in life that … I want to be modest here, but I feel like it was just something I was kind of naturally good at,” he says.

But it wasn’t until the pandemic hit that Castro decided to prioritize his passion. He’d had crappy telescopes before, or ones borrowed from friends, but never one that he could lug across town and use to shepherd San Franciscans through the starry skies above at his whim. Upon returning from a short escape to Washington’s Olympic Peninsula in summer 2021, he found a place in the Mission and bought himself a Sky-Watcher.

Now, he sticks to a quasi-schedule, revolving around three key criteria: a clear sky, a clear schedule and something worth looking at. The planets come out in August and, until then, he’s loosely adhering to the moon’s first quarter — the week or so following a new moon — because that’s when she’s at her best.

If you’re curious, the best way to locate Castro is through his Instagram or Twitter account @carlthedob, named for the men who inspired his starry pastime — and never to be confused with its nemesis, Karl the Fog.

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