Something else began happening, too. As “Star Trek” went mainstream, its geeky universe grew less freaky and fun. This struck me especially during the 1986 release of the crowd-pleasing “Star Trek IV: The Voyage Home” and the hoopla over 1987’s “Star Trek: The Next Generation” TV series. Yes, we kooks were growing up. But things also became more commercial and less personal.

The change was palpable. At conventions, raucous trivia contests and showings of bootleg blooper reels evaporated. Unlicensed tribbles and tricorders, once sold openly, were now vended on the sly. No longer were you likely to snare a free signature from or impromptu snapshot with one of the stars. At last weekend’s Mission New York, the organizers announced, Mr. Shatner would command an “$80 Autograph Fee, $80 Solo Photo Op Fee.”

The fan base itself was hijacked by “official,” studio-backed organizations. In 1975, the authors of the book “Star Trek Lives!” estimated there were “hundreds — possibly even thousands — of fan clubs, small and large.” Did the fans really need the imprimatur of an “Official ‘Star Trek’ Fan Club,” run by Paramount Pictures?

In June, CBS and Paramount Pictures unveiled an extensive list of guidelines for anyone making an amateur “Star Trek” film. These included a $50,000 fund-raising cap, a time limit of 15 minutes on a “single self-contained story” (or two segments totaling 30 minutes) and no “depictions of drugs, alcohol, tobacco, or any harmful or illegal activity.”

Make no mistake: “Star Trek” continues to amaze and enlighten. After a poor start, “The Next Generation” won a devoted audience and critical acclaim. So did “Deep Space Nine,” “Star Trek Voyager” and other spinoffs. “Star Trek Discovery” will debut in January on CBS.

Still, my inner 12-year-old worries that this unique creation has lost much of its wide-eyed charm. Executed on a shoestring, begun amid major social tumult, “Star Trek” triumphed in large part because it tackled such essential and eternal themes as prejudice, war, learning and love. Shortly before the series began, the associate producer Robert H. Justman pleaded for “shows where the story is the thing and the gimmicks are unnecessary.”

Forty-seven years later I gaped when the U.S.S. Enterprise emerged, preposterously, from under water in the reported $190 million onslaught that was “Star Trek Into Darkness,” the second of three recent films. Recently, the original series’ casting director, Joseph D’Agosta, told me that he hated this summer’s “Star Trek Beyond.” “There was no heart or soul that Gene brought to the original series,” he said, “in story or character development.”

So this evening, exactly 50 years after America first tuned into “Star Trek,” I know how I’ll be celebrating. I’ll pop in my DVD of Season 1’s first episode, “The Man Trap,” a taut (total production cost: $185,401) thriller about a salt-sucking alien, mistaken identity and long-lost passion. I’ll pour a dram from my Saurian brandy bottle into my Saurian brandy glass. I’ll recite every line I can remember. And I’ll fondly call up a time when the cathode-ray tube dreams of a certain group of 20th century nerds soared skyward.