Beginning at 8:30 their time last night, West Europeans watched live from San Francisco one of the most widely touted productions of the opera world this season-- the San Francisco Opera's smashing new production of Ponchielli's "La Gioconda."

And at the same time, but not at the same hour, the production was seen life here in Washington starting at 3:30 in the afternoon. In San Francisco, it was 12:30.

Thus San Francisco became the first company to broadcast live opera trans-Atlantic via satellite, a long-heralded prospect that may lead to a worldwide audience for televised opera and, once it becomes a profit-making enterprise, might provide a monetary boon for financially strapped companies everywhere.

On the whole, life trans-Atlantic opera could hardly have gotten off to a more advantageous start. Renata Scotto and Luciano Pavarotti were the stars, and both were singing their spectacular roles for the first time anywhere. The new production was about as opulent as any house could command today. And the visual effects were in the hands of those men who have polished their skills to such a fine point with the domestic "Live from Lincoln Center" telecasts, producer John Goberman and director Kirk Browning. It was they who brought us what is believed have been the most widely seen opera performance in history, the "La Boheme" broadcast from the Metropolitan that starred Scotto and Pavarotti.

Quite aside from the complexities of working in a house that is new to network television, the production was further complicated by having to send separate feeds, one with subtitles for North American audiences and another without for the Europeans.

Also it was broadcast for simultaneous FM transmission in stero. For Washingtonians, though, WETA-FM denied this needed dimension to the experience because someone else had already pinned down the necessary four hours on the local station. Someone there ought to rethink their priorities.

Just exactly what the long-term impact of this development may be for audiences and companies is uncertain. In an interview from San Francisco, Goberman pointed to the problems that time lags create for simultaneous transmission. "We could do this," he explained, "because the time lags just happened to fit. But even here the San Francisco Opera had to push back the opening time to make it right for Europe. And doing it from New York would be just that much harder. Meanwhile, the time differential going westward is so awkward that broadcasing live from Europe is out of the question. Anything would have to be taped here for later showing."

As to the immediate financial benefits, Goberman is even more sanguine. "Until we have pay cable TV, broadcasts are going to make very little for opera," he says. "But then I proposed 'Live from Lincoln Center' first as a cable proposal, and look where it has gone."