As this column goes to press, fans of the best sci-fi series on television are working to save the show from cancellation.

After four seasons, "Farscape" is ending, leaving the living spaceship Moya and her crew without resolution.

When it first aired on the Sci-Fi Channel in 1999, some viewers dismissed "Farscape" as "that show with the Muppets." (The Jim Henson Co. co-produces the series, and some of the aliens do have a slightly Muppet-like appearance.) But it quickly gained a devoted following and won praise from critics who appreciated the show's complex story lines, bizarre humor and fully developed characters.

For most hard-core SF fans, it was the best thing on TV since the early seasons of "Babylon 5," although I would argue that "Stargate: SG-1" is just as good.

But what TV executives care most about isn't quality. It's ratings.

These aren't the go-go '90s. The economy is sluggish. Advertising dollars are scarce. And cable-TV channels can't afford to produce as much original programming as they once could. (TNT once produced several original series; now it's all "Law & Order" all the time. Not that I'm complaining.)

When "Stargate: SG-1" jumped from Showtime to Sci-Fi, it joined "Farscape" on Friday nights to form the best two-hour block of SF programming on television.

During the last four months, "Stargate" averaged 1.32 million viewers per episode, with its audience share trending upward. But "Farscape," formerly Sci-Fi's ratings leader, saw its viewership fall to about 958,000 per episode.

"Farscape" creator Rockne O'Bannon and the Henson Co. appear to be moving on. According to Farscape.com, O'Bannon is writing a script for a "Farscape" movie, probably to resolve the fourth season's cliffhanger finale. And an animated "Farscape" spin-off series is in the works.

But "Farscape" fans are persistent. Since news of the show's cancellation broke late Friday, they have mounted an impressive campaign to reverse Sci-Fi's decision or persuade another channel to step in.

To join the effort, go to www.savefarscape.com or www.nebari.net.

Speaking of TNT, as I was a few paragraphs ago, another SF series got the ax last week.

According to TNT's promos, "Witchblade" was the hottest series on cable TV, but that didn't stop TNT from pulling the plug after two seasons.

Based on Image Comics' comic book and starring Yancy Butler, "Witchblade" is the story of a New York police detective, Sara Pezzini, who fights evil, both natural and supernatural, with the aid of a mystical weapon called the Witchblade.

Nobody at the network will confirm anything, of course, but the prevailing Internet rumor is that TNT canceled "Witchblade" because of Butler's widely publicized stay in an alcohol treatment center, which delayed production of the second season.

As with "Farscape," however, the real answer probably amounts to dollars and cents, or a lack thereof. Apart from made-for-cable movies, TNT has abandoned original programming in favor of network-TV reruns and later-in-the-week rebroadcasts of shows from its corporate sister station, The WB.

But "Witchblade" fans don't give up easy, either. A "Save 'Witchblade' " effort is underway at www.witchbladecentralstation.com.