Every athlete dreams of a moment of ultimate glory. Few live it. Tonight, with one perfect swing, one that he labeled lucky, Alan Ashby lived the impossible dream.

Eight years a journeyman catcher, a career .232 hitter, Ashby hit a two-out, two-run homer in the ninth inning tonight, giving the Houston Astros a dramatic 3-1 victory over the Los Angeles Dodgers in the opener of the National League West playoffs.

"I feel just like Walter Mitty," Ashby said after hitting Dave Stewart's fast ball deep into the right field seats. "I've always dreamed of a moment like this one. I have to admit I went up there thinking about a home run. I know that sounds silly coming from a guy who hit four home runs, but I just felt I could do it.

"I just got a fast ball down the middle knee high, a ball I could swing at. As soon as I saw it in the air, I just knew it was going to creep out of here. I was jumping up and down almost as soon as I got out of the batter's box."

Ashby was mobbed at the plate and the Astrodome crowd of 44,386 demanded two curtain calls. His heroics made a winner of Nolan Ryan, who pitched a masterful two-hitter, retiring 20 of the last 21 batters he faced.

"Great feeling to see that ball go out," Ryan said. "I think that's the first time we've won a game in the bottom of the ninth since I've been over here. I hope it will give us some momentum."

If the Astros have momentum, much of it will be because Ryan, their ace, outdueled rookie Fernando Valenzuela.

Like Ryan, Valenzuela was superb tonight. He gave up only one run on six hits before being lifted for a pinch hitter.

"I never thought about leaving Fernando in after the bottom of the eighth," said Dodger Manager Tommy Lasorda. "He had pitched hard and he had pitched well. The pinch hitter (Jay Johnstone) was our leadoff hitter in the ninth and I have faith in our bullpen."

Stewart, 24, has done well this year, posting a 2.57 ERA. He got the first two hitters in the ninth, then Astro Manager Bill Virdon sent Craig Reynolds up to pinch hit for shortstop Kiko Garcia.

"I just wanted a left-hander to hit against him," Virdon said. "If we didn't score, I didn't want to have wasted a pinch hitter and I knew Craig would go in at short for Kiko."

Reynolds singled up the middle. That brought up Ashby, who had been zero for two against Valenzuela. Ashby, a switch hitter, was hitting lefty the first time tonight.

"I just wanted to start with a fast ball, try to get ahead," Stewart said. "But I grooved it a little." From the moment the ball left Ashby's bat, the only question was: would it stay fair? It did, by several feet, and the Astros led the three-of-five series.

"It's still only one game and if we win tomorrow (Wednesday at 1:05 p.m.), we're still in real good shape," said Dodger Steve Garvey, who turned Ryan's only mistake into a seventh-inning home run.

Pressure games in this dome produce special baseball. Last year in the NL championship series, the Philadelphia Phillies and Astros played three extra-inning epics. Tonight, these two teams continued the dramatic trend.

The game had been billed as a pitching duel between Ryan, the National League's ERA leader (1.39) and Valenzuela, baseball's darling of the spring who pitched well but in hard luck during September.

The game lived up to its hype. Ryan had no-hit the Dodgers here 10 days ago, but tonight the Dodgers' second batter, Ken Landreaux, singled cleanly to center. That hit and Garvey's home run were the Dodgers' only offense tonight.

Valenzuela was almost as good. For five innings he matched Ryan, giving up two scratch hits. But in the sixth, Terry Puhl singled with two outs and Phil Garner walked. Tony Scott then hit a blooper to right center.

Lopes, Landreaux and Rick Monday all charged the ball. Lopes caught up with it. But he misjudged it, pulling his glove toward his body, rather than extending it. The ball dropped and the Astros led, 1-0.

Garvey got the Dodgers even in the next inning. "I just out-thought myself," Ryan said. "I had started the first two guys with curves and I thought Steve would be looking for another one. I threw a fast ball,

"Overall though, I felt I was in command. My curve and my control were sharper than in the no-hitter."

The 10th inning would have been Ryan's last, Virdon said. But Ashby solved that problem.

"I grew up in San Pedro idolizing the Dodgers," Ashby said. "Just playing against them is special for me. Having this happen is unreal."