It was not exactly a perfect night in Washington for Fourth of July fireworks this year, when fog and rain blanketed the sky and made the Independence Day show from the National Mall less impressive than usual to those who had staked out a spot nearby.

But if you had tuned in on Monday to watch the fireworks on PBS or watched it on your cellphone, you might have figured the sky was cloudless and the fireworks were crystal clear. You might also have wondered if someone had removed the scaffolding that has been on the Capitol dome for two years.

But many eagle-eyed viewers suspected something was not quite right, and PBS later admitted as much: It had spliced in firework footage from previous years with live shots.