Doubtful - Endor was on the other side of the galaxy.
I’m mixing my Death Stars here. Regardless, blowing up Yavin would presumably destroy both the moon with the rebel base and the Death Star; after all, both the Death Star and the moon are in orbit around Yavin. It’s been a couple years since I’ve seen it, but what I recall is that the Death Star needs to wait until the fourth moon appears over Yavin’s horizon. That implies that both the Death Star and the moon are not that far away from Yavin, and blowing up the planet would deal comparable damage to the Death Star.
“Oh, so we are rationing laser bolts now?”
“Do *you *do the budget, Terry? Do you?”
And we al know how Imperial Marksmen stand up to the broad side of a barn.
It wasn’t just made to destroy inhabited planets; it was made to destroy shielded inhabited planets that could withstand fleets of Star Destroyers; and as we saw with Alderaan, it had plenty of overkill even for that. I’d expect the result when it hit a gas giant to be pretty impressive. But in their eyes they just had no reason to hurry.
As for the Death Star II, it was much larger and more powerful; it had a much faster recharge time. Probably at least in part to ensure that the Yavin situation didn’t reoccur.
Come on, how much of the force of an energy blast like that do you really think planet-wide shields can absorb or deflect? Maybe Alderaan took twice or three times as much energy to explode as an uninhabited and undefended planet of the same mass.
Jupiter is 317.8 times the mass of the Earth. There is that much more matter within in that can absorb energy, and also a correspondingly steeper gravity well for any of it to fly out of if you want an actually explosive effect. And unlike with a rocky world, there wouldn’t be much of a noticeable tactical effect if you COULDN’T explode it - even if you raised the temperature of all the atmospheric layers, that wouldn’t hurt the moon, and it wouldn’t let you fly the Death Star through the place where Yavin was, because it’s still there.
I’d go so far as saying that there might be one kind of impressive result if the Death Star shot at Yavin - a localized gas eruption, something a bit like a solar flare except not from a sun. However, that would shoot out from the side of the planet where it was struck, and therefore would be more of a danger to the Death Star itself than to Yavin 4, if the Death Star wasn’t already in range for a direct shot.
“What do we get paid by the laser!?”
I love how people try to apply science to Star Wars. Just push that rock up the hill one more time, guys.
Star Wars ships have those big main engines for main STL thrust, but they meneuver and hover using invisible “repulsorlift” technology. I suspect the Death Star mostly just hyperdrives into orbit and lets gravity do the rest though.
It didn’t just “explode”, it exploded violent and dramatically with far more force than necessary to destroy it. So yes, I thing the result when hitting a gas giant would be spectacular and probably fatal for anything near in astronomical terms.
As I recall, the calculations for how powerful the beam must be to blow up a terrestrial planet like Alderaan so violently imply that you’d be putting more energy into the planet than the Sun’s total output. So I expect it would flare bright enough to boil off the surface of a moon orbiting it, at the very least. It might well go up like a gigantic fusion bomb.
All these worlds are yours, except Yavin IV?
Well, we have other case history to suggest that “Knowing where best to come out of hyperspace” is not considered a critical part of Imperial Officer training.
Paperwork. There are a shitload of reports and environmental impact statements to file if you destroy a planet. But a moon can be destroyed without any of that bother.
Flying through hyperspace isn’t like dusting crops, boy.
Best quote of the movie, considering the Stormtroopers’ lack of ability to shoot Han, Luke, Leia, or Chewie. 
Makes you wonder how incompetent the sand people must be. I figure they must be batting about 50/50 when it comes to holding the right end of the blaster pistol.
Tarkin was all about directness. He wanted to shoot the enemy in the face, rather than shoot them in the leg and wait for them to die.
Actually, this almost makes sense…
Don’t worry. It’ll be fixed in the 3D Blu-Ray release.
For a better fanwank, it’s quite plausible that merely shooting the gas giant wouldn’t do enough immediate damage to keep the rebels from a potential escape. They’ve shown that given enough time, they can put together an evacuation. So destroying the gas giant doesn’t simply need to sometime-eventually destroy Yavin, but do so fast enough that the rebels didn’t engineer another last-minute escape.
It does make sense that they’d want to be absolutely sure this time.