The way I look at it, the Death Star's superlaser only works on rocky worlds, not gas giants.  The laser dissipates when traveling through the dense atmosphere.

Hence, they can't blow up or shoot through Yavin - they have to go around it.

I'm fond of this explanation:

Sluggo said:

Or maybe this?

and this, but not so much at the beginning:

If Yavin/Moon relationship is anything like Jupiter/Earth size relationship, then the planet Yavin is about 1,300 times bigger.

I'm perfectly willing to beleive that "the power to blow up a planet" means the power to blow up a rocky planet, roughly similar to Alderaan, not the power to blow up ANY planet.

I'll also buy that the DS needs to recharge. I'll buy that it's too close to the gas giant.  It all makes sense. What I won't buy is that all the characters are just too stupid to do it.

I feel that 2/3 of complaints about the SW movies are that a fan invents a rule that's not in the movie, then complains that the movie doesn't follow it.

I always went by the thought that it needed a lot of time to charge up its capacitors enough to blow away a whole planet.  Also, even if they had destroyed Yavin first, it may have still been out of effective range of destroying the moon from over there.

The novel of Star Wars mentions that the Death Star gets to about six planetary diameters distance of Alderaan at the point they fire the superlaser.  Going by the size of Earth, this would be about 50,000 miles, which is rather less than the distance from here to our moon.  In the potentially much larger orbital system of a gas giant, it seems unlikely they'd be able to fire from the far side of Yavin and get the job done.  Now it's probably safe to assume that this number was arbitrarily invented by Alan Dean Foster when he wrote the book, but the concept of effective range is valid regardless of the exact value.

For the second Death Star, not only could they recharge faster, but also it would require far less power to destroy a ship than an entire planet, enabling a much higher rate of fire at the Battle of Endor.

ooohhh yeah...but leia new the falcon was getting tracked down by the empire why did she still go to the HIDDEN rebel base???

X-wing fighter said:

ooohhh yeah...but leia new the falcon was getting tracked down by the empire why did she still go to the HIDDEN rebel base???

 Because it was time to fight. The Death Star was the Ultimate Power in the Universe, and the Rebs had one shot to take it out.

thanks for the replies and answers guys