Thanks for the information- that's what we were all looking for.
Your beer will NOT be horrible. It will be drinkable and flavorful. It will be a bitter beer, because your first hops addition is the "bittering hops" addition. That's what gives the beer it's bitter flavor up front. Most recipes call for a certain amount of hops at the beginning of the boil- usually 60 minutes. Then, the flavor hops are added with 15 minutes left in the boil, and then finishing hops (if using) are added at 5 minutes or at flameout. So, a recipe that uses these hops might look like this:
6LBS LDME
1 oz perle 60 mins
1/4 oz perle 30 minutes
1/4 oz perle 5 mins
1/4 oz saaz 5 mins.
Your instructions were lacking, to not tell you the amount of hops and when to add them. 1.5 ounces of centennial for bittering is kind of alot. Not bad if you like bitter beers, just more bitter than you might have been expecting.
Also, your hops additions are in the recipe for the amount of time you boil, not the amount of time left. So, the first addition (the 60 mins, for example) is actually boiled for the full 60 minutes, and the others are added to the boil with the correct amount of time left in the boil.
So, you actually added 1.5 ounces at 45 minutes, and .5 ounces at 15 minutes. That way, it makes it easier for us to understand. Your technique was good, and you did a good job with it.
No worries- you've made beer!
Lorena