Height/Width data

Hello everyone, im excited to become a part of this forum. I currently am stuck on something maybe you can help me with.

ive gotten a bitmap to be centered to stage as you can see:

master_mc.addChild(imageLoader);
imageLoader.x = (stage.stageWidth - Number(rawW)) /2;
imageLoader.y = (stage.stageHeight - Number(rawH)) /2;

i’m trying to center a bitmap within a movie clip now:

so im assuming that “stage.stageWidth” and “stage.stageHeight” would have to be the width and height of the movieclip. I’m not sure how to point directly to my movie clip, whos instance name is “master_mc”

ive tried

master_mc.addChild(imageLoader);
imageLoader.x = (master_mc.Width - Number(rawW)) /2;
imageLoader.y = (master_mc.Height - Number(rawH)) /2;

but that didnt work. any advice?