NEED help tweaking spacing below header image PLEASE

This is driving me absolutely nuts. I am trying to remove the space between the post and the custom header image. Right now I am using the default WordPress theme.

Here is an image for reference and then I will explain in more detail what I am trying to accomplish…

Screenshot.

OK so basically I want the header image to have NO space below it. I will also be removing the title from each post so the post will simply start off with an image, but I want that image to be right up against the bottom of the header image. Does this make sense? I have been messing with CSS margins, padding, etc for literally hours and I can’t pull this off. I got to a point where it was working in Firefox but then in Safari it added an extra little space. Someone please please help!