To determine where your background will show up, do the following.
Take the pitch of your background, and 'imagine' applying the same pitch to a ship at coordinates {0,0,0}. Then, take the heading of the background, and 'imagine' applying the same heading to the same ship at coordinates {0,0,0}. The ship should now be pointing at your background.
Note that the heading and pitch values for ships are done in radians, while those of backgrounds is done in degrees. You'll have to do some conversions to figure out how much to change the ship's pitch and heading values.
To make it more confusing, the heading value for backgrounds increases as one goes counterclockwise. However, this is not true for the heading value for ships, which increase as one goes clockwise. The same disparity is true for pitch values, so be careful!