If you want to zoom in for detail and still see further ahead, most radars have the ability to offset your own ship's position from the center of the screen.
If your ship's position is offset, the bearing scale is no longer useful. For example, the orange Electronic Bearing Line (EBL) is 90 degrees from your bow, but points to 120°.
As you zoom in or out, the pulse length will usually change automatically. Many radars let you manually change the pulse length.
Short pulses are used when you zoom in and want good separation between targets or more detail. Long pulses are used for long distances, but objects close together may blend into one target.