I do a lot of site scouting during mid-day when the light’s not that great. And during these scouting trips I always have a good compass with me. This way I can determine where the sun will be at sunrise and sunset. And knowing just where the sun or moon will rise or set helps in determining if a location will be worth revisiting at those times.

Sure, you can use some apps in their Virtual Reality mode, but this often requires an internet connection.

You could use the compass on your phone. But is it calibrated? Frankly, I don’t trust electronic compasses to give me accurate results. Real compasses don’t need calibration, just make sure you’re far enough away from your car or other metal objects that could affect the magnetic field.

This is why I recommend getting a decent compass with a sighting mirror and learning how to use it. The compass should also have a declination adjustment. Most compasses you can get at your local REI will have a declination adjustment setting. They also have many models with sighting mirrors. (You can find the magnetic declination, which is the difference between true north and magnetic north from an up to date map, the internet, or by using a smart phone app for magnetic declination)

Sun/moon rise/set info is stored in databases so most apps can give you the needed info without the need to be connected to the internet. Or, and I know this is radical, look up the info ahead of time and write it down (or enter it in a notes app on your phone).

The piece of information you’re looking for is the azimuth. For the sun, look for sunrise and sunset azimuth. And for the moon, look for the same information for moonrise and moonset.

Then combine sun/moon information with a compass to know where the sun/moon will rise/set.

Let’s say you’re trying to see where the sun will rise on the horizon.

Set the compass dial for the sunrise azimuth and point the compass, keeping it level, until the needle lines up with the north indicator. You’re now looking in the direction of the sunrise.

Doing this give you a good idea where the sun will come up. But if you need to know exactly where, that’s where the sighting mirror comes in. Fold the compass cover until you can see the compass ring in the mirror while holding the compass level and at eye height. Move the compass until you can see the needle lined up with the compass ring’s North marking. The sighting line in the mirror should bisect the compass ring. When everything is lined up, look through the mirror case’s sighting groove. That’s where the sun will come up.

Here’s a good video illustrating the process of using the mirror for taking/using a bearing.