An astrolabe or quadrant is good when measuring a single object. It is possible to measure the difference between things but it requires two readings, one for each object. A cross-staff (also called a Jacob's Staff because it was mentioned in the Bible) is designed to measure two things simultaneously.
It is a bit hard to locate directions and information on a cross-staff so try your hand at the one described at: https://pwg.gsfc.nasa.gov/stargaze/Scrostaf.htm
I built my own Jacob's Staff from a yard stick, 12-inch ruler, paper, tape and rubber bands.
This is how I would use it in the dark.
Try using a cross-staff to measure the angle between:
1. Polaris and the horizon (your latitude)
2. the length of Orion’s belt.My results.
I made sure my alignment marks were equidistant on the cross. I used a tape measure to then measure the distance between the marks on the cross and the distance from the front of the cross ruler to the bottom of the staff where my eye was.
You were standing on the ground when you used all three of the constructed instruments. Navigation at sea was a major concern during the time period these instruments were used. Finding the latitude was a daily chore. Imagine trying to do that on a moving sailing ship.
Using a Jacob's Staff on a ship at night would be difficult. If the sea was calm, you would have to do this at twilight when it is dark enough to see Polaris, yet light enough to see the surface of the sea in the distance. If the ship was in rougher water, this exercise would be very difficult and an approximation at best.
