Two navigational instruments on my website of the 17th and 18th century where based on the same principal: a staff with vanes. These are the spiegelboog (mirror-staff) and the cross-staff. Often only the staff is found without vanes or with later reproductions of the vanes. This page will help you to:
Identify if the staff you possess is a cross-staff or a spiegelboog
Check if the staff still has its original length (on the eye-end)
Check if the vanes that come with the staff have the proper lengths
In order to do so 2 measurements (L1 and L2) on each side of the staff have to be taken and noted down with the corresponding altitudes A1 and A2 (in this example 80° and 40°) and, if possible, a side number (in this case 2), otherwise leave blank. All measurements on all sides should originate at the same point: the eye end. If the eye-end is shortened, damaged or only a small part of the staff is available a temporary reference can be made by wrapping a piece of paper around the staff and fixating it using a rubber band, then measure from this temporary reference (L1' and L2') on all sides.
If you have any vanes you can fill in their lengths as well together with their numbers. You only need to fill in the fields that you have available.
