Revise guidelines

Author: cjsha

source/Hardware Guide/Lighthouses/setup.rst

@@ -12,11 +12,15 @@ Setup
 
    Follow these guidelines to decide where to mount your two Lighthouse base stations:
 
-   - They should be centered above and facing the area that will be occupied by the lighthouse receivers.   
-   - The distance between the receiver and the transmitters should not exceed 3 meters. Each base station 
-     has a 120° field of view. However, position measurements are noisier when receivers are at the boundary 
-     of the transmitters' range, so leave a safe margin. A receiver must be in range of both transmitters 
-     in order to measure position. 
+   - They should be centered above and facing the area that will be occupied by the lighthouse receivers.
+   - The lighthouses should have the same orientation.
+   - The distance between the receiver and the transmitters should not exceed the maximum range. This depends 
+     on the sensitivity of the receiver's photodiode on the headstage and is best determined experimentally. Each 
+     base station has a 120° field of view. However, the photodiode has a larger chance of being obstructed from 
+     the transmitter by parts on the headstage at larger angles.
+   - Position measurements are noisier when receivers are at the boundary of the transmitters' range, so leave a 
+     safe margin. 
+   - A receiver must be in range of _both_ transmitters in order to measure position. 
    - Secure the base stations such that they can't be easily jostled or moved.
 
    .. tip::
@@ -29,7 +33,6 @@ Setup
       using Bonsai to acquire Onix data to do this, visit the OpenEphys.Onix1 Bonsai package 
       `Getting Started page <https://open-ephys.github.io/bonsai-onix1-docs/articles/getting-started/index.html>`_.
 
-
    The image below shows a cartoon of what a lighthouse setup might look with a commutator as well mounted
    on extruded aluminum rail. The overlapping green area represents the region where a TS4231 device is in 
    range of both base stations and can measure position.