A bright reference star is easiest to use for parallax work. Select the date and time of the observing session such that all observers can see the object and the reference star. Various sky software can be used to verify that the correct time is selected. Below that value the percent uncertainty due to reaction times becomes significant. The observing time needs to be selected so that it is sufficiently dark for each observer.
Larger baselines yield larger parallax angles, reducing the uncertainty of the computed distance.
Parallax measurements require two observers. If a network of observers is established, then the possibility of all observations being blocked by clouds is greatly diminished. All rights reserved.