A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Sean C
Date: 2014 Nov 19, 21:41 -0800
I use an Android app, appropriately called "Distance Between Planets" (by: h_maki) and the formula:
sin(HP) = radius of Earth / distance to planet
Once I have the HP, I determine parallax in altitude with the formula:
PA = HP·cos(H)
...where 'H' is the apparent altitude of the body in question.