When teaching Celestial Communication, Yogi Bhajan said that it is great to practice it with others, a leader and follower(s), to achieve the mirror effect. This could also be done by watching a video or by practicing Celestial Communication in a mirror and seeing your own reflection. But, Yogi Bhajan said, when you don't have any of these things, sit or stand in front of a tree and do Celestial Communication.
In the photos below (taken by my lovely husband, Sat Sang), I am Celestialing with a tree at the Huntington Gardens. Try it sometime - it is great fun!
Many blessings, Adarsh Kaur