Angular size can be estimated by stretching out  your hand and using the landmarks indicated.
<a href="//commons.wikimedia.org/wiki/User:Guy_vandegrift" title="User:Guy vandegrift">Guy vandegrift</a> and student who signed image and wrote statement of release under <a href="https://en.wikipedia.org/wiki/Creative_Commons_license" class="extiw" title="w:Creative Commons license">Creative Commons</a> Attribution-Share Alike 4.0
CC BY-SA 4.0
Inspired by two webpages: <a rel="nofollow" class="external free" href="https://dept.astro.lsa.umich.edu/ugactivities/Labs/coords/index.html">https://dept.astro.lsa.umich.edu/ugactivities/Labs/coords/index.html</a> and <a rel="nofollow" class="external free" href="https://www.bartbusschots.ie/s/2013/06/08/photographing-satellites/">https://www.bartbusschots.ie/s/2013/06/08/photographing-satellites/</a>