- Air Mass (Astronomy) - Wikipedia - a Wikipedia page pointing out a few formulations for the airmass function
- Frederick R. Chromey. 2010. To Measure the Sky: An Introduction to Observational Astronomy. ISBN: 9780521763868 - the link points to a few pages on how to determine the extinction coefficient
- Determining the atmospheric extinction coefficient using visual brightness estimates - 'in development' methodology to determine the extinction coefficient. The accuracy is not that great (first non-zero digit), but it's enough for visual estimates.