Finding the Air Mass and Zenith Distance

This appendix gives some advice on how you can find out the air mass and zenith distance of your individual observations. It is impossible to give simple instructions which will work in all cases because the procedures adopted by different observatories are different. Ideally, at the conclusion of your observing run you would be given a summary list of all your observations which would include the air mass for each. However, it is much more likely that the air mass or zenith distance will be included in the auxiliary information stored in the data file for each observation. Again, different observatories use different data formats and different keywords¹⁷.