Editing Observational astronomy (section)

==== Advantages ====
Prior to the invention of photography, all astronomy was done with the naked eye.  However, even before films became sensitive enough, scientific astronomy moved entirely to film, because of the overwhelming advantages:
* The human eye discards what it sees from split-second to split-second, but photographic film gathers more and more light for as long as the shutter is open.
* The resulting image is permanent, so many astronomers can use the same data.
* It is possible to see objects as they change over time ([[SN 1987A]] is a spectacular example).