How do we know that our sperm is healthy using old manual microscope. ruling out azoospermia or oligospermia?

Count and movement: Microscopic examination will let you know if there are any sperm present (ruling out azoospermia), and if there are enough of them (ruling out oligospermia). It will also tell you if they are swimming vigorously or slowly, and if their shapes are normal or malformed. All of this gives you an idea of how healthy the sperm are.

Azoospermia easy: There will be no sperm seen in the ejaculate. Oligospermia probably needs to checked by a lab. Unless you have special equipment used to quantitate and know how to use it. This can be done on an old manual microscope, if you know what you are doing.