1.) It is essential to use many different types of equipment because you want to know what you are seeing and with this equipment you can you also want to make the right obversions like how bright or big a star is.
2.) The missing element would be oxygen. Since earth has carbon and oxygen it makes carbon dioxide so if a different planted has oxygen it will make it so people could breath on it.
Ions are an atom or group of atoms that either has a positive or negative charge. An ion with a negative charge is called an anion and one with a positive charge is a cation.
