The wavelengths of red and blue light differ by less than a factor of two. Radio wavelengths can be the size of mountains while gamma ray wavelengths are the size of an atomic nucleus.
Astronomers discover dark stellar companions using the light curve of the star.
As a dark orbiting object eclipses the star, the brightness falls, producing a dip on the light curve. Careful analysis of the light curve reveals the masses of the star and dark companion plus the distance to this eclipsing binary system. A measure of a telescope's ability to collect light . Light gathering power is proportional to the telescope's lens or mirror surface area. Astronomers enjoy observing through large aperture telescopes because they may see faint, distant objects and detail of nearby objects.