... Almost all DSOs require a telescope to see in any detail at all, though some can be detected with just binoculars, and a few can be barely seen with the unaided eye. ... DEGREE: Distances on the sky (sometimes called the celestial sphere) are measured in angular degrees rather than inches or feet. ... The magnification is the focal length of the telescope divided by the focal length of the eyepiece. ... Short focal length eyepieces are also termed high power, long focal length are low power. ...

... A non-linear relationship is observed between the sky brightness on clear and overcast nights, with a change in behavior near the rural to urban landuse transition. ... The great variation in skyglow radiance observed from site-to-site and with changing meteorological conditions underlines the need for a long-term international monitoring program. he introduction of artificial light has caused an unprecedented disruption to the nighttime environment over large areas of the Earth. ... Data processing...