There are many amateur astronomical techniques and activities associated with deep-sky objects. Some of these objects are bright enough to find and see in binoculars and small telescopes. But the faintest objects need the light-gathering power of telescopes with large objectives, and since they are invisible to the naked eye, can be hard to find. This has led to increased popularity in GoTo telescopes that can find DSOs automatically, and large reflecting telescopes, such as Dobsonian style telescopes, with wide fields of view well suited for such observing. Observing faint objects needs dark skies, so these relatively portable types of telescopes also lend themselves to the majority of amateurs who need to travel outside light polluted urban locations. To cut down light pollution and enhance contrast, observers employ “nebular filters” designed to admit certain wavelength and block others.