You can also lodge a telephone complaint while you are in Australia by ringing the Australian Consumer Affairs and Fair Trading Hotline 1300 552 263 (local call cost within Australia). The call will be automatically forwarded to the fair trading agency in the state or territory from which you are calling.
Circular paraboloid. A parabolic (or paraboloid or paraboloidal) reflector (or dish or mirror) is a reflective surface used to collect or project energy such as light, sound, or radio waves. Its shape is part of a circular paraboloid, that is, the surface generated by a parabola revolving around its axis. The parabolic reflector transforms an incoming plane wave traveling along the axis into a spherical wave converging toward the focus.
Almost all of the major telescopes used in astronomy research are reflectors. Reflecting telescopes come in many design variations and may employ extra optical elements to improve image quality or place the image in a mechanically advantageous position. mid-20th century innovation was catadioptric telescopes such as the Schmidt camera, which use both a spherical mirror and a lens (called a corrector plate) as primary optical elements, mainly used for wide-field imaging without spherical aberration.