Newtonian telescope secondary mirror. This design reduces the size and cost of the telescope with a shorter overall telescope tube length (with the corrector extending the focal length in a "telephoto" type layout) combined with a less costly spherical mirror. Commercially produced versions of this design have been noted to be optically compromised due to the difficulty of producing a correctly shaped sub-aperture corrector in a telescope targeted at the inexpensive end of the telescope market. Newtonian telescope The Newtonian telescope, also called the Newtonian reflector or just the Newtonian, is a type of reflecting telescope invented by the English scientist Sir
Galilean electromagnetism such as when Faraday's law of induction was insignificant. The magnetic limit applies when the magnetic field effects are dominant. Jackson introduces a Galilean transformation for the Faraday's equation and gives an example of a quasi-electrostatic case that also fulfills a Galilean transformation. Jackson states that the wave equation is not invariant under Galilean transformations. In 2013, Rousseaux published a review and summary of Galilean electromagnetism. Galilean electromagnetism Galilean electromagnetism is a formal electromagnetic field theory that is consistent with Galilean invariance. Galilean electromagnetism is useful for describing the electric and magnetic fields in the vicinity of charged bodies moving