Focal Reducers for Schmidt-Cassegrains
The common f/6.3 focal reducer for Schmidt-Cassegrain telescopes was originally designed to compress the existing f/10 light cone down into an area that would cover a 35mm film frame. These focal reducers are still commonly used today with CCD cameras for Schmidt-Cassegrain astrophotography. It's worthwile to note that standard focal reducers cannot be used with telescopes designed to produce a flat field because they will actually introduce an optical aberration. Specially designed focal reducers are needed for use with the Celestron EdgeHD optical system. SCT focal reducers are equipped with a female SCT thread on the input side, and a male SCT thread on the output side.
Focal Reducers for Refractors
Focal reducers for refractors must be matched to the focal length of the instrument due to the relationship between focal length and field curvature. Some refractors, notably the TeleVue "NP" or Nagler-Petzval and Takahashi "FSQ" have inherently flat fields and should not be used with standard focal reducers.
Telescope Focal Reducers
Telescope focal reducers provide a brighter, wider image and a reduced exposure time. Telescope focal reducers also work as field flatteners, reducing field curvature to provide the flat field necessary for astrophotography.
A focal reducer works using a positive lens, which shortens the focal length by causing the incoming beam of light to converge more quickly. The shorter the focal length, the greater the focal reducer’s reduction factor when placed into a telescope’s optical path. This also decreases the effective focal ratio of the instrument.
The focal reducer’s power is also affected by the distance between the reducer lens and the focal plane — shorter distance results in a longer focal length, while longer distance results in a shorter focal length. For example, a standard Celestron 6.3 focal reducer with 0.63x power reduces a f/10 telescope to f/6.3 if it is placed 100mm from the focal plane. If the distance is decreased, the focal ratio increases. If the distance is increased, the focal ratio decreases.
Skies Unlimited is proud to offer the highest quality telescope and refractor focal reducers for top brands including Celestron, Meade and more.
Reducers from Skies Unlimited
Skies Unlimited offers quality focal reducers sale for a variety of products, including Celestron focal reducers and refractors. On top of our selection, we offer the knowledge you need to choose the best reducers to fit your needs. Established in 2004 by amateur astronomers, we strive to make astronomy as accessible as possible. We only hire amateur astronomers so you can rely on us for abundant, practical and professional knowledge. No matter what you need help with, from basic specification information to detailed recommendations, Skies Unlimited is here to help.
Are you wondering what type of reducer is best for your TeleVue Nagler-Petzval refractor? Skies Unlimited can help with any question you have. Call us today or visit our physical location just outside of Pottstown, Pa., to speak with one of our representatives.