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This multireflected light path results in the compact design of the ETX, yielding a much longer focal length (optical length) than is otherwise possible. This last reflection sends the light back towards the rear of the ETX OTA where, using a “flip mirror”, it is directed to the normal eyepiece position or out the rear port on the back of the ETX tube. I put in the batteries as directed, connected the Autostar unit an tutn on the power switch.no power. It then proceeds down the tube to a mirrored surface (the primary mirror), where it is reflected back up the OTA only to be reflected again from a small “spot” (secondary) mirror on the inside of the corrector lens. Light enters the telescope through a coated corrector lens at one end of the ETX optical tube assembly (OTA). The Maksutov-Cassegrain design uses a lens and mirrors to focus the light, as shown in Figure 1.1. The original ETX brought this efficient design to many more amateur astronomers at an affordable price. The Maksutov-Cassegrain design of the original ETX was used previously in the highly sought after but pricey Questar 3.5-inch telescope. Other telescopes were available that used alternative designs, but they were typically expensive and not appropriate for the mass-market amateur astronomer. Prior to the ETX, most inexpensive consumer telescopes came in two varieties: the refractor telescope, which uses a glass lens at the top to focus the light, and the Newtonian reflector telescope, which uses a curved mirror (actually a spherical surface) at the bottom to reflect and focus the light.
#Meade autostar etx 70 vs etx 60at series#
Patrick Moore’s Practical Astronomy Series