A much more comfortable observing position can be achieved with a refractor or catadioptric telescope by using an erecting lens. The beam of light exiting the telescope is deflected by 90° before it enters the eyepiece. In this way, even objects close to the zenith can be observed comfortably.
Celestron
zenith prism 90°, 1.25"
( 5 / 5 )
$ 53.00
ready for shipping in 24
h
Omegon
Pro Penta Prisma 90° 1.25''
$ 239.00
ready for shipping in 24
h
Baader
Diagonal prism 2" ClickLock BBHS®
$ 590.00
ready for shipping in 1-2
weeks
Baader
Zenith prism T-2/90 degree, 32mm
$ 159.00
ready for shipping in 1-2
weeks
Omegon
Pro 1.25'', 45° penta-prism
$ 189.00
ready for shipping in 24
h
Baader
90°, T2 star diagonal with 35mm of free aperture
$ 284.00
ready for shipping in 1-2
weeks
APM
Diagonal prism with quick-release fastener 2"
$ 256.00
ready for shipping in 1-2
weeks
TS Optics
Diagonal prism T2 90°
$ 104.00
ready for shipping in 3-7
days
Baader
Zenith prism T-2/90° 32mm prism
$ 129.00
ready for shipping in 1-2
weeks
William Optics
Diagonal prism RedCat 90° 1,25"
$ 186.00
ready for shipping in 3-5
weeks
APM
Roof prism with quick-action lock 2"
$ 345.00
ready for shipping in 1-2
weeks
Erecting lenses are available as zenith mirrors, zenith prisms or Amici prisms. The latter are useful for terrestrial observation and are therefore also available with a flatter deflection angle of 45°.
- Without an erecting lens, the image in the telescope depicts north below and east to the right.
- With zenith mirrors and zenith prisms, the telescope depicts a laterally transposed image: north is at the top, east is at the right and, without tracking, stars wander to the left.
- Amici prisms show a correct image as it would be seen with the naked eye. Therefore, these prisms are essential for nature-watching. However, their more complicated construction makes them susceptible to image defects, which is why the laterally transposed image is preferred in astronomy.
Most erecting lenses have simple plug-in connectors, as is common seen with eyepieces. For SC telescopes, however, there are also models with screw threads.