More about the series OTA...
The Schmidt-Cassegrain optics by Celestron:
Despite the long focal length of these telescopes, the OTA itself has a very short length, making the system a compact telescope which is extremely easy to transport. Light first hits an aspherically figured Schmidt corrector plate and is then thrown onto a spherical main mirror. This reflects the light back up, throwing it onto a secondary mirror which subsequently throws it back in the direction of main mirror. The light then passes through a central hole in the main mirror and into the focuser at the bottom of the OTA. Thus the system is closed and hence does not suffer from air turbulence which could degrade the image. Of course this also means that the system is optimally protected from dust. The Schmidt plate is multi-coated, ensuring bright images which do not suffer from stray light reflections.
This telescope provides a very good image, boasting high contrast and definition and provides a lot of pleasure when planetary observing. The Schmidt-Cassegrain design provides a good all-round system suitable for both observing and astrophotography and with an enormous range of optional accessories available. Using the bottom end of the OTA to look through means easy orientation. The system is also optimal for occasional terrestrial observing, e.g. birdwatching at close range. Celestron SC telescopes have an aperture ratio of around 1:10 which, so astrophotography is also very easily possible.
Main mirror focusing means a very large range of focus is made available, which allows virtually any common accessory to be used. Two pre-loaded ball bearings are used in the main mirror focus positioning mechanism in order to prevent 'mirror shift' - a typical problem when using simple bushings. The use of high quality materials such as CNC-milled aluminium components, cast steel and stainless steel guarantees extreme robustness with low weight. This means that a very heavy mount is unnecessary, not always the case for other telescope designs.
Features of the optics:
- long focal length with short OTA
- low weight aluminium OTA
- high quality XLT multi-coating
- closed system
- pre-loaded ball bearings for low mirror shift main mirror focusing
Included in delivery with the telescope:
- OTA with 235mm aperture and 2350mm focal length
- 25mm Ploessl eyepiece
- 1.25" star diagonal
- mounting rail
- 6x30 finder scope, straight-view
It not only matters which telescope you buy but also where you buy it. Our additional services:
- We are a leading telescope dealer and know the devices we sell. Our customer service team will gladly help you after your purchase if you have problems with assembly or operation.
- We provide a copy of the 80-page Telescope ABC beginners handbook with every telescope.
Our expert comment:
Celestron supplies OTAs either with the wider 3" mounting rail (Losmandy style) or the narrower AS-GT rail (Vixen-style). The rail used with the respective product can be identified by the product picture or in 'Specifications' in the 'Included Accessories' section.
Stefan Taube
