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RASA stands for Rowe Ackermann Schmidt Astrograph: Dave Rowe and Mark Ackermann are renowned optical instruments developers.
These telescopes have been specially developed for astrophotography. RASA astrographs have a very fast aperture ratio of f/2. You capture images twenty times faster than with an SC optic with f/10! This eliminates the need for tracking control (guiding). Even with an altazimuth mount, deep sky images are possible!
The optics have a four-lens corrector with rare earth glass that suppresses colour and image defects.
Engineered for Excellence: The Celestron RASA 8!
If you’re in the market to elevate your astrophotography game, the Rowe-Ackermann Schmidt Astrograph from Celestron is the solution. Offering an unbeatable native focal ratio of f/2, this Celestron 8” RASA is an astrophotographer’s dream! Couple this unrivaled light gathering power with the superior optical technology from Celestron and enjoy bright, astigmatism-free images. Perfect for deep space enthusiasts, the focal length of 400 mm is great for capturing large portions of the night sky in a single frame. Whether you plan to reveal intricate dust lanes within galaxies or exquisite structure in nebulae, this RASA 8 from Celestron is sure to take your images to the next level.
Designed for those serious about astroimaging, Celestron has carefully crafted this OTA to feature everything an astrophotographer wishes for. Not only is the light gathering power and speed impressive, but the optical elements within this RASA 8 provide an inherent flat field, razor sharp stars, and photos absent of aberration. In addition to this, rest assured knowing every bit of detail is being collected as the patented CelestronStarBright XLT coatings ensure maximum light transmission to your camera sensor. Celestron has also furnished their RASA series with mechanisms such as a smooth internal focuser and an integrated telescope cooling system to enhance your astrophotography experience even further. With qualities like these, Celestron delivers an astrograph that’s a cut above the rest!
The Unmatched Optical Design of the Celestron RASA
Taking the already incredible astrophotography performance of the Schmidt-Cassegrain optical design up a notch, Celestron has developed the Rowe-Ackermann Schmidt Astrograph for those serious in their imaging endeavors. RASA telescopes consist of a lens group, a Schmidt corrector plate, a primary mirror, and an optical window. After passing through the Schmidt corrector plate, the incoming light hits the primary mirror, then is redirected to the lens group. This lens group is composed of four elements of rare-earth material, correcting for field curvature, false color and aberration, and provides a significant reduction in vignetting. When it comes to speed, the RASA does not disappoint. These patented Rowe-Ackermann Schmidt Astrographs feature a native focal ratio of f/2—an outstanding improvement from standard f/10 Schmidt-Cassegrain telescopes! With a focal ratio this low, more light is able to be collected on your camera sensor in less time. This results in brighter, more detailed images and projects to be completed far quicker.
For instance, a 30 second exposure with the RASA is equivalent in brightness to a ~10 minute exposure with an f/10 SCT. That’s 20x as fast! In addition to faster collection of signal, RASA optical assemblies also offer an increased range of signal collection. A large majority of telescopes deliver peak performance in the visible spectrum (400 nm to 700 nm), while the RASA excels within a wider spectral range of 390 nm to 800 nm. This increase allows for a greater collection of light on celestial bodies. To enhance performance even further, Celestron has included enhanced aluminum coatings on the primary mirror, as well as their patented StarBright XLT coatings on the refractor elements for maximum light transmission to your camera sensor.
Unique Optical Design
RASA’s optical design is patented (US 2016/0299331 A1). The design consists of a Schmidt corrector, primary mirror, lens group, and optical window. The lens group contains 4 elements and utilizes rare-earth elements. Unlike many telescopes that only perform well over the visible spectrum (400-700nm), the 8” RASA’s optics are designed to perform over a wider spectral range, from 400nm – 800nm. This allows more of the light emitted from the astronomical object to be sharply focused in the image.
With many imaging systems, adding an extra piece of flat glass such as a filter does not change optical performance. However, that is not the case with super-fast optical systems like the RASA. Our engineers addressed this by designing the RASA with a removeable optical window, so you can maintain peak optical performance if a filter is added or if a camera has its own optical window. Celestron offers a Light Pollution Imaging Filter designed specifically for the 8” RASA, which mounts in place of the optical window.
All refractive optical surfaces are coated with StarBright XLT coatings, while the primary mirror uses enhanced aluminum coatings. This maintains high light transmission through the entire optical system.
When compared with “Hyperstar SCT” systems, the RASA 8 provides better optical performance and field illumination.
