RASA 6" - Rowe-Ackermann Schmidt Astrograph
Celestron's transportable astrograph, the 6" Rowe-Ackermann Schmidt Astrograph (RASA), can capture spectacular deep-sky wide-field images in seconds. This incredibly fast f/2.2 system is the perfect telescope for modern astronomical CMOS color cameras, smaller CCD cameras.
Thanks to the large focal ratio and the patented optical design, you can produce sharp, detailed images and in many cases completely dispense with an autoguider. With a weight of only 3.8 kg (8.4 pounds), it is easy to transport the 6" RASA to even the most remote locations.
RASA performance for everyone
The 6" RASA is a telescope designed purely for photography, providing a flat field of view with no optical aberrations to show extremely sharp stars over a wide field of view. It provides astronomical images with impressive "depth" and avoids the problems typically associated with longer focal length (and slower focal ratio) instruments.
The latest addition to the RASA family is a much more portable and affordable 6" aperture version of the RASA 11, which was launched in 2014 to great acclaim. With the 6" RASA, the benefits of the RASA design are now available to a wider range of astrophotographers. It shares many features with its "big brother" RASA 8, including the integrated cooling system, the StarBright XLT coating and the robust CGE dovetail mount.
The 6" RASA is designed exclusively for photography and cannot be used visually. The focal plane is located at the front of the optical system, so the telescope cannot accept a conventional eyepiece.
Shorterexposure times and virtual "real-time" observation
Because it is an f/2.2 optical system, astrophotographers can use shorter exposure times to capture details in faint objects. In combination with sensitive cameras and the right "live stacking" software, the 6" RASA also makes near-live observations possible: you can instantly view and stack the images on a computer, making them brighter and more detailed than with the naked eye - even compared to much larger telescopes!
As shorter exposure times are possible, your mount does not have to track with high precision over long periods of time. The short focal length of 335 mm of the 6" RASA further reduces the tracking requirements. In many cases, autoguiding is not necessary. With a weight of only 3.8 kg, this telescope fits perfectly with a large number of commercially available mounts.
Ultra-stable focusing system
The RASA 6 also features the improved focusing mechanism, which reduces the play of the primary mirror when focusing, slewing or tracking the astrograph. Focusing is easier, more precise and more stable than ever. The key to this ultra-stable focusing system is two sets of precision bearings that are precisely aligned and tested during assembly for optimal results.
Unique optical design
The patented RASA design (US 2016/0299331 A1) consists of a Schmidt plate, primary mirror, lens group and optical window. The lens group consists of three elements and uses rare earths. The device is optimized for the spectral range of 400-700nm. This allows more light from celestial objects to be collected and imaged sharply.
A 2" clear glass filter is integrated into the RASA 6. It can be replaced by a nebula filter of the same thickness, for example, without additional glass entering the focus path. This means that the focus position and optical performance do not change even when a filter is used.
With many optical systems, it does not matter for the imaging quality whether an additional flat glass is used like a filter. The situation is different with extremely fast systems such as the RASA. Our developers have solved this problem by providing the RASA with an optical window that can be removed and replaced with a filter. This means that the image quality remains at the highest level even if you use a filter or the camera has its own optical window. Celestron offers a filter against light pollution which was specially developed for the 6" RASA and which replaces the optical window.
All refractive optical surfaces are StarBright-XLT coated, the primary mirror has an improved aluminum coating. This ensures high transmission for the entire system. Compared to the HyperStar system for Schmidt-Cassegrains, the RASA 6 delivers better optical performance and superior illumination.
Advanced features and versatility
Designed with the modern astrophotographer in mind, the RASA 6 is packed with features that enhance ease of use and adaptability:
- Built-in filter system
The built-in filter drawer accepts both 1.25", and 2" filters, giving you the flexibility to use a variety of broadband and narrowband filters. The removable 2" clear glass filter (i.e. the optical window) allows you to add optional filters if desired without adding additional glass to the optical path, which could compromise performance at f/2.2.
- Integrated cooling system
A 12V MagLev fan draws air through mesh vents to quickly cool the system down to ambient temperature to deliver the best images while keeping the internal components dust-free.
- M42 camera adapter
The included camera adapter for the RASA 6 has a standard M42 thread that makes it easy to mount a variety of astronomical CMOS cameras.
Designed for the most modern cameras
In contrast to the larger RASAs, which are optimized for DSLR and large CCD cameras, the 6" model was developed for astronomical CMOS cameras and smaller CCD cameras. The telescope does not work with standard DSLR cameras due to the available back focus. It is optimized for sensors with a diagonal of up to 16 mm and still offers good performance on sensors with a diagonal of up to 22 mm (sensors with a diagonal of 22 mm also work well, but reduced field illumination in the corners must be expected). Furthermore, we do not recommend combining the RASA 6 with a camera body with a diameter of more than 75 mm.
To achieve the highest level of performance, we strongly recommend combining this telescope with the focus motor, the 6" aluminum dew cap, the 6" heating ring and the 6" RASA bag (all sold separately). The focus motor allows you to set a sharp, precise focus electronically using the same computer you use to control your camera. The dew cap or dew heater will help you keep the optics clear during long periods of observation, especially in humid conditions. When you are not using your telescope, you can store and transport your RASA in the protected, portable bag. The 6" RASA offers the perfect blend of speed, precision and portability. Its revolutionary optical design and robust mechanical features allow you to image the night sky like never before. A take-anywhere astrograph that opens up a vast, limitless universe.
