Celestron RASA – 8″

Celestron’s portable 8″ Rowe-Ackermann Schmidt Astrograph (RASA) can capture spectacular wide-angle deep-sky images in seconds. This incredibly fast f/2.0 system is the perfect telescope for modern astronomical CMOS color cameras, smaller CCD cameras, and mirrorless cameras.

Thanks to its large aperture ratio and patented optical design, you can produce sharp, detailed images and, in many cases, completely forgo an autoguider. Weighing only 7.7 kg, the 8″ RASA is easy to transport, even to the most remote locations.

RASA performance for everyone:
The 8″ RASA is a telescope designed purely for astrophotography, delivering a flat image field free of optical aberrations and thus showing extremely sharp stars across a wide field of view. It enables astronomical images with impressive depth and avoids the problems typically encountered with instruments with longer focal lengths (and slower aperture ratios). The 8″ RASA shares many features with its „big brother,“ the RASA 11, including the integrated cooling system, internal filter holder, and robust CGE dovetail mount.

Note: The 8″ 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 accommodate a conventional eyepiece.

Shorter exposure times and virtual „real-time“ observation:
Because it’s an optical f/2.0 system, astrophotographers can use shorter exposure times to capture details in faint objects. Combined with sensitive cameras and the right live-stacking software, the 8″ RASA also allows for near-live observations: 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!

Since shorter exposure times are possible, your mount doesn’t need to track with high precision for extended periods. The relatively short focal length of 400mm of the 8″ RASA further reduces tracking requirements. In many cases, autoguiding is unnecessary.

Ultra-stable focusing system:
With the introduction of the 8″ RASA, Celestron presents a focusing mechanism that reduces primary mirror play when focusing, slewing, or tracking the astrograph. Focusing is easier, more accurate, and more stable than ever before. The key to this ultra-stable focusing system lies in two sets of precision bearings, which are precisely aligned and tested during assembly to achieve optimal results.

Unique optical design:
The patented RASA design consists of a Schmidt corrector plate, primary mirror, lens group, and optical window. The lens group comprises four elements and uses rare-earth elements. Unlike many other telescopes that perform well only in visible light (400-700nm), the 8″ RASA is designed for a wider spectral range , from 390-800nm . This allows more light from celestial objects to be collected and sharply imaged.

With many optical systems, the use of an additional flat glass element, such as a filter, has no impact on image quality. However, this is different with extremely fast systems like the RASA. Celestron engineers have solved this problem by incorporating an optical window into the RASA that can be removed and replaced with a filter. This ensures that image quality remains at its highest level even when using a filter or when the camera has its own optical window. Celestron offers a light pollution filter specifically designed for the 8″ RASA that replaces the optical window.

All light-refracting optical surfaces are StarBright-XLT coated , and 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 8 delivers better optical performance and superior illumination.

Rasa 8″ Sensor Size

Designed for the most modern cameras:
Unlike the larger RASA models, which are optimized for DSLRs and large CCD cameras, the 8″ model was designed for astronomical CMOS color cameras , smaller CCD cameras , and mirrorless cameras. 

NOTE: Due to its limited back focus, the telescope is not compatible with standard DSLR cameras. It is optimized for sensors up to 22mm diagonally and still performs well with sensors up to 32mm diagonally. APS-C format sensors, commonly used in many mirrorless cameras, are a good choice. While 42mm full-frame sensors will technically work, edge-to-edge performance will be poor, and field illumination will be reduced. Furthermore, we do not recommend using the RASA 8 with a camera body larger than 10cm in diameter.

The following table will help you determine if your camera is compatible with RASA 8.

Spec:

• Optical design: RASA
• Aperture: 203mm (8″)
• F Ratio: 2.0
• Back focus: 29mm from the front lens group / threaded mount, 25mm from the
• included camera adapters
• Image field: 22mm (0.86″) Ø, 4.6° minimal power loss at the corner of the image field
• Focal length: 400mm
• Central Obstruction: 93mm (46% of the opening)
• Light gathering power (compared to the human eye): 843x
• Coating: StarBright XLT
• Usable field: 32mm (1.26″) Ø, 4.6° minimal power loss at the edge of the FOV
• Material: Aluminum
• Tube weight: 7.7kg
• Tube length: 628mm
• Dovetail compatible: CGE (3″ Losmandy-Style)

Whats included:

1. 8″ RASA
   
2. M42 Camera adapter
   
3. Battery holder for fan
   
4. 3″ Losmandy standard dovetail bar