Optical Design – RASA

• Uses the innovative patented Rowe-Ackermann Schmidt Astrograph (RASA) optical system, which combines a Schmidt corrector, primary mirror, and a four-element glass lens group with rare earth elements.

• This design ensures an extremely flat field, free of aberrations such as coma, field curvature, or chromatic aberrations.

Aperture & Focal Length

• Aperture of 203 mm (8").

• Focal length of 400 mm, corresponding to f/2.0, making it a very “fast” astrograph.

Spectral Range

• Operates effectively over a broad wavelength range, from approximately 390 nm to 800 nm, allowing light collection beyond the visible spectrum and enhancing the overall signal-to-noise ratio of images.

Focusing System

• Features a highly stable focusing system (focuser) with six precision sealed bearings, significantly reducing image shift during focusing.

Air Circulation / Cooling

• Built-in 12 V DC fan system, aiding in rapid thermal equalization of the tube and reducing thermally induced distortions.

Internal Filter Mount

• Equipped with an internal filter holder, enabling the integration of filters (e.g., light pollution filters) without significantly affecting optical quality.

• Additionally, includes a removable optical window, allowing you to remove or replace it with a filter without losing image quality.

Size & Weight

• Tube length approximately 628 mm and diameter approximately 235 mm.

• Weight about 7.7 kg.

• Constructed from aluminum for durability and portability.

Mounting Base

• Features a CGE dovetail (Losmandy / 3″) rail for easy attachment to common equatorial mounts.

Direct Imaging

• Designed exclusively for astrophotography. Does not support visual observation through an eyepiece.

• The short focal length and f/2 ratio enable very short exposure times—many deep-sky objects can be photographed in seconds instead of minutes. Due to this “fast” performance, external guiding (“autoguiding”) is often unnecessary, simplifying setup.

• Ideal for live stacking and “real-time” imaging with modern CMOS cameras.

Light Gathering Capability

• The mirror surface is coated with an enhanced aluminum coating, and the lens elements feature StarBright XLT coatings by Celestron for higher light transmission.

• The optical quality (spot size) is excellent, with < 4.6 µm RMS spot size within the image circle of approximately 22 mm.