TS Optics 62/520 f/8.4 Quadruplet Flatfield Refractor OTA
The TS Optics 62/520 Quadruplet Flatfield Refractor is one of the most versatile compact optical instruments available for mobile use. In a single lightweight package weighing approximately 1 kg and measuring just 310 mm in transport length, it functions as a visual telescope, a daytime spotting scope, a long telephoto lens for landscape and wildlife photography, and a capable wide-field astrophotography instrument. The four-element optical system handles all of these roles with a level of optical quality that goes well beyond what simpler refractors of similar size can offer.
Four-Element Optical Design
Unlike standard doublet or triplet refractors, the TS625Q uses a four-element optical system arranged in two groups. This design achieves two goals simultaneously: improved chromatic aberration correction compared to simpler lens configurations, and an internally integrated field flattener that keeps stars sharp and round across the entire image circle - all the way to the corners of the frame. There is no need to purchase a separate field corrector for APS-C astrophotography, as the correction and illumination are already optimized for sensors of that size and smaller. All optical surfaces carry full multi-coatings, ensuring high contrast and minimal light loss.
Focuser and Connections
The 1.25″ Crayford focuser runs on ball bearings for smooth, backlash-free movement, and features a locking screw that holds the focus position securely - particularly useful during astrophotography sessions where vibration or the weight of a camera could otherwise cause focus shift. The exceptionally generous back focus range of 70 to 125 mm from the 1.25″ receptacle and a total focuser travel of 55 mm ensure compatibility with the full range of common visual and photographic accessories without any need for extension tubes.
On the camera side, a T2 photo thread is already integrated, so connecting a camera requires only the appropriate T-ring for your camera mount (Canon EOS, Nikon F, Sony E, etc.) together with a 20 mm T2 extension tube to reach focus comfortably. When the 1.25″ eyepiece adapter is removed, an SC male thread is exposed, providing an additional connection option for compatible accessories. A universal mounting plate with two 1/4″ tripod threads is included, making it straightforward to attach the refractor to any standard photo tripod.
Visual and Daytime Observation
As a visual instrument, the TS625Q delivers a bright, high-contrast image thanks to its fully multi-coated optics. For astronomical use, standard 1.25″ star diagonals provide a comfortable viewing angle and an erect, mirror-reversed image suited to sky observation. For daytime use - birdwatching, wildlife, landscapes, or events - a 45° or 90° Amici prism produces an image that is both erect and laterally correct, making the telescope function as a high-quality spotting scope with a long 520 mm focal length.
In astronomical terms, the telescope performs well on the Moon, double stars, and bright deep-sky objects. A magnification range from around 20x with a wide-field eyepiece up to approximately 100x for detailed work covers the most useful range for an instrument of this aperture.
Astrophotography and Autoguiding
For astrophotography, the integrated two-element corrector group ensures that stars are rendered as tight, round points across the entire APS-C image circle. With a 520 mm focal length at f/8.4, the field of view is well matched to extended deep-sky objects such as nebulae and galaxies, while the relatively slow focal ratio is forgiving in terms of tracking accuracy requirements. Users with full-frame cameras should expect some vignetting toward the corners of the frame.
The TS625Q also makes an excellent guide telescope for main imaging instruments up to 10″ aperture. The long back focus and 1.25″ focuser are compatible with all common autoguider cameras and guide camera ports. Using a 1.25″ diagonal mirror is recommended for comfortable and precise focusing of the guide camera.
Technical Specifications
- Aperture: 62 mm
- Focal length: 520 mm
- Focal ratio: f/8.4
- Optical system: 4 elements in 2 groups (quadruplet flatfield)
- Theoretical resolution: 1.9″
- Coatings: full multi-coating on all air-to-glass surfaces
- Focuser: 1.25″ Crayford with ball bearings and locking screw
- Focuser travel: 55 mm
- Back focus: 70-125 mm from the 1.25″ receptacle
- Connections: 1.25″ with compression ring, T2 photo thread, SC male thread (with adapter removed)
- Included accessories: universal mounting plate with 1/4″ tripod threads
- Transport length: 310 mm
- Dew shield diameter: 84.5 mm
- Weight: approx. 1 kg
