The Wynne-Riccardi Astrograph

Wynne-Riccardi 305mm AstrographWynne-Riccardi 305mm Astrograph
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APM Telescopes presents a premium type of Astrograph with an extremely fast focal ratio and high performance CCD imaging capabilities. The Wynne-Riccardi Astrograph – named after its optical designer Massimo Riccardi and the built-in 3-element ED Wynne corrector – is available in four different models, starting with a primary mirror of 305mm in diameter. Both in combination allow the short focal length of only f/2.8 (305mm and 406mm) / f/2.5 (560mm and 600mm) without limiting the optical quality.

The conical primary mirror has a center hole for easy mounting and back meniscus shape for fast cool down. It also implements the system's unique feature: Primary mirror focusing with center axis zero image shift. The front corrector with backfocus stays fixed. This keeps the central obstruction as small possible, enables precise adjustments and therefore superior astrophotography results can be achieved. The primary mirror motor focuser with spindle linear-actuator-motor (stepper motor with 1/100mm resolution) has a USB connector port for controlling the focuser remotely from a PC.

Wynne-Riccardi 305mm AstrographWynne-Riccardi 305mm Astrograph
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Wynne-Riccardi 305mm AstrographWynne-Riccardi 305mm Astrograph
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Wynne-Riccardi 305mm AstrographWynne-Riccardi 305mm Astrograph
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Wynne-Riccardi 305mm AstrographWynne-Riccardi 305mm Astrograph
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Besides its extraordinary optical design, the Riccardi Astrograph has also a very good mechanical construction and manufacturing. The system is assembled in truss tube design with carbon fibre rods. All metal parts are made of aluminium and are powder-coated. The telescope (without CCD imager) has a total length of 1m, a maximal width of 391mm and the weight is about 30kg (305mm model).

The main mirror is made of pyrex, and together with all other used materials (carbon fibre and aluminium) it provides substantially a thermo compensated system, minimizing the contraction of the material due to temperature decreases.

Telescope Blueprints

High performance CCD imaging

Wynne-Riccardi Astrograph filterholderWynne-Riccardi Astrograph filterholder
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The CCD camera is attached in prime focus on-axis right on top of the spider, which also holds the corrector. In this position the backfocus from the last corrector lens to the CCD chip is 80mm (or 79-78mm depending on the thickness of the optical window of the CCD). The spider/corrector mounting is fixed, stiff and strong enough to support filter wheels and full format CCD cameras "cantilevered" 15cm away from the corrector-lens cell.

Moreover we developed an additional adapterset that can be attached to the CCD camera. With this adapter either square or circle (depending on customer specs) filters can be integrated between the camera and the corrector. In case of any need for changing the filter, the filter could simply be removed, a new filter added, and the filter re-installed without moving neither corrector nor camera or having to recollimate.

3-element ED Wynne Corrector for optimal spot sizes

For the 305 model the diameter of the largest corrector lens measures 130mm, with a mechanical corrector assembling outside diameter of about 140mm. This is 46% of the central obstruction (true for all models). All corrector lenses are multi-coated and optimized for the visual and near infrared range (400nm to 800nm). For this range our polychromatics RMS spot diagrams show spot diameters of 4 microns (on-axis) and 6 microns at full field.

The special optical design of the system has substantially no vignetting because of the large lens diameters. E.g the 305 model.: An image circle of 52mm corresponds to a large 3.5 degrees angle with no vignetting and there's even only 8% vignetting at an image circle of 64 mm. So this Astrograph produces absolutley acceptable images up to a huge 4.2 degrees angle!

Optical diagrams

Wynne-Riccardi Astrograph spot diagramWynne-Riccardi Astrograph spot diagram
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Wynne-Riccardi Astrograph spot diagramWynne-Riccardi Astrograph spot diagram
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Wynne-Riccardi Astrograph spot diagramWynne-Riccardi Astrograph spot diagram
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Configuration and shipping

Shipping includes also a mounting plate to customers specs and a support plate for guide scopes, the collimation of the primary mirror and corrector as push pull system, a collimator tool and all needed cables, screws and tools. We provide 2 years guarantee time - delivery time: 3 to 4 months.

Overview:

Name Aperture Focal lenth Focal ratio Field Spot size
Model 305 305mm 850mm f/2.8 up to 4.2°×4.2° 4 microns (on-axis) to
8 microns (full field)
Model 406 406mm 1130mm f/2.8 3.2°×3.2°
Model 560 560mm 1400mm f/2.5 2.5°×2.5°
Model 600 600mm 1500mm f/2.5 2.3°×2.3°

Prices on request!