The Sky Rover Optics 90 SAP is a professional Petzval astrograph designed for photographing wide celestial fields with full-frame and medium-format sensors. Its 90 mm aperture, 450 mm focal length and f/5 focal ratio create a fast imaging system intended for recording extensive nebulae, large Milky Way regions and multi-panel mosaics.
The optical system consists of five air-spaced elements in a Petzval configuration. It incorporates two SD elements classified as Super ED glass, one ED element and high-refractive-index HR glass. The manufacturer describes the resulting correction as Super APO. All optical surfaces are treated with multilayer ultra-wideband anti-reflection coatings.
The integrated Petzval system provides a native flat field and does not require an additional flattener or one strictly defined corrector-to-sensor distance. The image circle has a diameter of 55 mm, allowing the telescope to support typical medium-format sensors. The manufacturer separately specifies exceptionally precise star rendering within a 44 mm field corresponding to the full-frame format.
According to the manufacturer's design data, the central RMS star-image radius is less than 1.4 µm and the geometric GEO radius is less than 2.9 µm. At the edge of the medium-format field, RMS remains below 2.2 µm, while GEO is approximately 5.8 µm. At 10 LP/mm, the MTF value remains above 0.9 up to the edge of the full-frame field, while relative illumination at its edge is approximately 98%.
The astrograph is equipped with a 3.3" aluminium Rack & Pinion focuser with dual-speed reduction and an effective travel of 38 mm. The new CAA camera angle adjuster allows the imaging train to be rotated for framing. M63 × 1, M54 × 0.75 and M48 × 0.75 interfaces are available; the manufacturer recommends M48 for APS-C and smaller sensors and M54 for full-frame sensors.
The optical tube is CNC machined from aluminium alloy. An internal knife-edge baffle is machined directly into the tube wall to help suppress stray light. The package includes dual tube rings with accessory mounting holes, a mounting plate compatible with the Vixen and Arca standards, a handle and a retractable dew shield with adjustable resistance.
• professional astrograph supporting full-frame and medium-format sensors
• 90 mm objective lens
• 450 mm focal length and f/5 focal ratio
• five-element Petzval system with a native flat field
• two SD elements classified as Super ED glass and one ED element
• high-refractive-index HR optical glass
• Super APO chromatic correction according to the manufacturer
• multilayer ultra-wideband anti-reflection coatings
• 55 mm image circle
• precisely corrected 44 mm full-frame field
• approximately 98% relative illumination at the full-frame edge
• imaging without an additional flattener or fixed corrector backfocus
• 3.3" Rack & Pinion focuser with dual-speed reduction
• CAA camera angle adjuster and three photographic thread standards
• CNC-machined aluminium tube with an integrally machined baffle
• dual tube rings, Vixen/Arca plate and handle included
• Sky Rover Optics 90 SAP OTA astrograph – 1 pc.
• tube rings – 1 set
• mounting plate compatible with the Vixen and Arca standards – 1 pc.
• carrying and accessory handle – 1 pc.
• M54 × 0.75 adapter – 1 pc.
• M48 × 0.75 adapter – 1 pc.
• hex key for adapter operation and adjustment – 1 pc.
• fitted soft carrying bag – 1 pc.
• manufacturer: Sky Rover Optics
• model: SKY ROVER 90 mm F/5 Specialist Astrograph Petzval
• series: SAP
• type: specialist Petzval astrograph
• application: astrophotography
• objective diameter: 90 mm
• focal length: 450 mm
• focal ratio: f/5
• optical design: five-element, air-spaced Petzval
• number of optical elements: 5
• number of optical groups: 5
• SD / Super ED glass: 2 elements
• ED glass: 1 element
• high-refractive-index glass: HR
• chromatic correction: Super APO according to the manufacturer
• field correction: integrated, native flat field
• optical coatings: fully multilayer, ultra-wideband
• image-circle diameter: 55 mm
• diameter of the field with declared particularly precise star correction: 44 mm
• central RMS star-image radius: below 1.4 µm
• central geometric GEO radius: below 2.9 µm
• RMS radius at the edge of the medium-format field: below 2.2 µm
• geometric GEO radius at the edge of the medium-format field: approximately 5.8 µm
• MTF at 10 LP/mm at the full-frame edge: above 0.9
• relative illumination at the full-frame edge: approximately 98%
• focuser type: 3.3" dual-speed Rack & Pinion
• effective focuser travel: 38 mm
• camera angle adjuster: CAA
• available interfaces: M63 × 1, M54 × 0.75 and M48 × 0.75
• recommended interface for APS-C and smaller sensors: M48 × 0.75
• recommended interface for full-frame sensors: M54 × 0.75
• maximum distance from M48 to the focal plane with the focuser fully retracted: 61 ± 1 mm
• maximum distance from M54 to the focal plane with the focuser fully retracted: 66 ± 1 mm
• maximum distance from M63 to the focal plane with the focuser fully retracted: 70 ± 1 mm
• optical-tube and focuser material: aluminium alloy
• optical-tube construction: precision CNC machining
• minimum length with the dew shield and focuser retracted: approximately 443 mm
• maximum length with the dew shield and focuser extended: approximately 566 mm
• mounting-plate length: 246 mm
• OTA weight: approximately 4.5 kg
• weight with rings, mounting plate and handle: approximately 5.5 kg
• SKU: 99729
The specified distances of 61, 66 and 70 mm are not required fixed corrector backfocus values but maximum distances to the focal plane with the focuser fully retracted. Sufficient focusing allowance must be retained when designing the imaging train. The 90 SAP is a specialist astrograph and, according to the manufacturer's recommendation, should not be used with visual accessories such as a diagonal and eyepieces. The camera, mount and electronic focusing motor are not included.
