Star Diagonals

A star diagonal is an angled mirror or prism used in telescopes that allows viewing from a direction that is perpendicular to the usual eyepiece axis. It allows more convenient and comfortable viewing when the telescope is pointed at, or near the zenith (i.e. directly overhead). Also, the resulting image is right side up, but is reversed from left to right. Star diagonals are available in 1.25" and 2" diameters. The 2" diagonals allow larger longer focal length low power 2 inch barrel eyepieces for a greater field of view. Star diagonals come in all price ranges. However , even an expensive star diagonal will deliver poor performance if it is not in alignment with the optical axis of the telescope. A telescope in perfect collimation will be thrown out of collimation by a misaligned star diagonal and often this misalignment will determine the image quality of the telescope to a larger extent than the surface accuracy of the prism or mirror. Since the mirror or prism of the star diagonal is located nearly at the focal plane of the instrument, surface accuracy of greater that 1/4 wave is more in the line of advertising than any increase in optical performance. A 1/10 wave mirror or prism star diagonal that throws off the collimation of the telescope will perform worse than a 1/2 wave star diagonal that is in proper alignment.



Product Image Item Name+ Price
(SPECIAL) 2" Durabright CF 2" Dielectric Diagonal

(SPECIAL) 2" Durabright CF 2" Dielectric Diagonal

(SPECIAL) 2" Durabright CF 2" Dielectric Diagonal Ultra High Dielectric 99% reflectivity. Precision 1/15 lambda surface with NEW (15mm...
R2,645.00

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Baader Planetarium 32mm Prism Diagonal T-2/90

Baader Planetarium 32mm Prism Diagonal T-2/90

Baader Planetarium 32mm Prism Diagonal T-2/90 The diagonal has a clear aperture of 32mm - more than normal 1.25" diagonals. Please enquire when...
R1,725.00

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Baader Planetarium 32mm Prism Diagonal T-2/90 Set

Baader Planetarium 32mm Prism Diagonal T-2/90 Set

Baader Planetarium 32mm Prism Diagonal T-2/90 Set The set contains T-2/32 Diagonal with focusing 1.25" eyepiece clamp and 1.25" nose...
R2,075.00

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GSO 1.25" 90 Mirror Star Diagonal for Refractors

GSO 1.25" 90 Mirror Star Diagonal for Refractors

GSO 1.25" 90 mirror star diagonal for refractors. Features: Al + SiO2 coatings1/10 Wave mirror92% Reflectivity across the spectrumTwo end caps...
R675.00

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GSO 2" Dielectric Star Diagonal

GSO 2" Dielectric Star Diagonal

1095 GSO 2" Dielectric Star diagonal. Features: Mirror 1/12 wave99% Reflectivity Please enquire when stock is indicated as zero. Availability...
R2,645.00

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GSO 2" Mirror Diagonal

GSO 2" Mirror Diagonal

GSO 2" Mirror diagonal. 1/10 wave Features: Includes 1.25" adaptorMirror 1/10 wave92% Reflectivit This product is in stock. Please enquire...
R1,325.00

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GSO 2" Quartz Diagonal

GSO 2" Quartz Diagonal

GSO 2" Star diagonal. Features: Quartz 1/12 wave99% Reflectivity Please enquire when stock is indicated as zero. Availability is typically...
R3,175.00

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Orion 1.25" 90 Enhanced Mirror Star Diagonal

Orion 1.25" 90 Enhanced Mirror Star Diagonal

Orion 1.25" 90o Enhanced mirror star diagonal. Features: For use on a high-quality refractor or CassegrainReflect 97% of the inbound light to...
R1,195.00

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Orion 1.25" 90 Prism Star Diagonal

Orion 1.25" 90 Prism Star Diagonal

Orion 1.25" 90 Prism star diagonal. Features : For astronomical useThis diagonal produces an image that's right-side-up, reversed left to...
R595.00

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Orion 1.25" Erect Image Star Diagonal

Orion 1.25" Erect Image Star Diagonal

Orion 1.25" Erect Image Star Diagonal For terrestrial or astronomical use, this1.25" 90 diagonal produces a right-side-up, nonreversed...
R875.00

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