Ritchey - Chretien 250mm

Availability: Product sold-out Type: reflector

Our Ritchey-Chrétien reflector series is engineered for uncompromising imaging performance.
Each unit integrates all essential components into a precision-crafted package featuring hand-figured optics, premium mechanical construction, and a durable, long-lasting finish.
We offer a selection of optical substrates to suit a range of performance needs and budgets:

Supremax33 Borosilicate Glass (Schott) – Fine-annealed and cost-effective, ideal for entry-level applications.
Fused Silica / Quartz (Ohara's SK-1300) – Ultra Low Expansion (ULE) material with excellent thermal stability.
Clearceram-HS (Ohara) – glass ceramic material with ultimate level of thermal stability.

For apertures of 350 mm and above, we strongly recommend Fused Silica / Quartz or Clearceram-HS, both of which deliver superior thermal behaviour and exceptional optical surface quality.

Key features:
* Hand-figured Ritchey - Chretien optics
* Precision adjustment of primary & secondary mirror
* Portable, medium size reflector telescope
* Truss type chassis design for stability and quick cool down times.
* Carbon fibre and aluminium alloy, high quality chassis/frame.

Specifications & technical data:
Clear aperture – 250 mm; Focal ratio – F/7; Focal length – 1750 mm; Central Obstruction – 50%, linear
Clear aperture – 250 mm; Focal ratio – F/8; Focal length – 2000 mm; Central Obstruction – 52%, linear
Primary substrate – Supremax33, Fused Silica/Quartz, Clearceram HS.
Secondary substrate – Supremax33, Fused Silica/Quartz, Clearceram-HS.

Dimensions:
F/7 version – 750 x 345 x 380 mm (L x W x H)
F/8 version – 800 x 345 x 380 mm (L x W x H)
Weight = ~13 kg*
Usable back-focus = ~235 mm*, from back-plate
Usable back-focus = ~104.7 mm*, from corrector's last mechanical surface, at F/7
Usable back-focus = ~98.5 mm*, from corrector's last mechanical surface, at F/8.
*Variations may occur with individually produced components.

Pricing:
Product unavailable for ordering in its legacy specification, with in-house made optics.
We offer an identical product based on Ritchey-Chretien 250mm F/8 optical sets manufactured by GSO, in Taiwan.

Included items:
– 3.2" Starlight Instruments focuser, rack and pinion, 38mm travel
– Field Corrector, 44mm corrected circle diameter
– shroud pack (secondary casing shroud, secondary cage shroud, truss shroud)
– side plates (pair)
– riser + finder shoe (Starlight FSB-CH)
– primary mirror cooling fans
– primary mirror heater
– primary mirror hard cover
– secondary mirror heater
– 350 mm D-type dovetail
– handle.

Coatings:
standard coating reflectance: 92% (SiO overcoat), included in the price.

Optional accessories to consider when ordering:
Additional dovetail, Losmandy Type, 350 mm length, lightweight, to replace the handle.
Controller for heaters and fans (several variants available for integration).
Electronic focusing package for FTF3215.
Motorized Flat Panel cover.

Visual accessories:
A prism or mirror diagonal will be needed, together with good quality eyepieces, to be able to extract the most of your new telescope.

Imaging accessories:
Adapter rings are available to fit the thread dimensions of each supplied corrector.

Number of units manufactured with in-house made optics: 17

* Prices subject to change without notice.
* Net prices are exclusive of any applicable duties and taxes.
These are the responsibility of the Buyer and may be charged by your local customs authority upon delivery.

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