Sightron Japan SJH-75UF Ultra-Flat Field Astrograph

The Sightron Japan SJH-75UF is a premium 75mm f/5 ultra-flat field astrograph, designed and manufactured in Japan for astrophotographers seeking exceptional sharpness, field correction and optical performance. Built around an advanced six-element, six-group optical system incorporating two SD glass elements and one ED glass element, the SJH-75UF represents Sightron Japan's flagship approach to precision astronomical optics.

Developed by experienced Japanese optical engineers, including engineers involved in the development of renowned Japanese telescope designs, the SJH-75UF has been engineered around one fundamental objective: producing exceptionally tight, point-like stars across the entire imaging field.

Final assembly and quality inspection are carried out at Sightron Japan's Niigata Tainai Factory in Tainai City, Niigata Prefecture, Japan, where each telescope is individually assembled and inspected by experienced optical craftspeople before shipment.

Japanese-Designed Ultra-Flat Field Optics

At the heart of the SJH-75UF is an entirely new ultra-flat field optical design developed to minimise aberrations across a full-frame imaging sensor.

Its sophisticated six-element, six-group configuration includes two SD glass elements and one ED (Extra-low Dispersion) glass element, providing excellent chromatic correction and extremely fine star reproduction.

The optical design targets a calculated spot diameter of approximately 0.67μm on-axis and 1.31μm at the edge of a full-frame sensor. These design values are significantly smaller than the diffraction-limited Airy disk, demonstrating the emphasis placed on achieving precise point-like stars from the centre to the outer edges of the image.

75mm Aperture and Fast f/5 Performance

With a 75mm aperture and 375mm focal length, the SJH-75UF operates at f/5, providing a versatile combination of field of view, resolution and light-gathering performance.

The 375mm focal length is particularly well suited to photographing large nebulae, open star clusters and expansive regions of the Milky Way. Its high-resolution optical design also makes it suitable for modern cameras with small CMOS pixels.

The f/5 focal ratio provides a useful balance between imaging speed and filter compatibility, reducing some of the challenges very fast optical systems can encounter with interference and narrowband filters.

44mm Full-Frame Image Circle

The 44mm image circle is designed to accommodate full-frame astronomy cameras and DSLRs while maintaining excellent optical performance across the field.

A large-diameter rear optical element helps provide approximately 90% illumination at the outer edge of the image circle, reducing vignetting and helping maintain cleaner, more consistent star shapes towards the corners of the frame.

ULR Ultra-Low Reflection Coatings

All lens surfaces feature ULR (Ultra Low Reflection) coatings designed to minimise unwanted reflections and maximise light transmission. These coatings help suppress flare and ghosting while improving image contrast.

Advanced Internal Reflection Control

Selected lens spacing and light-shielding components use special low-reflection anodised aluminium, engineered to suppress reflections across visible and near-infrared wavelengths more effectively than conventional anodised surfaces.

The durable anodised oxide layer is also designed to maintain its optical characteristics over extended use.

Precision Dual-Speed Rack-and-Pinion Focuser

The SJH-75UF features a dual-speed rack-and-pinion focuser engineered to provide accurate focusing for demanding astrophotography.

A bearing rail guide provides additional support for the drawtube, helping maintain precise positioning when heavier astronomy cameras and imaging accessories are installed.

An M4 mounting hole beneath the focus knob also provides compatibility with many third-party electronic and motorised focusing systems.

Integrated 360° Camera Rotation

A built-in 360-degree rotator allows the camera orientation to be adjusted without dismantling the imaging train. This makes it easy to fine-tune image composition while retaining accessories such as filter wheels and off-axis guiders.

Retractable and Lockable Dew Shield

For easier transportation and storage, the SJH-75UF features a retractable dew shield. When extended, the hood can be securely fixed in position using its threaded locking mechanism, helping prevent unwanted movement during an imaging session.

Flexible Camera, Eyepiece and Filter Connectivity

The SJH-75UF supports a broad range of visual and astrophotography configurations, including 2-inch (50.8mm) and 1.25-inch (31.7mm) accessories as well as M48 × 0.75 connections.

The adapter also supports M48 × 0.75 and M52 × 0.75 filters, providing additional flexibility when configuring an imaging system.

Complete Mounting Hardware Included

The SJH-75UF includes telescope tube rings, a 45mm-wide dovetail bar, top mounting plate and finder scope mount, providing a solid foundation for building a complete astrophotography setup.

Made in Japan

One of the defining characteristics of the Sightron Japan SJH-75UF is its Japanese manufacturing and quality-control process.

Assembly and final quality inspection take place at the Sightron Japan Niigata Tainai Factory in Tainai City, Niigata Prefecture, Japan. Each telescope is carefully assembled by experienced craftspeople with extensive backgrounds in optical manufacturing and must satisfy Sightron Japan's strict quality standards before being approved for shipment.

For astrophotographers who value Japanese optical engineering, precision manufacturing and rigorous quality control, the SJH-75UF represents a distinctly Japanese approach to premium telescope construction.

5-Year Manufacturer Warranty

The SJH-75UF is backed by a 5-year manufacturer's warranty, providing long-term confidence in its Japanese assembly and construction. Qualifying faults occurring during normal use in accordance with the manufacturer's operating instructions are covered under the applicable warranty conditions.

Main Specifications

Key Features

Designed and manufactured in Japan
Final assembly and inspection at Sightron Japan's Niigata Tainai Factory
75mm aperture and 375mm focal length
Fast f/5 focal ratio
Six-element, six-group ultra-flat field optical design
Two SD glass elements and one ED glass element
44mm image circle for full-frame cameras
Approximately 90% peripheral illumination at the edge of the image circle
ULR Ultra Low Reflection lens coatings
Special low-reflection internal anodising
Dual-speed rack-and-pinion focuser
Motorised focuser compatibility
Integrated 360° camera rotator
Retractable and lockable dew shield
2-inch and 1.25-inch accessory compatibility
M48 and M52 filter compatibility
Tube rings, dovetail bar, top plate and finder mount included
5-year manufacturer's warranty