The Dark Clear Skies M68M to M54F Fine Back Focus Spacer (1.4 mm) is a precision-machined spacer designed for fine adjustment of back-focus distance in astrophotography imaging trains.

Purpose & Use

Many modern reducers and field flatteners require extremely precise back-focus spacing to deliver optimal star shapes and edge correction, particularly when used with larger sensors. Even small spacing errors of around 1 mm can noticeably affect image quality.

This spacer provides a fixed mechanical thickness of 1.4 mm and is intended for fine back-focus correction once the primary spacing has already been established.

Key Features

• Fixed 1.4 mm mechanical spacing for fine back-focus adjustment
• M68 × 0.75 male thread on telescope side
• M54 × 0.75 female thread on camera-side component
• CNC-machined aluminium construction
• Matte black internal finish to minimise internal reflections
• Low-profile, rigid design for imaging trains

Important Usage Note

This spacer is intended for fine back-focus adjustment only. It is not suitable for building primary spacing distances and should be used alongside existing spacers or adapters where small spacing corrections are required.

Compatibility

This spacer is designed for astrophotography imaging trains that use M68 and M54 thread interfaces. It is commonly used with reducers, flatteners, filter wheels, and camera adapters where precise spacing control is required.

Typical Applications

• Fine tuning reducer or flattener back-focus spacing
• Correcting edge star distortion caused by spacing errors
• Adjusting imaging trains after adding filters or accessories
• Large-format astrophotography and EAA setups

Technical Specifications

If you are unsure whether a 1.4 mm spacer is required for your optical system, feel free to contact us for guidance before purchase.