The Dark Clear Skies M68M to M63F Fine Back Focus Spacer (1.4 mm) is a precision-machined spacer designed for fine adjustment of back-focus distance in large-format astrophotography imaging trains.

Purpose & Use

Many modern reducers, flatteners, and imaging systems that use larger thread standards such as M68 and M63 require extremely precise back-focus spacing to deliver optimal star shapes across the image field. Even small spacing errors of around 1 mm can noticeably affect edge correction.

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
• M63 × 1 female thread on camera-side component
• CNC-machined aluminium construction
• Matte black internal finish to minimise reflections
• Low-profile, rigid design for large-format 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 in conjunction with existing spacers or adapters where small spacing corrections are required.

Compatibility

This spacer is designed for astrophotography imaging trains that use M68 and M63 thread interfaces. It is commonly used with reducers, flatteners, filter wheels, and cameras designed for larger sensors where precise spacing is critical.

Typical Applications

• Fine tuning reducer or flattener back-focus spacing
• Correcting edge star distortion on APS-C and full-frame sensors
• 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.