Lunt BF1800S 1.25/2 Extension Tube

Lunt BF1800S 1.25/2 Extension Tube

Description
The Lunt BF1800S blocking filter in a 1.25"/2" extension tube is an essential part of a safe and complete solar observing system. Used in combination with a front-mounted etalon filter, it ensures the suppression of UV, IR, and out-of-band light, protecting the observer’s vision or imaging sensor.

Unlike diagonal versions, this straight-through model is designed for configurations that do not require an angled view. It is especially well-suited for camera-based solar imaging or direct viewing with straight focusers.

With an 18 mm clear aperture, the filter supports refractors with focal lengths up to approximately 1620 mm. The rear end offers both a T2 thread and 1.25" eyepiece compatibility, enabling flexible and secure connections.

Technical specifications
• Product reference: 0553011
• EAN: 4007922035857
• Clear aperture: 18 mm
• Format: 1.25"/2" straight extension tube
• Central wavelength: H-alpha 656.28 nm
• Use: Visual and solar imaging
• Telescope compatibility: up to 1620 mm focal length
• Connections: T2 thread and 1.25" barrel
• Housing: Black anodized aluminum

User benefits
• Full protection from harmful wavelengths
• Straight-through format ideal for cameras or direct viewing
• Compatible with all Lunt front H-alpha filters
• Robust and compact build
• T2 threading for direct image train integration

Additional information
• Must always be paired with a Lunt front etalon
• Not a standalone solar filter
• Suitable for advanced or professional users
• Ideal for chromospheric solar detail capture