12mm Blocking Filter Aperture Required safety component for all Lunt H-alpha Etalon systems Available in 1.25" or 2" diagonal housings Available in a 2" straight-through housing for imaging Includes T2 threads for secure camera connection Description FAQ Specifications In the Box Downloads Warranty Lunt B1200 Blocking Filter The Lunt B1200 Blocking Filter integrates a 12mm aperture with essential, non-removable safety filters, making it a mandatory component for any Lunt H-alpha solar telescope or Etalon filter system. Available in 1.25" or 2" diagonal housings for visual comfort, as well as a 2" straight-through option for imaging, the B1200 is designed to prevent vignetting in telescopes with moderate to long focal lengths. This 12mm filter size ensures the entire solar disc is illuminated at the focal plane and is the recommended minimum for most imaging applications. The 12mm Blocking Filter's Role in a Lunt H-alpha System A Lunt blocking filter is not an optional accessory; it is an integral part of the solar filtering system that is absolutely required for safe observation. The B1200's housing contains a unique, multi-filter stack that works in conjunction with the front-mounted Etalon to reject harmful radiation and isolate the H-alpha wavelength. Lunt Solar Systems can only warranty the safety and optical performance of their systems when a Lunt Etalon is paired with a matching Lunt blocking filter. Sizing and Application: Why a 12mm Aperture is Critical for Imaging Choosing the correct blocking filter is determined by your telescope's focal length and your intended application. The 12mm aperture of the B1200 is sized to fully illuminate the field in telescopes with longer focal lengths, preventing the edge of the solar disk from being cut off. For imagers, the B1200 is often the necessary choice even on shorter scopes, as imaging trains require additional back focus. This moves the filter further from the focal plane, where the light cone is wider, demanding the larger 12mm aperture to avoid vignetting your camera sensor. Choosing Between 1.25" Diagonal, 2" Diagonal, or 2" Straight-Through Housings The Lunt B1200 is available in three distinct housings to match your equipment and observing style, with all versions including an integrated T2 thread for direct camera attachment. Diagonal Housings (1.25" or 2"): These are the standard choice for visual observing, placing the eyepiece at a comfortable 90-degree angle. Choose the barrel size that matches your eyepieces and focuser. Straight-Through Housing (2"): This configuration is purpose-built for astro-imaging. It provides a direct, non-deflected light path to the camera sensor, which is critical for minimizing tilt and ensuring the sharpest possible image across the entire field. Why is the Lunt B1200 Blocking Filter required for my Lunt Etalon? The Lunt B1200 is a critical safety component. It contains secondary filters that work with the main Etalon to block harmful UV and IR radiation, making solar observation safe. Its use is mandatory for the proper and safe functioning of any Lunt H-alpha system, and is required for warranty coverage. Should I choose the Lunt B1200 or a smaller blocking filter like the B600? The choice depends on your telescope's focal length and whether you plan to do visual observing or imaging. The Lunt B1200 is designed for telescopes with longer focal lengths to prevent the edges of the Sun's disc from being cut off. It is also the recommended starting point for imaging, as camera sensors require more back focus, which in turn requires a larger blocking filter aperture to avoid vignetting. I want to image the Sun with my 1200mm focal length refractor. Is the Lunt B1200 correct? Yes, the Lunt B1200 is an excellent choice for a telescope with a 1200mm focal length, especially for imaging. The 12mm aperture is large enough to accommodate the wider light cone associated with both the long focal length and the increased back focus needed for a camera, ensuring your sensor is fully illuminated. What is the difference between the diagonal and straight-through versions of the Lunt B1200? The diagonal housings (1.25" and 2") are primarily for visual use, providing a comfortable 90-degree viewing angle. The 2" straight-through housing is designed for imaging, as it provides a direct light path to the camera sensor, which helps to eliminate potential optical tilt and ensures the highest image fidelity. Can I use the Lunt B1200 to see a full-disc view of the Sun in my Lunt LS80THa telescope? Absolutely. The Lunt B1200's 12mm aperture is more than sufficient to provide a complete, unvignetted view of the entire solar disc when used visually with a Lunt LS80THa or other telescopes with similar focal lengths. It provides a generous field of view for framing the Sun and surrounding prominences. Do all versions of the Lunt B1200 Blocking Filter have a T2 thread for my astronomy camera? Yes, all available housing options for the Lunt B1200—the 1.25" diagonal, 2" diagonal, and 2" straight-through tube—come standard with a T2 connection. This allows you to securely thread your camera directly to the blocking filter for imaging. Aperture 12mm Available Housings 2" Straight-Through Tube, 1.25" Star Diagonal, 2" Star Diagonal Camera Connection T2 Thread (on all housing options) Eyepiece/Focuser Connection 1.25" or 2" (depending on housing option) Lunt B1200 Blocking Filter Assembly × 1 Lunt Solar Systems 5-Year Warranty
