Skip to content
IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
Lunt B1800 Blocking Filter
Lunt B1800 Blocking Filter
Lunt B1800 Blocking Filter
Lunt B1800 Blocking Filter

Lunt B1800 Blocking Filter

by Lunt Solar Systems
SKU LSS-B1800s
$795.00 - $795.00
$795.00
$795.00 - $795.00
$795.00
Price Match Policy!
  • Required safety component for all Lunt Solar Systems H-alpha etalons
  • Sized for longer focal length telescopes to prevent vignetting
  • Available in 1.25" and 2" star diagonal housings for visual comfort
  • Available in a 2" straight-through housing for imaging applications
  • Features integrated T2 threads for secure camera attachment on all models
Backordered
Request Stock Alert
Availability Info
FREE Shipping in CONUS
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • Lunt B1800 Blocking Filter

    Available in 1.25" and 2" formats, the Lunt B1800 Blocking Filter is a critical safety component for all Lunt H-alpha etalon systems and is specifically sized to prevent vignetting in telescopes with longer focal lengths. The B1800 is offered in multiple housings, including a 2" straight-through tube and both 1.25" and 2" star diagonals, all of which incorporate a T2 thread for secure camera connections.

    The Lunt B1800: A Critical Safety Component in 1.25" and 2" Formats

    A Lunt blocking filter is not an optional accessory; it is an essential part of the complete solar telescope system. The housing contains additional, specialized filters that work in conjunction with the main etalon to reject harmful radiation and provide a safe, high-contrast view of the Sun's chromosphere. Lunt Solar Systems can only warranty the safety and optical performance of their H-alpha systems when used with a matching Lunt blocking filter.

    Sizing the B1800: Matching Filter Aperture to Telescope Focal Length

    The "B1800" designation indicates this blocking filter is designed for telescopes with longer focal lengths. As a telescope's focal length increases, the light cone it produces becomes longer and narrower, requiring a larger blocking filter aperture at the focal plane to intercept the entire field of view without vignetting. The B1800 ensures that the full solar disk remains illuminated, which is crucial for both visual observation and imaging.

    For imaging, it is recommended to choose a larger blocking filter than required for visual use with the same telescope. The added back focus of a camera setup moves the sensor further down the optical path, where the light cone is wider. The B1800 provides the necessary aperture to accommodate this wider cone, preventing the edges of your images from being clipped or darkened.

    Housing & Connectivity: T2 Threads on All 3 B1800 Configurations

    The Lunt B1800 is available in three distinct configurations to match your equipment and observing style. Your choice of housing does not affect the filter's performance but determines its physical connection to your telescope and eyepieces.

    • Diagonal Housings (1.25" or 2"): These are the standard choice for visual observing, providing a comfortable 90-degree viewing angle. The choice between a 1.25" and 2" model depends on your focuser and eyepiece collection.
    • Straight-Through Housing (2"): This version is optimized for astrophotography. It provides a direct, rigid optical path to the camera sensor, minimizing potential flexure and making it easier to achieve perfect focus.
    • T2 Threads: All three versions come standard with male T2 (M42x0.75) threads, allowing you to connect most dedicated astronomy cameras directly and securely to the blocking filter.

  • Why is the Lunt B1800 Blocking Filter required for my Lunt solar telescope?

    The Lunt B1800 is a mandatory safety component. It contains a set of secondary filters that work with your main etalon to remove harmful out-of-band radiation, making it safe to view the Sun. It is not just a simple diagonal or adapter; it is an integral part of the telescope's filtering system, and Lunt only warranties safety and performance when their etalons and blocking filters are used together.

    How do I know if the Lunt B1800 is the right size for my telescope?

    The correct blocking filter size is determined by your telescope's focal length. The Lunt B1800 is designed for telescopes with longer focal lengths. Using a filter that is too small for your telescope's focal length will result in vignetting, where the edges of the Sun's disk are cut off. If you plan to image, it's always recommended to select the next larger blocking filter than what is suggested for visual use alone.

    Should I get the diagonal or straight-through version of the Lunt B1800 Blocking Filter?

    Choose the housing based on your primary use. For visual observing, a diagonal housing (either 1.25" or 2") provides a much more comfortable viewing angle. For astrophotography, the 2" straight-through housing provides the most rigid and direct connection for your camera, which helps prevent flexure and maintain focus.

    I want to image the Sun with my 1200mm refractor. Is the Lunt B1800 a better choice than the B1200?

    Yes, for imaging, the Lunt B1800 is the superior choice for a 1200mm focal length telescope. While a B1200 would work for visual use, imaging systems require more back focus. This moves the camera sensor further from the focal plane, intersecting a wider part of the light cone. The larger aperture of the B1800 is necessary to illuminate the entire camera sensor without vignetting.

    Can I use the Lunt B1800 Blocking Filter for visual observing in my 8" SCT?

    Yes, the Lunt B1800 is an excellent match for a typical 8" Schmidt-Cassegrain Telescope (SCT). These telescopes usually have a focal length around 2000mm, which requires a larger blocking filter like the B1800 to fully illuminate the field of view for visual observation of solar prominences and surface detail.

    What is the T2 thread on the Lunt B1800 Blocking Filter for?

    The T2 (M42x0.75) thread is an industry standard for astrophotography. It allows you to attach a dedicated astronomy camera, DSLR with a T-ring, or other imaging accessories directly to the Lunt B1800 Blocking Filter. This creates a secure, threaded connection that is far more stable than using a simple set screw in an eyepiece holder.

  • SKU B400
    Available Options 2" in Straight Thru 2" tube with T2 & 2" connection, 1.25" in star diagonal with T2 connection, 2" in star diagonal with T2 connection
  • Lunt Solar Systems 5-Year Warranty