Why is the Lunt B1800 Blocking Filter required for my Lunt solar telescope?
The Lunt B1800 is a mandatory safety component. It houses additional filters which are required for the safety and performance of the solar package. 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 blocking filter further up the light cone, where the cone is larger. 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?
No. The B1800 is suggested for visual use on telescopes with focal lengths up to 1800 mm, and a typical 8" Schmidt-Cassegrain Telescope (SCT) has a longer focal length. A blocking filter is never a solar filter on its own: Lunt can only warranty safety or performance when one of its blocking filters is paired with a Lunt H-alpha filter or telescope.
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.
