{"id":109397,"date":"2026-07-16T16:56:21","date_gmt":"2026-07-16T14:56:21","guid":{"rendered":"https:\/\/www.telescoop.nl\/lunt-b1800d2-blockfilter-in-zenitspiegel-2-inch\/"},"modified":"2026-07-20T17:07:23","modified_gmt":"2026-07-20T15:07:23","slug":"lunt-b1800d2-block-filter-in-zenith-mirror-2-inch","status":"publish","type":"product","link":"https:\/\/www.telescoop.nl\/en\/lunt-b1800d2-blockfilter-in-zenitspiegel-2-inch\/","title":{"rendered":"Lunt B1800d2 Blocking Filter in 2-inch diagonal mirror"},"content":{"rendered":"

A blockfilter<\/strong> is not an accessory that you can buy with it, it is a necessary part<\/em> of each H-alpha system. The etalon at the front allows the H-alpha line to pass through, as well as its harmonics. The blocking filter is located just before the eyepiece and removes all this remaining light. Without a blocking filter, the system is not safe<\/strong>.<\/p>\n\n\n\n

\"Lunt<\/figure>\n\n\n\n

The number is the pass<\/h3>\n\n\n\n

B600, B1200, B1800, B3400: the number indicates the free passage in tenths of millimeters. A B1200 has a 12 mm passage.<\/strong>. The larger the aperture, the larger the portion of the field of view that unobstructed and uniformly illuminated<\/em> and the longer the focal length you can use without vignetting.<\/p>\n\n\n\n

Rule of thumb: for visual use<\/strong> is a smaller block filter sufficient. For photography<\/strong> Your sensor size determines the choice. Small sensor: B1200 can. APS-C: B1800. Large sensor or full-frame: B3400.<\/p>\n\n\n\n

This version: 18mm in zenith mirror (2 inch)<\/h3>\n\n\n\n

Passage 18 mm<\/strong>, suitable for telescopes to 1620 mm focal length<\/strong>. Execution: Zenith mirror (2 inch). At the eyepiece side 1.25 inch with T2 thread for camera connection.<\/p>\n\n\n\n

The B1800 is the recommended choice for photography with APS-C sensors<\/strong> and for visual use with widefield eyepieces.<\/p>\n\n\n\n

Notice:<\/strong> This filter does not work independently. It is only usable in combination with a Lunt H-alpha telescope or filter system.<\/p>\n\n\n\n

Specifications<\/h2>\n\n\n\n