Optolong Clear Focusing Filter Optolong Clear focusing filter is designed to highly pass the visible spectral region 420-680nm at 98.5% transmission. Main Use Use of astrophotography filters, especially narrowband filters, often results in dim images which can be difficult to focus. Clear focusing filter can be used first to clearly focus the image. Use with modified DSLRs for higher efficiency and sensitivity by passing visible range with 98.5% transmission. Act as an outstanding dust shield, which prevents the possibility of dust settling on the lens during long time exposure. WARNING: The filters of Optolong are not designed for sun observation. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTER. You would be BLIND if you fail to observe the warning. Technical Specifications Sbustrate: B270Thickness: 1.85mmTave: T>98.5%Surface quality: 60/40Transmitted Wavefront RMS: λ/4Parallelism: 30s How to read the chart? ▲The horizontal axis is the Wavelength in Nanometers(nm). ▲The vertical axis is transmission in %. In the Box Filter Manual & Warranty
