Optolong Clear focusing filter 2"

Clear Focusing Filter Introduction

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.

Clear Focusing Filter Spectrum and Characteristic
Sbustrate: B270
Thickness: 1.85mm
Tave: T>98.5%
Surface quality: 60/40
Transmitted Wavefront RMS: λ/4
Parallelism: 30s