Clear focusing filter is designed to highly pass the visible spectral region 420-680nm at 98.5% transmission

Optolong Clear focusing filter is designed to highly pass the visible spectral region 420-680nm at 98.5% transmission

1.  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.
 
2. 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
 
How to read the chart?
▲The horizontal axis is the Wavelength in Nanometers(nm).
▲The vertical axis is transmission in %.

3. Coating Technology
·Multi-layers anti-reflection coating
·Non-cementing optical substrate coating
·Optolong L-Pro filter adopts precision coating based on Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL(central wavelength) no deviation affected by temperature change.
·Planetary rotation system offers precision and homogeneity of coatings ensuring high value on transmission of pass-band and Optical density of off-band.
 
5. Packing
Outer Box: silve box
Plastic Box: PP material
Lining: imported high pressure white EVA material