Omegon Pro 2″ CLS filter
If you are looking for a reliable tool that allows you to observe the night sky even from an urban or suburban environment, the Omegon Pro CLS 2″ filter is exactly what you need. CLS (City Light Suppression) filters are among the most popular broadband filters in amateur astronomy - and the Pro series model from Omegon takes their performance a step further thanks to carefully crafted optical surfaces and a precision aluminium thread.
How the filter works
The filter operates on the principle of selective light transmission. It passes the wavelengths characteristic of astronomically interesting objects - particularly the OIII oxygen emission band and the hydrogen H-beta line - while effectively blocking the unwanted spectral lines of sodium and mercury vapour lamps that are the main source of light pollution in urban and suburban areas.
The result is a noticeably darker sky background and improved contrast of observed objects, whether you are observing visually at the eyepiece or capturing images with a CCD or CMOS camera. The filter is suitable for observers of all experience levels who want to get the most out of their local observing conditions.
What the filter is best suited for
The Omegon Pro CLS is particularly effective when observing planetary nebulae, where suppressing light pollution makes a visible difference even to the naked eye at the eyepiece. The filter is also well suited as an astrophotography filter, helping to reduce effective exposure times and minimise the background gradient caused by light pollution.
It is worth noting that this filter is not primarily designed for the following targets:
- Hydrogen emission nebulae (narrowband H-alpha filters are better suited for these)
- Comets
- Central stars of nebulae
- Supernova remnants
Construction and compatibility
The filter is housed in a precision-machined aluminium body with a standard 2″ thread, compatible with standard focuser drawtubes and screw-on adapters. The Pro series from Omegon places strong emphasis on optical quality - anti-reflection coatings on the filter glass minimise unwanted internal reflections and ensure that light passes through with minimal loss of brightness.
Installation is straightforward: simply screw the filter into the focuser drawtube before inserting the eyepiece or camera nosepiece.
Key specifications
| Parameter |
Value |
| Filter size |
2″ |
| Filter type |
CLS (City Light Suppression) - broadband |
| Thread |
Standard 2″ aluminium thread |
| Passed wavelengths |
OIII, H-beta |
| Blocked wavelengths |
Sodium and mercury vapour lamp emission lines |
| Suitable for |
Visual observation and CCD/CMOS astrophotography |
Summary
The Omegon Pro 2″ CLS filter is a practical and affordable choice for any amateur astronomer looking to combat light pollution - whether you are observing at the eyepiece or controlling a camera from your backyard observatory. It is the kind of filter that, after the first use, will permanently find its place in your accessory bag.
