Explore Scientific UHC 2″ filter
Light pollution is one of the greatest enemies of the modern amateur astronomer. The glow of street lamps and urban infrastructure means that the night sky around towns and cities is never truly dark. For many types of objects this severely limits observability - sometimes reducing it to zero. The good news, however, is that emission nebulae radiate light at very specific wavelengths, and a well-designed filter can make excellent use of that fact.
How the UHC filter works
The Explore Scientific UHC (Ultra High Contrast) filter is designed to transmit only narrow wavelength bands corresponding to the emission lines of two key elements - hydrogen and oxygen. Specifically, these are the H-beta line (486 nm), the H-alpha line (656 nm), and the pair of OIII oxygen lines (496 nm and 501 nm). All other wavelengths - including those emitted by the sodium and mercury vapour lamps typical of street lighting - are effectively blocked. The result is a dramatic increase in the contrast of a nebula against the sky background. An object that was invisible without the filter suddenly appears with striking clarity.
What you can observe with this filter
The difference is best illustrated with specific examples. The Owl Nebula (M97) and the sprawling supernova remnant known as the Veil Nebula (NGC 6992) are very difficult or completely invisible on a suburban sky without a filter. With the UHC filter, however, these objects reveal surprisingly rich detail and clear contrast. Even the popular Dumbbell Nebula (M27), one of the brightest planetary nebulae in the sky, gains in depth and definition when viewed through this filter. The filter is equally beneficial under a genuinely dark sky, where it further enhances the delicate structure of large emission regions.
Compatibility and usage
The light pollution filter of this type is today an indispensable part of every visual deep-sky observer's equipment. The filter is intended for visual observation and fits any eyepiece with a standard 2″ thread. Thanks to its standard threaded design, it can be easily moved between eyepieces or used in combination with a 2″ to 1.25″ reduction adapter.
Individual test certificate included
Every Explore Scientific UHC filter is supplied with an individual test certificate documenting the precise optical parameters of that specific unit. This is not a general quality declaration for the entire production batch - it is a measurement of your filter. That is a standard that is by no means a given in this price category, and it clearly reflects the approach of the Explore Scientific brand to manufacturing quality.
Summary
If you are looking for a reliable and technically precise instrument that allows observation of emission nebulae even from less-than-ideal conditions, the Explore Scientific UHC 2″ filter is a choice that will not disappoint you - quite the opposite.
Key specifications
| Parameter |
Value |
| Filter type |
UHC - Ultra High Contrast |
| Thread size |
2″ |
| Transmitted wavelengths |
H-beta 486 nm, OIII 496 nm and 501 nm, H-alpha 656 nm |
| Intended use |
Visual observation of emission and planetary nebulae |
| Compatibility |
Any 2″ eyepiece; usable with 2″ to 1.25″ adapter |
| Certificate |
Individual test certificate included |
