The Astronomik UHC-E filter is tailored for deep-sky observation of emission nebulae and comets under light-polluted skies, especially ideal for smaller telescopes up to 5" (125mm) aperture. It enhances the contrast between these celestial objects and the sky background by blocking typical streetlight and LED lamp emissions, as well as all lines of natural airglow.With a Full-Width-Half Maximum (FWHM) of 45nm, the Astronomik UHC-E filter ensures a significant contrast boost while allowing a greater amount of starlight to pass through compared to its counterpart, the Astronomik UHC filter. This characteristic makes it particularly well-suited for smaller telescopes, enhancing visibility without compromising on the overall brightness. Additionally, its transmission range includes spectral lines, enhancing the observation of comets.In essence, the Astronomik UHC-E filter is a versatile tool for enhancing contrast under urban sky conditions, especially for observers using smaller telescopes to explore the depths of deep-sky objects and comets.Alternatives For telescopes larger than 5" (125mm), we recommend upgrading to the standard Astronomik UHC filter, which provides even greater contrast enhancement capabilities. For telescopes exceeding 8" (200mm), we suggest an Astronomik OIII visual filter as first filter.Suitability of the Astronomik UHC-E filtersVisual observation (dark skies): Reasonable, an Astronomik UHC filter is more suitableVisual observation (urban skies): Good, for telescopes up to 5" (125mm) apertureTechnical dataTypical transmission of 94% at 486nm (H-beta)Typical transmission of 95% at 496nm (OIII)Typical transmission of 95% at 501nm (OIII)Typical transmission of 94% at 656nm (H-alpha)Transmission range: 465nm to 530nm and above 645nm Full-Width-Half Maximum (FWHM): 45nm Glass thickness: 1mm (except Astronomik OWB Type 3 and XT filters)Finely polished optical glass, free of any striae, residual stresses, and bubblesExtremely scratch-resistant and durable coatingCompletely resistant against high humidity and aging effectsAstronomik MFR coating (Astronomik Deep-Sky RGB, UV-IR Block L-1, L-2, L-3, and Narrowband-Emissionline filters)Parfocal with other Astronomik filtersDiffraction-limitedOptimized spectral windowsDelivered in a high-quality, long-lasting filter boxDue to the high-precision machining of the carrier substrate, all Astronomik filters are parfocal with wedge errors far below all common tolerances. Astronomik filters are diffraction-limited, ensuring that the optical performance (resolution and contrast) of your telescope is not compromised. Issues concerning focal distances and the exact alignment of images from each color channel are therefore effectively eliminated. All Astronomik filters are ideal for modern cameras, including both CMOS- and CCD-based models, ensuring you capture the best possible images with your equipment. Sharpness, contrast, and the absence of any reflections and halos are guaranteed. Even with bright stars in the field of view, nebulae and galaxies will be captured with the finest structures. The Astronomik MFR coating is designed for optimal performance across a wide range of focal ratios of the optics used.Every Astronomik filter undergoes a rigorous quality control process before delivery. Additionally, each Astronomik Narrowband-Emissionline filter is measured using a high-end PerkinElmer Spectrophotometer to ensure it meets the specifications published on our website. On the back of each Narrowband-Emissionline filter box, you will find a label detailing the precise spectral data for that specific filter, including the maximum transmission and the recommended range of focal ratios.