H-Alpha filter 1.25" 12nm from Explore Scientific is an indispensable tool for astrophotographers wishing to capture emission nebulae, even under a sky polluted by artificial light. This filter blocks almost all other colors, allowing only the emission line of red hydrogen to pass through. It effectively eliminates the disturbing light from mercury and sodium vapor lamps, revealing details invisible to the naked eye. With a bandwidth of 12nm, this filter enhances the contrast and sharpness of deep sky objects, allowing for the photographing of nebulae that appear invisible without the filter. Ideal for astrophotographers in urban environments, it ensures results of surprising quality despite light pollution. Each filter comes with an individual test certificate to guarantee its high quality.