Explore Scientific H-Beta Filter 1.25" Narrowband Filter for H-Beta sources Useful where you do not have a dark-sky site Observe deep-sky nebulae from brighter areas Increase contrast of deep-sky objects Range: 478 nm to 496 nm; peaks at 489 nm 94.5% Transmission Fits 1.25" Eyepieces This is a stray light reduction filter which fits into your 1.25" eyepieces that have internal (female) filter threads. The Explore Scientific Narrowband H-Beta Filter 1.25" is designed for observing deep sky objects which glow in H-Beta light, and it is tuned specifically to pass the H-beta wavelength band of light. Hydrogen is the most abundant element in the Universe and many nebulae glow in the H-beta light. The H-Beta Narrowband Filter 1.25" from Explore Scientific does a good job of increasing contrast, providing a darker sky background. It does this by filtering out all the other wavelengths of light, while allowing the light from H-Beta nebulae or other sources to pass through so you can see them better. It has a total transmission specification of 94.5%.
