Astromania 1.25" 4mm 58-Degree Planetary Eyepiece - Bundle with - 1.25" Narrowband H-Beta Filter

One of our High Transmission (HT) precision range of filters, this 1.25" H-Beta Filter is sure to impress on performance, quality and price. It comes with its own individual data sheet of performance - guaranteed! It is an extremely useful filter for observing the very feint nebulae. It has a very limited transmission range of 484 - 490nm (70%) and 478 - 483 & 492- 497nm (60+%). The very sharp cut offs only allow the hydrogen beta light that these feint objects emit to pass through. By cutting off almost all of the visual spectrum the filter effectively blackens the sky to make these objects show through. This filter is best used on large aperture telescopes (8" +) under very good seeing conditions and is an essential item for those astronomers who enjoy tracking down the most elusive of deep space objects. This is a filter for visual observational use.

• Filter with metal mount 1.25 inch filter threads on both sides
• The combination of three lens elements means Astromania 2X short Barlow provides particularly clear and sharp images
• Have extremely high transmissions while completely rejecting light pollution and important blocking of longer wavelengths; substrate is fine-optically polished plane parallel to deliver a smooth and accurate 0.25 wavefront over entire surface
• Designed primarily for planetary observation "Moon; Jupiter; Mars and Saturn and more" but great for deep sky objects too; comfortable eye relief averaging 16mm across the series; threaded for standard 1.25- inch astronomy filters
• 58 degree field of view: 2.5-25mm focal length; equipped with rotated adjustment eyepiece barrel and eye convertible rubber ring for eye; give maximum detail and definition for high transmittance and contrast ratio with least lateral chromatic aberration