Optolong Hydrogen Beta Visual Filter 25nm

RM 58.50

Optolong Hydrogen Beta 25nm Visual

Optolong Narrowband H-beta filter is designed for nebula observation allowing 25nm bandwidth of light centered on a wavelength of 490nm throughout, halfway between H-beta emission line and OIII. It also reduces the transmission of certain wavelengths of light, specifically those produced by artificial light including mercury vapor, and both high and low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow). H-beta emits 486.1nm and it is a blue colored filter. Some images of planetary nebulae and supernova remnants are taken with H-alpha, H-beta and OIII filters. They show great structural details, but have natural colors, looking like an RGB image

Main Use and Performance

Suitable for visual observation on most emission nebulae, planetary nebulae and supernova remnants. Suitable for viewing on bright nebulae like M42 Orion Nebula in heavy light pollution. Use with a large aperture telescope under clear and dark viewing conditions with good seeing. Due to the fact that this filter will let through a larger amount of light around the OIII emission line, its main purpose is visual observations, however it can also be used with a small telescope for imaging deep sky objects.

Light pollution filters do not eliminate the effects of light pollution or increase the object’s brightness. In many cases, they increase the contrast between nebula and night sky, not brightening the nebula.

Technical Data

Schott substrate material
Glass thickness 2.0 mm (1.25”/2”/36mm)
Surface Quality: 60/40 (Refer to MIL-O-13830)
Fine-optically polished to ensure accurate 1/4 wavefront and < 30 seconds parallelism over both surfaces
90% transmission at major H-beta line 486.1nm, Partial transmission (appr 65-70%) of OIII line at 495.9nm.
Precision off-band blocking, specifically the major emission lines of artificial light pollution (i.e. Na 589nm, Hg 435nm and 578nm).

Filter Cell

Ultra-thin filter cell minimise vignetting by maximising possible clear aperture (clear aperture is 26mm for 1.25” size and 45mm for 2” size)
Aerometal Material
Precise CNC Machining
Sand Blasting Process
Black Anodized Finish
Extinction Treatment to Prevent Reflection
Laser Engraving No Fading

Available Sizes

Standard 1.25” & 2”
Round 36mm Unmounted

Packaging

Plastic PP Case
Imported High Pressure EVA Case Lining
Silver Cardboard Box
High Density Sponge Carton Lining

Optical Coating

Multi-layer anti-reflection coating
Non-cementing optical substrate coating
Electron-beam gun evaporation with Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL(central wavelength) no deviation affected by temperature change.
Planetary rotation system offers precision and homogeneity of coatings ensuring high value on transmission of pass-band and Optical density of off-band. (Please note, "planetary rotation system" is a type of optical coating process and does not refer to the astronomical system describing the motion of the planets in our solar system.)