Broad Band Nebular Filter 911B (Rear Cell Thread)

For an increase in visual and photographic detail in deep-space emission and reflection nebulae.
Meade Series 4000 Nebular Filters incorporate the very latest in interference coatings technology. Each filter includes more than 40 coating layers to reject, with precision unwanted light from urban light pollution while passing critical nebular emissions with minimal reduction.
The Meade Broadband Nebular Filter strongly rejects the light of sodium- and mercury-vapor lights as well as natural airglow and auroral emissions. Conversely, the strong nebular emission spectral lines, transmitting in the visually sensitive regions primarily at 486nm (Hydrogen Beta, or Hß) and 496 to 501nm (Oxygen-III, or OIII), are passed through the filter with high transmission percentages. The effect of the filter is that nebular light reaching the eye is observed visually in dramatically increased detail, while the effects of unwanted city lights are greatly reduced. The Meade Broadband Filter also passes photographically-important Hydrogen Alpha nebular light at 656nm largely unattenuated, making the filter a valuable aid in the photography of deep-space emission nebulae as well. The contrast between galaxies and the night-sky backdrop is also typically enhanced by the filter, but because galaxies emit light in a much broader range of wavelengths than nebulae, the effect is generally not as dramatic in these cases.
This filter is designed to fit the rear cell of most Scmidt Cassegrain telescopes.