Meade Series 4000 Nebular Filters incorporate the very latest in interference coatings technology. Each filter includes more than 40 coating layers to precisely reject unwanted light from urban light pollution while allowing critical nebular emissions to pass through with minimal reduction.
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, making the filter a valuable aid in the photography of deep-space emission nebulae. The contrast between galaxies and the night-sky backdrop is 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.
The #911B threads onto the rear cells of Meade LX-series mirror-lens telescopes and as well as to the rear cells of other Schmidt-Cassegrain telescopes. In this manner the telescopes are converted into a basic nebular mode, for visual observing or for photography with the T-Adapter or Off-Axis Guider. The clear aperture is 36mm. The advantage of this rear cell filter is that it affords the user the convenience of exchanging eyepieces quickly, whether 2.00" or 1.25". It also works with deep space photography accessories and will seal the rear cell from incoming dust.