Details
Description
A very good quality rear cell filter from Meade in Mint condition
Details from the web below:
Meade Series 4000 #911B Broadband 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 #911B 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 H) 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.