Orion 5581 1.25-Inch Oxygen-III Nebula Eyepiece Filter<div style="text-align: left;"><strong>[Product Information]</strong><ul><li id="replacementPartsFitmentBullet" class="aok-hidden" data-doesntfitmessage="We're not sure this item fits your " data-fitsmessage="This fits your "><span class="a-list-item"><span id="replacementPartsFitmentBulletInner"><a href="#" class="a-link-normal hsx-rpp-fitment-focus">Enter your model number</a>to make sure this fits.</span></span></li><li><span class="a-list-item"> Orion's Oxygen-III (O-III) eyepiece filter reveals wondrous details when viewing cloudy nebulas </span></li><li><span class="a-list-item"> Filter transmits close to 90% of the light corresponding to 2 oxygen-III spectral lines at 496nm and 501nm for enhanced nebula detail in visual views </span></li><li><span class="a-list-item"> Completely blocks virtually all other visible wavelengths of light so views of nebulas are optimized </span></li><li><span class="a-list-item"> Eyepiece filter features high quality optical glass in a double-threaded， metal filter cell </span></li><li><span class="a-list-item"> Recommended for use with telescopes of 8" aperture or greater for best results and for visual use only </span></li></ul></div><img src="http://ecx.images-amazon.com/images/I/514BA0MR1GL.jpg" noproxy>