Orion 5583 1.25-Inch Hydrogen-Beta 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 Hydrogen-Beta eyepiece filter makes it possible to view the elusive Horsehead， California， and Cocoon Nebulas in dark skies </span></li><li><span class="a-list-item"> Selective band-pass filter transmits only the hydrogen-beta light these faint nebulas emit </span></li><li><span class="a-list-item"> Filter allows you to observe targets that are considered trophies of visual astronomy </span></li><li><span class="a-list-item"> Best used with a moderate to large aperture telescope and clear， dark skies </span></li><li><span class="a-list-item"> Metal filter cell threaded to fit 1.25" eyepieces and threaded diagonal barrels </span></li></ul></div><img src="http://ecx.images-amazon.com/images/I/51SS9MY6YAL.jpg" noproxy>