Whether youre looking to build a telescope system from scratch or wish to upgrade your kit star diagonal the altair astro 2 inch quartz dielectric diagonal offers 99 reflectivity due to its multi layer dielectric coatings and extreme durability thanks to its cnc machined aluminium casing it has a non marring brass compression ring to prevent damage to your eyepieces and comes supplied with two protective dust caps in foam lined presentation box the fused quartz medium expands and contra