Nebula filter for increasing contrast; also suitable for use with smaller telescopes
Many objects only first become visible at all when using an UHC filter; but also; highlights such as the Orion; Lagoon or Swan nebulae; show a whole new side to them
Can be used at both light-polluted and dark sky sites; blocks the light from mercury and sodium-vapour lamps
For precise focusing: flip mirror makes easy to find exact focus point and also correct position for astrophotography; this small black box has a moveable flip mirror which shunts light path 90 degree upwards; alternatively lets it pass through unhindered
Always sharp: If tilt mirror to 45 degree position; object will appear in eyepiece and precisely focus it as usual; helical focuser on flip mirror lets to make eyepiece and camera exactly parfocal; this means elements will be in focus at the same time