Not recommended for focusing of deep-sky astrophotos, but can be used for framing objects. Microprism and rangefinder black out at high focal ratios usually encountered in telescopes. Rest of screen not that bright. Focusing on fresnel portion of screen more difficult than on plain groundglass screens. Not that great for astrophotography, but usable.
Rangefinder blacks out at high focal ratios usually encountered in telescopes.
The rest of screen is not that bright. Focusing on fresnel portion of screen more difficult than on plain groundglass screens. Not that great for astrophotography, but usable. 12mm reference circle and horizontal and vertical lines. Used when preparing slides for TV broadcasts.