Finderscope

Specifications

Observing parameters

Overview

A finderscope is a small, low-magnification, wide-field telescope mounted parallel to the main tube. Its only job is to get the target into the main eyepiece. Most time lost at the eyepiece is time spent finding things, not looking at them, so a good finder pays for itself immediately.

Three families: a 6×30 or 9×50 optical finder (magnified, upright image, needs aligning), a red-dot or reflex sight (zero magnification, projects a dot, fast and intuitive), and a "right-angle correct-image" finder. Many observers run both — a red dot for coarse pointing and a magnified finder for star-hopping.

Alignment is the maintenance item. Align the finder on a distant terrestrial object in daylight, then refine on a bright star at dusk. Check it every session.

Where it fits

Practical notes

• Never align a finder on the Sun. Use a distant terrestrial target in daylight.
• A 9×50 finder shows roughly mag 9.5 stars, which matches most printed star atlases — that is why it is the standard.
• Loosen the ring screws evenly in small turns; cranking one side tilts the finder and ruins alignment.
• A reflex sight is the fastest way to aim a GoTo telescope before its alignment stars are set.

Pairs with

• Star Atlas
• Planisphere
• Red Flashlight
• Wide-Field Eyepiece