Finder Scopes and Guide Scopes for Telescopes
A finder helps you point a telescope accurately at a celestial object. Options include simple red dot finders, magnifying optical finder scopes with straight-through or angled viewing, and compact guide scopes for astrophotography. The right choice depends on whether you want quick aiming, a brighter view of faint stars, or a guide camera to help monitor tracking.
Compare the magnification and aperture of optical finders, image orientation, mounting style and finder shoe. Also check that the accessory fits your telescope and can be aligned securely.
Which type of finder suits your observing?
Red dot and reflex finders place an illuminated dot or target circles against the open sky. They do not magnify: you look at the sky with both eyes open and move the dot onto your target. This makes them intuitive for quick aiming at bright stars, the Moon and planets. A display that is too bright can interfere with dark adaptation, so adjustable brightness is useful. Before observing, align the finder parallel to the main telescope using a distant daytime target or another easy reference.
Optical finder scopes magnify a wider area of sky and reveal more stars than the naked eye. For example, 6x30 means 6x magnification with a 30 mm objective; 9x50 means 9x with a 50 mm objective. A larger aperture gathers more light, while higher magnification can narrow the field and make targets harder to acquire. A reticle helps with accurate centring. Check the image orientation stated for each product: depending on its optical design, a straight-through finder may show a rotated or reversed image.
Right-angle finders turn the viewing direction sideways. A 90-degree Amici prism can provide an upright, correctly oriented image, making orientation easier and reducing neck strain when observing near the zenith. Check each model for its actual image orientation and compatibility with eyepieces or focusers.
Guide scopes are mainly used to monitor tracking during astrophotography. Together with a suitable guide camera and software, they measure guide-star drift and help the mount make corrections. Aperture, focal length, focusing, camera connection, mounting and rigidity should suit the imaging telescope and mount. A guide scope is not automatically a visual finder, and a camera or mounting hardware may not be included; check the individual product details.
Mounting and alignment
Many finders fit into a shoe on the telescope tube. Dovetail shapes and dimensions are not identical across all manufacturers, so compare the finder foot, shoe and telescope mounting surface before ordering. Replacement shoes with different support surfaces and slotted holes are also available. On curved tubes or tube rings, the base must sit securely; check screw spacing and use suitable screws. A firm fit prevents the finder from shifting as the telescope moves.
First point the finder at a distant, easy-to-identify target and centre it in the main telescope. Then adjust the finder screws until the same target is centred in the finder. For astronomy, refine the alignment on a bright star. The initial alignment is complete when the target remains in the main eyepiece and finder after moving the telescope.
Quick selection guide
- Fast aiming with both eyes open: choose a red dot or reflex finder; check brightness adjustment and base compatibility.
- See more stars in the finder: choose an optical finder scope; compare aperture, magnification, field of view, reticle and image orientation.
- Comfortable viewing or an upright terrestrial image: choose an angled finder with the appropriate prism and confirmed image orientation.
- Astrophotography guiding: match the guide scope and camera to focal length, connection, focus travel and stable mounting.
- Replacement or upgrade: select a finder shoe and bracket by mounting surface, hole spacing and finder-foot shape.
For imaging setups, browse astrophotography accessories and more telescope accessories.