A finder is a must-have for pretty much any telescope. Even if your telescope is a GoTo-mounted instrument, you’ll need a finder of some sort to align it on stars, or to aid in pointing if the computer system is inaccurate or unavailable. Most telescopes come with some sort of finder, but it may not necessarily be a good one or what fits your needs.
Optical Design Options – Advantages & Disadvantages
There are essentially three types of telescope finder scopes available to amateurs, besides entirely mechanical options like an iron sight, which are seldom used.
Red-dot or reflex sight finders use an LED and a lens to project a red-colored reticle of some sort onto a plastic viewing window, which you look through to see the reticle superimposed on the sky. These finders require a battery but are extremely intuitive and comfortable to use. High-quality reflex sights have a “bullseye” reticle with degree circles, which can be used as an approximate reference measurement to compare to star charts as you find your way around the sky. Red dot and reflex sight finders are cheap, dew is of little concern as you can simply wipe off the viewing window with your sleeve if it fogs up, and they weigh very little so they won’t affect the balance of your telescope as much. However, you are limited to whatever stars you can see with your naked eye, which may be a problem in light-polluted settings where large areas of sky may be devoid of anything to use as a reference, and these finders of course require batteries.
Magnifying finders, also referred to as finder scopes (though some red dots are confusingly also given this label), are essentially a small refracting telescope (usually an f/4 achromat) with a crosshair or reticle eyepiece. They come in two types: straight-through and right-angle. Almost all straight-through finders have an upside-down image, while right-angle finders almost always have an Amici prism to correct the image left-right to match the orientation of what you see in the sky or on a star chart. The straight-through finders are cheaper, and the upside-down view matches what you see through a Newtonian reflector – but using one when aimed high in the sky is uncomfortable. Right-angle finders can be difficult to get coarsely aimed in the right direction but are comfortable to use while also matching the orientation of your star charts and astronomy apps.
Magnifying finders generally need to have a true field of view of 4 degrees (8x the diameter of the full Moon or the Sun in the sky) or greater, and a magnification below 12x, to be useful on their own, much like a pair of binoculars. Higher magnification and a narrower field may be desirable if you need pinpoint accuracy or have a very large aperture finder, but they generally inhibit coarse aiming without the addition of a lower-power finder or reflex sight to help you get started. A good-quality 50mm finder has a true field of at least 5.5 degrees, or about 11 times the angular diameter of the full Moon; larger and smaller finders will typically have a narrower or wider field, respectively.
Generally, most people find red dot and reflex sights to be the most intuitive, and they work well on their own but can also be great when used in conjunction with a right-angle correct-image finder. A straight-through finder is typically used by itself, while right-angle correct-image finders can be difficult to use without any other kind of finder or other aid in aiming on account of the difficulty in getting coarsely aimed in the right direction with one.
Many finders attach to your telescope with a standard shoe, which allows them to be easily interchanged with another finder, usually of the Vixen/Synta style. The other most common bracket system is the Explore Scientific/Meade/Bresser system, which is starting to be phased out. Other attachment systems include directly mounting to the telescope with screws or adhesive tape and Picatinny rail attachments.
Best Red Dot & Reflex Sights
Not all red dot and reflex sights are created equal. Some can have tinted windows, reticles and dots that shift when your head moves (parallax error), difficult-to-use adjustments, or simply poor quality. A reflex sight is easily used on its own, while a red dot may not suffice unless you are only using it on the brightest targets or as a supplement to another finder or GoTo system. Here are our top five picks for both types.
#1 – Telrad – Best
The original reflex sight, the Telrad, hasn’t changed much since the 1970s, when it was invented, and still uses the original injection mold from 1982. The Telrad’s big viewing window makes it easy to look through, while its reticle of 0.5, 2- and 4-degree circles is easily adjusted in brightness and doesn’t shift with your head. The Telrad attaches to your telescope with its own base, which can be taped, glued, or screwed to your telescope (or attached to a finder shoe with a suitable adapter), and numerous accessories, including pulse/blink units, dew heaters, dew shield attachments, and a riser to increase its distance from the tube, are available. You can also convert a Telrad to run off DC power, eliminating the need for its pair of AA batteries altogether.
The biggest downside of the Telrad is its size; it simply won’t fit on smaller telescopes and may be difficult to fit if your scope is already equipped with a RACI finder. The large plastic window is also prone to dew, but simply wiping it or adding a dew shield/heater is hardly an inconvenience. The good news is that the Telrad is mostly hollow, and it doesn’t actually weigh much in spite of its size, though it will still affect balance more than a smaller reflex sight or red dot finder.
Most large amateur telescopes use a Telrad for pointing, and it may easily be the only finder you need.
#2 – Rigel QuikFinder – Most Compact
Essentially a smaller version of the Telrad, the Rigel Quikfinder features a 0.5-degree and 2-degree “bullseye” reticle and a built-in pulse unit and dew shield by default, running on a CR2032 battery. The Rigel Quikfinder is ideal for scopes where the Telrad won’t fit, though it does have some parallax error and the lack of a 4-degree circle means it isn’t quite as easy to use. You can install an AA battery pack if you wish, or run the Quikfinder off DC power if that suits you similarly to the Telrad.
#3 – Explore Scientific ReflexSight
Explore Scientific’s rather unimaginatively named ReflexSight is a carbon copy of the Telrad in many ways, with the same basic form factor, set of 0.5-degree, 2-degree, and 4-degree circles, and lack of parallax error. It attaches to telescopes with a standard Vixen/Synta style shoe or a ¼ 20 screw, and runs off smaller AAA batteries. A flip-up cover for the window to protect it from dew, dust, and damage is also built-in. However, the ReflexSight is quite a bit more expensive than the Telrad, and the actual in-use performance is basically the same.
#4 – SVBONY Red Dot – Cheapest
The SVBONY red dot finder is the same as the “StarPointer” and “EZ Finder” attached to many other telescopes and can be purchased with either a Vixen/Synta-style shoe or a 2-hole bracket for mounting to cheap telescopes that lack a finder shoe. It runs on a CR2032 battery and projects a simple dot. There isn’t really much else to it; this finder does the job.
Essentially a modified red dot sight with a fatter window and a circular reticle, the Celestron StarPointer Pro is favored by some but has few advantages over true reflex sights or a standard red dot finder while also costing quite a bit. It attaches to a standard Vixen/Synta-style shoe and runs on a CR2032 battery just like a normal red dot.
Best Straight Through Finder Scopes
#1 – Takahashi 7×50 Finderscope – Best Quality
Takahashi’s 7×50 finder scope is so well-made that it is actually designed to be used as a carry handle on their Mewlon Dall-Kirkham telescopes. Seriously. This finder is extremely sharp, the 7x magnification produces a brighter exit pupil that’s easier to center your head on than higher magnification finders, and the 6.3-degree true field is fairly wide (though the 44-degree apparent field is hardly immersive, it’s impossible to get lost in the view). Focusing is accomplished by twisting the eyepiece. However, you do need to buy a bracket separately, and the price is quite high.
#2 – Explore Scientific 8×50 Straight-Through Correct Image Finder Scope – Most Features
Explore Scientific’s high-end 8×50 straight-through finder actually has a Roof prism to put the image upright, like binoculars or a RACI finder scope. This finder also features an illuminated reticle, which is AAA battery-powered and will light up multiple degree markings etched in its crosshairs. The focus is adjusted by twisting the eyepiece end, and the field of view is 6 degrees, translating to an apparent field of 48 degrees at the eyepiece. This finder’s ring/bracket assembly attaches to a shoe/base with the ES/Bresser/Meade system, but adapters or hybrid bases are fairly easy to obtain.
#3 – Astromania 70mm Compact Deluxe Finder & Guidescope Kit – Best Performance
Also available in 60mm and 50mm formats, Astromania’s finder/guide scope will require you to obtain a crosshair eyepiece separately, but it has a nice non-rotating helical focusing system, a sturdy bracket compatible with Vixen/Synta bases, and a 70mm aperture that will allow you to gather a lot of light and see more stars and deep-sky objects in the view. It may not reach focus with a diagonal and, as such, is probably best used configured as a straight-through finder. With a typical 25mm Plossl eyepiece, the magnification will be 16x and the field will be 3.25 degrees across, making it best for use on larger telescopes (smaller scopes’ balance will be upset by such a big finder anyway, and it may not even fit).
#4 – Orion 9×50 Achromat Finderscope – Best Economy
Usually the same finder is supplied on many telescopes that use a 9×50 unit; the Orion 9×50 Achromat Finderscope attaches to any Synta/Vixen-style finderscope shoe. This 9×50 has a fairly narrow true field of only 5.5 degrees and a rather uncomfortable eyepiece with a small diameter, no eye guard, and short eye relief. Focus is also only adjusted by turning a ring at the front, which can be annoying to do without affecting alignment with a telescope. However, if you’re looking for an affordable 9×50 unit, this finder is tack sharp and does the trick, though it’s not quite as luxurious as a more expensive unit.
#5 – SVBONY SV182 6×30 Finderscope – Cheapest
As with the Orion 9×50, the SVBONY SV182 6×30 unit is a pretty generic unit supplied with many beginner telescopes under many brand names, with a variety of paint jobs, attaching to a standard Synta/Vixen-style finder shoe at the bottom of its bracket. It has a fixed eyepiece with no lifeguard, and the lens is adjusted to focus the telescope by rotating its retaining ring at the front. The low amount of light collected by a 30mm finder means you won’t see much more than with your eyes alone, but the additional magnification and crosshairs make this finder more accurate than a cheap red dot. It also remains fairly lightweight and affordable, while also offering a huge 7-degree true field.
Best RACI Finder Scopes
#1 – Baader Vario 10×60 Finder Scope – Most Features
The 60mm aperture sported by the Baader Vario gives it plenty of light-collecting ability, and its optics are sharp enough that it can be used as a general-purpose telescope on its own thanks to the 1.25” rear port and separate Vixen-style dovetail (also compatible with photo tripods). While supplied with a 45-degree erecting prism for some reason, it’s easy enough to convert the Baader to use a standard 90-degree Amici diagonal, and it has a T2-threaded nonrotating helical focuser at the back. The provided 25mm Polaris T2 reticle eyepiece produces 10x magnification and a 4-degree true field that is rather narrow but extremely sharp, and the illuminated reticle has double crosshairs to avoid obscuring your target and is adjustable for brightness. The reticle is also sealed so dust cannot get on the focal plane of the eyepiece and ruin the view. Attachment with various different finder base designs is also possible.
Similar in design to finders sold by other brands like Stellarvue and Antares at a lower price tag, Apertura’s 10×50 RACI finder features an illuminated-reticle 20mm crosshair eyepiece, allowing for a 5-degree true field of view but easily swapped out for a wider-field eyepiece permitting up to an 8.5-degree true field if you wish. The eye relief is plenty, and the view with the stock eyepiece is quite sharp. Focus is adjusted with a helical unit attached to the Amici prism diagonal. The Apertura 10×50’s bracket attaches to your telescope via a Vixen/Synta style shoe, and an extra one is conveniently provided with this finder, so you don’t have to go shopping for a base or remove your current finder.
Explore Scientific’s 8×50 RACI finder features a huge 7-degree true field and a built-in nonrotating helical focuser, along with, of course, an illuminated reticle. However, the provided reticle is not a standard crosshair but rather a polar axis reticle, showing labels of what the sky around Polaris looks like—a convenience if you are using it to polar align an equatorially-mounted telescope but otherwise a rather unusual and distracting addition. Nonetheless, this is an extremely well-made finder, though it only attaches to ES/Bresser/Meade finder base plates by default.
#4 – Apertura 8×50 Right Angle Finderscope – Best Economy
The same GSO-made unit supplied with Apertura’s Dobsonians and many other telescopes, the Apertura 8×50 RACI finderscope is a fairly basic, inexpensive finder: a fixed, tiny eyepiece, a difficult-to-adjust “focusing mechanism” via adjusting the objective lens retaining ring, and a fairly narrow true field at only 5.6 degrees – although still plenty sharp. As usual, it attaches to your telescope with a Vixen/Synta-style shoe. For many people, the Apertura 8×50 may be just fine, and there is little need to spend more on a fancier finder, but many users may find using one for long periods uncomfortable without an eye guard or an easy method for adjusting focus.
#5 – SVBONY SV182 6×30 RACI Finderscope – Cheapest
Essentially a shrunken version of the Apertura 8×50, SVBONY’s 6×30 RACI finder (sold under many other brand names) is limited by its aperture and of course sports a fairly basic mechanical design, but it’s a lot more comfortable to use for extended periods than a straight through or red dot finder, and the 7-degree true field means that it is fairly easy to use even without the aid of a red dot or reflex sight. However, the lack of light gathering ability may make it less effective to use under more light-polluted conditions compared to an 8×50 unit.