A small tube whose only job is to watch one star · review
Alstar's 50 mm guide scope: 200 mm focal length, fully multi-coated, a double helical focuser with brass compression ring and 40 mm of focus range, a male T-thread, rings and a Synta-style plate.
Alstar publishes the aperture, the focal length and a limit: 50 mm, 200 mm, for main telescopes up to 1500 mm. The last figure is generous; for mains beyond about 1000 mm a longer guide scope guides more precisely.
A double helical focuser with a brass compression ring and two thumbscrews, 40 mm of total focus range including 10 mm of micro-focus, and a scaled, lockable drawtube. The camera does not rotate as it focuses.
Pipe clamps, a Synta-style dovetail plate and an adjustable balance weight. A male metric T-thread on the focuser collar for guide cameras; a 1.25-inch eyepiece turns it into a finder.
Amazon’s item data gives 590 g (1.3 lb), against 907 g for Alstar’s 60 mm. On a small mount or a star tracker, that difference matters.
On November 7, 2026, Amazon.com listed it at about $78 from a third-party seller.
Figures as Keepa reported them on the day this page was last updated. Stock and pricing shift without warning.
Prices quoted in this text were read on November 7, 2026. The live price is at the top of the page.
Same aisle, closest price — what the same spend else shows.
| Aperture | 50 mm (1.97 in), fully multi-coated |
|---|---|
| Focal length | 200 mm (7.87 in) · stated for main telescopes up to 1500 mm |
| Mounting method | Pipe clamps and a Synta-style dovetail plate · adjustable dovetail weight |
| Flexure resistance | Zero flexure claimed · secure locking mechanism on the drawtube |
| Focuser type | Double helical focuser with brass compression ring and two thumbscrews · 40 mm total focus range including 10 mm of micro-focus · scaled drawtube |
| Back focus | Not published by the maker · male metric T-thread on the focuser collar · accepts a 1.25 in eyepiece |
| Weight | Not published in the listing text · Amazon's item data gives 590 g (1.3 lb) |
| Amazon reference | B074DQWJYW |
| EAN | 6970019299839 |
For mains up to about 1000 mm, yes, with a typical small-pixel guide camera. Alstar states up to 1500 mm; at that length a longer guide scope or an off-axis guider is the safer choice.
Weight. On a small mount every ounce counts, and 50 mm still finds plenty of guide stars with a modern camera.
A male metric T-thread on the focuser collar, for guide cameras with a female T-thread; or the camera's 1.25-inch nosepiece in the compression ring.
7.2/ 10
A well-detailed small guide scope that publishes the main-telescope limit most of its rivals leave unsaid.
This model is listed on Amazon.com, at ≈ $78 at the last reading. Listed is not the same as in stock: availability changes daily, and the buy box shows the live price.
Details checked on November 7, 2026.
Guiding a main telescope of moderate focal length, and doubling as a wide finder
Specifications: the manufacturer sheet for telescopes and observing optics and the matching Amazon product page. Prices and availability: Keepa. Every figure on this page names its source.
60 mm (2.36 in) FMC · 240 mm focal length · helical focuser with brass ring · 80 mm rings for 53 to 79 mm tubes · Teflon inlays
Astromania's 60 mm FMC guide scope: 240 mm focal length, a helical focuser with brass compression ring and 45 mm of range, male T-threads, and two rings of 80 mm bore with Teflon inlays on a Synta-style plate.
Best for: A guide scope whose rings have to clamp a 53 to 79 mm tube without marking it
≈ $98
60 mm (2.36 in) · 240 mm (9.45 in) focal length · helical focuser with brass compression ring · 48 mm focus range · Synta dovetail
Alstar's 60 mm guide scope: 240 mm focal length, fully multi-coated, a helical focuser with brass compression ring and 48 mm of total focus range, a male T-thread for guide cameras, rings and a Synta-style plate.
Best for: A guiding setup for a main telescope up to 1500 mm, also used as a finder
≈ $96
70 mm (2.76 in) · 400 mm (15.7 in) focal length · helical focuser with brass ring · 90 mm focus range · takes 1.25 in eyepieces
Astromania's GS70 deluxe guide scope: 70 mm aperture and 400 mm focal length, a double helical focuser with brass compression ring and 90 mm of range, pipe clamps, a Synta-style plate and a balance weight.
Best for: Guiding a longer main telescope, where a short guide scope would not resolve the correction
≈ $156
