A small tube whose only job is to watch one star · review
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.
The GS70 is the largest guide scope on this shelf, and the longest: 70 mm of aperture and 400 mm of focal length. A longer guide scope resolves smaller star movements, which matters when the main telescope is 1000 mm or more.
A double helical focuser with a brass compression ring and two thumbscrews gives 10 mm of fine focus, and a fixable, scaled drawtube makes up the rest of a 90 mm range. That is enough for almost any guide camera without extension tubes.
Pipe clamps, a Synta-style plate and an adjustable dovetail weight. A lock thumbscrew and two hex screws hold the extension tube.
Amazon’s item data gives 1.13 kg (2.5 lb), the most on this shelf. It belongs on a mount with payload to spare.
On November 7, 2026, Amazon.com listed it at about $156 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 | 70 mm (2.76 in), fully multi-coated |
|---|---|
| Focal length | 400 mm (15.7 in), stated |
| Mounting method | Matching pipe clamps and a Synta-style mounting plate · adjustable dovetail weight |
| Flexure resistance | Not published as a claim · lock thumbscrew and two hex screws hold the extension tube |
| Focuser type | Double helical (worm) focuser with brass compression ring and two thumbscrews · 90 mm range: 10 mm helical plus a fixable scaled drawtube |
| Back focus | Not published by the maker · takes 1.25 in eyepieces |
| Weight | Not published in the listing text · Amazon's item data gives 1.13 kg (2.5 lb) |
| Amazon reference | B0799FK1RX |
| EAN | 6971336223347 |
For main telescopes of 1000 mm and more. A longer guide scope sees smaller star movements, so its corrections match what the main camera records.
On a star tracker or a light mount, yes. Amazon's item data gives 2.5 lb before rings and camera; check your mount's payload.
Yes: it takes a 1.25 in eyepiece. At 400 mm, a 25 mm eyepiece gives 16x.
8.4/ 10
The largest and longest guide scope on this shelf at 70 mm and 400 mm, and the heaviest one to carry.
This model is listed on Amazon.com, at ≈ $156 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 longer main telescope, where a short guide scope would not resolve the correction
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.
50 mm (1.97 in) · 200 mm (7.87 in) focal length · helical focuser with brass compression ring · 40 mm focus range
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.
Best for: Guiding a main telescope of moderate focal length, and doubling as a wide finder
≈ $78
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
