Scope Views Home



Follow @scope_views


Kowa TS-501 Review

This is the first (and may remain the only) review of a spotting scope on ScopeViews! The reason is that prismatic scopes, great for erect-image nature viewing, are a bit limited for astronomy because the prisms typically distort star images and prevent high magnifications. To use a spotting scope for astronomy at all requires the highest optical and mechanical quality. Kowa interested me because they have a reputation for delivering that (Japanese made) quality at a much lower price than the main premium brands. Their entry level model, the TS-501, has potential as a travel scope because it is tiny, feather-weight and rugged.

Design and Build

The TS-501, effectively including diagonal and eyepiece, makes traditional travel scopes look big and bulky. It must weigh under a kilo and fits on your palm.

Simple eyepiece giving a narrow field and modest eye relief.

50mm lens has single coatings (or perhaps very basic multi-coatings).


The TS-501 has a built-in eyepiece giving a magnification of 20x. The eyepiece is not interchangeable on this model. The eyepiece is angled at 60 degrees, but they also made an otherwise-identical straight-through version.

The lens is a 50mm achromat with what appear to be single coatings.


The body is made of some kind of tough plastic – it’s not pretty, but you can tell it would stand up well to outdoor rigours. It is not sealed and purged, but looks as if it would withstand a heavy shower without problems.

Focusing is by an internal mechanism like all spotting scopes: you just twist the yellow knob.

In Use - Daytime

The TS-501 is quite basic, but in terms of quality it’s good: the focuser is smooth and accurate, the lens well-figured and everything perfectly collimated.

The view is good too, but the field of view is narrow and the eye relief too small for use with specs. My guess is that – in line with the rest of the scope – the eyepiece is a fairly simple design.

In Use – The Night Sky

At night, the small aperture and single coatings, plus the light-robbing prisms mean the view is rather dim and that, combined with a narrow field of view, make finding things hard. So if you do use this for astronomy it will be for the Moon and bright planets, not deep sky objects and star-fields. There is a big difference with a dedicated astro-scope here. The  MiniBorg 50 has the same aperture and is actually amazingly good on the brighter DSOs.

The Moon

So if you point the TS-501 at the Moon, what can you see? Quite a lot actually. The image is sharp and crisp; chromatic aberration, whilst present on the limb, is well-controlled. I’ve seen cheap spotting scopes that make a real mess of the Moon, but not this one.

Most of the main features, the Maria and larger craters, are visible. You can see Tycho and its rays, the Sinus Iridium, Copernicus and its central peaks, dark-floored Plato, Mare Criseum and bright Proclus. You could certainly buy an atlas (or a Smartphone app these days) and start to learn your way around Luna’s enthralling alien and rugged topography with the TS-501.


Unfortunately dazzling Venus always causes flare in prismatic systems, obscuring its phase. The Outermost planets are too faint to find easily in any 50mm scope, never mind one with a dim narrow field and no finder. That leaves Mars, Jupiter and Saturn on the TS-501 observing schedule.

Mars is just a red dot at 20x. Saturn reveals a hint of its rings in the form of the ‘jug handles’ familiar from Galileo’s drawings (he was using about 20x too). Jupiter impresses with all four Galilean moons and both main cloud belts – the north and south Equatorial Belts (NEB and SEB). Again, many prismatic systems – both scopes and binos – make a real mess of Jupiter with just a flared blob in place of a planet, but not so the TS-501.

Deep Sky

The only one I was easily able to locate and view was M42, The Great Nebula in Orion. Due to its magnification, the TS-501 showed more of M42’s arching shape than binoculars, but only the bright central region of nebulosity was visible.

The dim optics meant the Pleiades lacked their customary refractor glitter.


The TS-501 delivers on the Kowa promise of quality. There is nothing glamorous about it, but optical quality is high and the focuser smooth and accurate. For astronomy it is limited, though and not just by its small aperture. The single coatings and prism system seem to waste a lot of light, so the TS-501 is really too dim for all but the brightest DSOs (i.e. M42). However the 20x magnification and sharp optics will show a fair bit of detail on the moon and the main belts on Jupiter. If you want a tiny travel scope, though, a Mini Borg 50 will show you a lot more and is the better bet, unless you really need the semi-sealed and rugged Kowa.

Not recommended to buy specifically for astronomy, but quite usable for quick looks at the moon and Jupiter (unlike most cheap spotting scopes!). Or shove it in your bag for a peek at that upside down Moon in Aussie.