The Magnification Myth: Why 525x Means Nothing

Magnification is telescope focal length divided by eyepiece focal length, so this kit is the variable in that equation. On a 650mm f/5 telescope the 32mm gives 20x, the 13mm gives 50x and the 6mm gives 108x. On a 1200mm Dobsonian the same three give 38x, 92x and 200x.

The 2x Barlow halves every eyepiece's effective focal length, which is where the ten-eyepieces-in-one claim comes from. It is true arithmetic, but a Barlow on a 6mm eyepiece produces 3mm, and on most beginner telescopes 3mm is beyond the useful magnification the aperture supports.

The useful lesson is that the two eyepieces in the telescope's box are usually the two least considered items in it. A 32mm Plossl in a fast Dobsonian gives a genuinely wide, bright field that no bundled eyepiece will match.

A moon filter is not optional at full Moon in anything over about 100mm. The Moon at 130mm is uncomfortably bright, and that is not a figure of speech.

This is the aperture-per-dollar champion of the beginner shelf and it is not close. You get the same 130mm parabolic mirror found in telescopes at twice the price, and you get it without paying for a tripod, a slow-motion assembly or a hand controller.

Two times 130mm is 260x of useful magnification. Dawes' limit at 130mm works out to 116 divided by 130, which is 0.89 arcseconds. The Cassini division in Saturn's rings spans roughly 0.7 arcseconds at its widest, so this telescope sits right at the edge of showing it on a still night and will show the rings themselves easily.

The catch is the word tabletop. It needs a surface at roughly chest height when you are seated. A garden table works, a plastic patio chair does not, and buying one without thinking about where it will stand is the single most common regret with this design.

The tube collapses, which is what makes it live in a cupboard rather than a garage. That matters more than it sounds: the telescope you can carry outside in one trip is the telescope you use.

70mm is the floor. Below it a telescope struggles to beat a decent pair of binoculars, and that is a real comparison rather than a rhetorical one. Two times 70mm gives 140x of useful magnification; Celestron publishes 165x.

The defining number is the focal length. Celestron publishes 900mm, which at 70mm is f/13, an unusually slow ratio for a beginner refractor. A slow achromat brings the colors closer to a common focus, so the violet fringe on the Moon and on Jupiter is smaller than on a faster tube of the same aperture.

The same slow ratio narrows the field. At 45x with the supplied 20mm eyepiece, large star clusters that fit comfortably in a short refractor will not fit here, and finding things takes a steadier hand on the red dot finder.

It is also a large, heavy package for 70mm of aperture: a 685mm tube and a published 10.8 lb kit. That buys a steadier steel tripod than the lightest travel telescopes carry, and it costs portability.