Choosing Your First Telescope

The best first telescope is the one you will actually take outside. It sounds simple, but most telescopes that end up in a cupboard got there because they were too bulky, too fiddly to set up, or showed something disappointing on the very first night.

Start with binoculars

Before buying a telescope, consider a pair of 7×50 or 10×50 binoculars. The first number is the magnification, the second the objective diameter in millimetres. Binoculars give a wide field, are easy to use, and are enough to show lunar craters, the four large moons of Jupiter, the Pleiades and many star clouds along the Milky Way. They also teach you to move between constellations, a skill every telescope demands.

Aperture is the number that matters

Aperture is the diameter of the main mirror or lens. The larger it is, the more light the telescope gathers and the finer the detail it can resolve. A 150 mm telescope collects roughly twice the light of a 100 mm one, because area grows with the square of the diameter.

Be wary of boxes that advertise 500× or 600× magnification. The highest useful magnification of a telescope is about twice its aperture in millimetres, so a 70 mm instrument tops out around 140×. Beyond that the image only gets bigger and dimmer.

The mount matters as much as the tube

A good optical tube on a shaky tripod is a poor experience. At high magnification, the lightest touch sends the target out of view. When comparing two kits at the same price, favour the one with the steadier mount.

A suggestion for beginners

For most beginners we suggest a Dobsonian reflector of 150 to 200 mm aperture. It is a Newtonian reflector on a simple rotating wooden base, with no complex alignment, and it offers the most aperture for the money. Its drawback is bulk, so if you live in a walk-up apartment or travel mostly by motorbike, an 80 to 100 mm refractor on a solid alt-azimuth mount may suit you better.

Computerised go-to telescopes are convenient, but at the same price they usually trade away aperture. On a limited budget, spend on aperture and learn to find your own way around the sky.

Accessories worth buying first

A red torch, so you can read a chart without losing your dark adaptation. A printed star atlas or an app with a red mode. One low-power, wide-field eyepiece. For everything else, wait a few months of use until you know what you really need.

If you are unsure, you can rent a telescope through Sao Viet and try it on a trip before deciding to buy.