Notes · Telescopes
Choosing Your First Telescope in New Zealand
The most common question any astronomy society hears is "what telescope should I buy?" The honest answer is that the best telescope is the one you will actually carry outside, and that a modest instrument used often beats an expensive one gathering dust in the hallway. With that in mind, here is how we would approach it.
Start with binoculars
Before spending serious money, borrow or buy a pair of 7x50 or 10x50 binoculars. They are cheap, quick to use and teach you the sky in a way a telescope never will. From New Zealand they show the Magellanic Clouds, the star fields of Carina and Crux, the Jewel Box as a tight knot of stars, the moons of Jupiter and the craters along the moon's terminator.
Binoculars also answer an important question: do you enjoy being outside at night, finding things? If you do, a telescope will be a joy. If not, you have spent very little finding out.
Aperture is king, within reason
The single most important number on a telescope is aperture, the diameter of the main lens or mirror. Bigger aperture gathers more light, shows fainter objects and resolves finer detail. Magnification is far less important, and boxes boasting "500x" are a warning sign. Useful magnification tops out at around twice the aperture in millimetres, and the atmosphere limits most nights to 150x to 250x anyway.
The three main designs
Dobsonian reflectors
A Dobsonian is a Newtonian reflector on a simple rocking box mount that you push around by hand. It gives the most aperture per dollar by a wide margin. A 150 mm (6 inch) or 200 mm (8 inch) Dobsonian is the classic first serious telescope and will keep you busy for years.
- Strengths: big aperture, very stable, simple, cheap to run.
- Weaknesses: bulky, the tube needs occasional collimation (mirror alignment, easy once learned), and not suited to long-exposure photography.
Refractors
A refractor uses a lens at the front. Small refractors of 70 to 100 mm are light, need no collimation and cool down quickly, which makes them great grab-and-go instruments. Good apochromatic refractors give beautiful sharp views but cost much more per millimetre of aperture. Cheap achromats show a purple fringe around bright objects, which is not a disaster for the moon and planets but is noticeable.
Schmidt-Cassegrains (SCTs) and Maksutovs
These are compact catadioptric designs that fold a long focal length into a short tube. They usually come on computerised "go-to" mounts. They are excellent for the moon, planets and double stars, and portable for their aperture. On the downside they are more expensive, slower to cool, and their narrow field of view is less suited to the big, sprawling objects that the southern sky does so well.
The mount matters as much as the optics
A wobbly mount ruins a good telescope. If the image shakes for three seconds every time you touch the focuser, you will give up. Be very wary of cheap telescopes on thin aluminium tripods. A Dobsonian base is wonderfully steady; for other designs, look for a solid equatorial or alt-azimuth mount rated well above the telescope's weight.
Go-to mounts are convenient, but they need power, an alignment routine and a bit of patience. Many experienced observers suggest learning the sky the old way first, with a good star chart or an app like Stellarium, then adding electronics later if you want them.
Buying secondhand
New Zealand's market is small and imported gear is not cheap, so secondhand is well worth considering. Optics last for decades if looked after. Local astronomy societies are the best place to start: members often sell equipment when they upgrade, and they will happily let you look through different telescopes at a public viewing night before you decide. The Royal Astronomical Society of New Zealand lists affiliated societies around the country, and in the capital the Wellington Astronomical Society runs regular events.
When checking a used telescope, look for scratched or fungus-spotted optics, missing parts, and a mount that holds position without creep. Mirrors can be recoated; fungus inside a lens is harder to fix.
Southern targets that make it all worthwhile
The southern sky has some of the finest objects in the heavens, and many of them are invisible or very low from Europe and North America.
| Object | What you'll see | Best in the evening |
|---|---|---|
| Eta Carinae Nebula (NGC 3372) | Vast glowing nebula with a dark lane, bright even in small scopes | Autumn |
| Omega Centauri (NGC 5139) | The finest globular cluster in the sky, resolving into thousands of stars | Autumn to winter |
| 47 Tucanae (NGC 104) | Brilliant globular next to the Small Magellanic Cloud, with a blazing core | Spring to summer |
| Jewel Box (NGC 4755) | Compact cluster of coloured stars beside Beta Crucis | Autumn |
| Large Magellanic Cloud | Galaxy full of clusters and nebulae, including the Tarantula | Summer |
| Small Magellanic Cloud | Smaller companion galaxy, with NGC 362 nearby | Spring to summer |
Many of these are circumpolar from most of the country, so they are above the horizon all year and simply higher in some seasons than others.
Don't forget the familiar targets either. Saturn's rings and Jupiter's cloud belts are thrilling in any telescope, and our planets page and moon page have more on what to look for.
A sensible first purchase
If we had to give a single answer: a 150 or 200 mm Dobsonian, a low-power eyepiece with a wide field, a red torch and a planisphere set for about 40 degrees south. That combination shows thousands of objects and will never feel like a waste. And one rule that never changes: never point any telescope or binoculars at the sun without a proper, certified solar filter fitted over the front.