Want to buy a home telescope? Tips from a professional astronomer to help you choose
02.01.2024 - 04:22
/ tech.hindustantimes.com
While the unaided eye or binoculars can reveal much of the night sky, a telescope reveals so much more. Seeing Saturn's rings or the Moon's craters with your own eyes can be an “oh wow” moment. However, choosing the right telescope can be tricky. There are telescopes with lenses and telescopes with mirrors.
Telescopes that are moved by hand and others that are electronically controlled. Telescopes also come in a range of sizes, with a trade-off between light-gathering power, portability and price.
While there's much to consider, changes in pricing and technology mean spectacular views of the universe are more accessible than just a decade ago.
Aperture is fundamental for telescopes. The bigger the light-collecting lens or mirror, the fainter the objects you can see. Double the aperture from 50mm diameter to 100mm diameter, and the light-collecting area quadruples.
The aperture also limits the level of detail you can see, due to the diffraction (interference) of light.
Again, bigger is better – a larger aperture telescope will produce sharper images than a smaller aperture telescope of comparable design. Earth's turbulent atmosphere also blurs images, which can limit the detail seen when the aperture is more than 150mm.
Sometimes cheaper telescopes are advertised by magnification, but a small telescope with extreme magnification just makes blurry images bigger without revealing more detail.
Should you buy a telescope with a refracting lens or a reflecting mirror? It depends what you want to look at, and your budget.
Refracting telescopes can be good for viewing objects on Earth and in the sky. Refracting telescopes with short focal lengths (where light is brought to a focus near the lens) can be quite compact and good for low magnification views, which is great for sweeping across dark country skies.
However, there are catches. While 70mm aperture refracting telescopes can be quite affordable, bigger refractor telescopes are often more expensive than comparable reflecting telescopes.
Refracting telescopes also suffer from chromatic aberration – where different colours aren't brought to a common focus – and this is particularly noticeable at high magnification when stars get coloured halos. This can be mitigated using complex lens designs, but that adds to the cost.
Reflecting telescopes use mirrors to focus light. These tend to be larger and don't suffer from chromatic aberration.
Dobsonian telescopes have a simple Newtonian optical design and wooden mounts, and are a very cost effective (if sometimes bulky) option for larger apertures. Schmidt-Cassegrain and Maksutov telescopes, which use a combination of lenses and mirrors, are more compact (a big plus), but also more complex and expensive.
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