These mounts were essential for taking long exposure images with telescopes prior to computers and tend to be relatively heavy.Īlt-azimuth mounts have a vertical and a horizontal axis (how a camera is mounted on a tripod, for example), and tend to be cheaper and lighter than equatorial mounts. Mounts fall into two broad categories.Įquatorial mounts have an axis aligned with Earth's axis, so a single motor can compensate for Earth's rotation. To do this, a telescope needs a mount, which is often sold with the telescope but can also be bought separately. Want to look at a celestial object? You will need to point your telescope in the right direction, keep it steady, and follow the object as it moves across the sky (due to Earth's rotation). How do I find things in the sky? Depends on the mount 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. These tend to be larger and don't suffer from chromatic aberration.ĭobsonian telescopes have a simple Newtonian optical design and wooden mounts, and are a very cost-effective (if sometimes bulky) option for larger apertures. Reflecting telescopes use mirrors to focus light. This can be mitigated using complex lens designs, but that adds to the cost. Refracting telescopes also suffer from chromatic aberration-where different colors aren't brought to a common focus-and this is particularly noticeable at high magnification when stars get colored halos. While 70mm aperture refracting telescopes can be quite affordable, bigger refractor telescopes are often more expensive than comparable reflecting telescopes. 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. Refracting telescopes can be good for viewing objects on Earth and in the sky. Should you buy a telescope with a refracting lens or a reflecting mirror? It depends on what you want to look at, and your budget. Sometimes cheaper telescopes are advertised by magnification, but a small telescope with extreme magnification just makes blurry images bigger without revealing more detail. Earth's turbulent atmosphere also blurs images, which can limit the detail seen when the aperture is more than 150mm. The aperture also limits the level of detail you can see, due to the diffraction (interference) of light.Īgain, bigger is better-a larger aperture telescope will produce sharper images than a smaller aperture telescope of comparable design. Double the aperture from 50mm diameter to 100mm diameter, and the light-collecting area quadruples. The bigger the light-collecting lens or mirror, the fainter the objects you can see. How big should the aperture be?Īperture is fundamental for telescopes. 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. Telescopes also come in a range of sizes, with a trade-off between light-gathering power, portability, and price. Telescopes that are moved by hand and others that are electronically controlled. There are telescopes with lenses and telescopes with mirrors. However, choosing the right telescope can be tricky.

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