- 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.
- Telescopes also come in a range of sizes, with a trade-off between light-gathering power, portability and price.
How big should the aperture be?
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.
- 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.
Refractor or reflector?
- Refracting telescopes Refracting telescopes can be good for viewing objects on Earth and in the sky.
- While 70mm aperture refracting telescopes can be quite affordable, bigger refractor telescopes are often more expensive than comparable reflecting telescopes.
- Reflecting telescopes Reflecting telescopes use mirrors to focus light.
How do I find things in the sky? Depends on the mount
- To do this, a telescope needs a mount, which is often sold with the telescope but can also be bought separately.
- Equatorial mounts have an axis aligned with Earth’s axis, so a single motor can compensate for Earth’s rotation.
- With the advent of cheap computing, they can now be used to automatically point at and track celestial objects.
- A completely manual telescope will be cheaper than a telescope with automation, but you will need to navigate the sky yourself.
Do I need a finder scope?
- A finder scope with a wider view and crosshairs simplifies things.
- Even telescopes with goto electronics often need to be calibrated with bright stars and locating them is easier with a finder scope.
What about the eyepiece?
- Sometimes decent telescopes are sold with quite cheap eyepieces, but it can be relatively inexpensive to upgrade to a better one.
- More complex eyepieces that provide better views are also available, and far cheaper than they once were.
What if I want to take astro photos?
Taking basic astronomical photos has become much easier with smartphones. While you can hold a phone to the telescope eyepiece for a photo of the Moon or a planet, you will get better results with an adapter that holds your phone securely in place.
- For long exposures, automatic tracking of celestial objects is essential, and that adds to a telescope’s price.
- However, you do lose the experience of seeing the universe directly with your own eyes through the eyepiece.
Try before you buy!
- There should be plenty of telescopes, and owners happy to wax lyrical about them.
- A specialist shop can also give a direct experience of a telescope: its size and how it works (with limitations during daytime).
- For example, you may find a telescope is too bulky or technical for your needs.
Michael J. I. Brown receives research funding from the Australian Research Council and Monash University.
