DARK SKIES: Reflecting on the reflector
THE humble Newtonian Reflector invented by Isaac Newton in 1672 uses a large, concave-shaped aluminised or silvered primary mirror at one end of a long tube, to collect and reflect the incoming starlight back up the tube to a small, flat, elliptical-shaped secondary that is tilted 45 degrees.
At this angle the light is passed out to the side of the tube, where an eyepiece magnifies the image formed by the primary mirror.
Reflecting telescopes are not only the most popular for astronomers, they are photographically faster - F2-F8 - making them the prime instrument to image distant galaxies and nebulae in a shorter amount of time.
While the average reflector has a 20cm mirror, many advanced amateur astronomers have telescopes in the 30-100cm range.
The largest reflecting telescope at the moment is the 10 Keck Telescope situated on Mauna Kea in Hawaii.
At an elevation of 4km above sea level, this huge telescope allows astronomers to reach further into space than any other land-based telescope.
Currently, the European Southern Observatory is constructing the world's largest 34m mirror- reflecting telescope on top of the Andes mountains in southern Chile.
Once completed in 2022, this giant telescope, housed in a 100m-diameter dome, will not only be the first remotely operated telescope via satellite and fibre optics, it will clearly image galaxies that the current Hubble Space Telescope shows as smudges.
At the same time, the 6m reflecting James Webb Space Telescope will be 150 times more powerful than the 34m ESO and the HST combined.
For those wanting to buy a telescope, the best all-rounder is a 20cm F6 Newtonian reflector. It's easy to set up and use and it's portable.
It can magnify up to 400 times and can be used to get close-up images of the moon and planets.
Depending on how it's mounted - Alt-Azimuth or Equatorial - with or without a computerised system, expect to pay in the $400-$3000 range.
Those who want a semi-auto GOTO system whereby one selects an object - the moon, a star, planet or galaxy - then presses the GOTO button, the scope will then move to that target, placing it fair and square in the eyepiece or camera.
While this system will allow more to be seen and enjoyable to use, nothing beats learning the night skies the old-fashioned way with a star map and star charts as it was before the digital age.
With so many astro apps these days, I'm surprised there are not more taking up astronomy as a hobby and getting a decent telescope.
With Christmas coming up, if you're contemplating a telescope for the budding astronomer in the family, shop around or contact the observatory for free, non-obligated advice.
If you have an astronomical related question or want to book a stargazing night at the observatory, email firstname.lastname@example.org or phone James on 0427 961 391. Visit www.kingaroy observatory.com.
Next week's topic: telescope mounts.