Buying a telescope for under £100, what to look out for
Children often ask me about astronomy from their back garden. There is plenty to see even with a starter telescope, although the amount of light pollution can dramatically effect deep sky targets such as galaxies and nebula.
As a keen astronomer for many years I always like to try out the latest offerings. When I started out in the 1970’s the choice was either make your own or spend a large sum of money buying a telescope. Thankfully the new era of modern telescopes allows access to some great entry level instruments for a very small outlay. Three such telescopes are Celestrons Firstscope (£49.99), Travelscope 70 (£59.99) and AstroMaster 70 AZ (£89.00). Below I will give a brief overview of what you can expect for your money.
Before getting down to specifics, there are a few things worth knowing when buying your first telescope. Firstly, do not be attracted by entry level telescope advertising very high magnifications. This is a red herring and may lead to disappointment. To explain briefly, it is the eyepiece that magnifies the image, but the size and quality of the mirror or lens that limits the maximum ‘useable’ magnification. A rough guide is to multiply the size of the optics in mm by 2, to give you maximum useful magnification. For example a 60mm telescope will be good up to around x120 or so, after which the view will only become fainter and less clear.
On an average night in the UK magnifications of 200+ are not often used due the turbulence in the atmosphere. So, if you see a 60mm telescope advertised as having 400x magnification, don’t expect to use it a 400x and have satisfactory views. At this high magnification objects also move across the eyepiece very fast and would be very difficult for a beginner to track (without a motorised mount).
Also, when viewing the planets it is always best to view them when they are at their closest to the earth. A look through the current month of any astronomy magazine will tell you which planets are best placed, or of course an internet search will also provide this information. Finding your way around the sky is also of key importance, either a good star chart or free software such as ‘Stellarium’ are very useful.
One word of warning – Never look directly at the sun, especially through a telescope or binoculars as this can cause permanent damage or blindness. Also, avoid ‘sun filters’ that screw into the eyepiece – these can be very dangerous.
Below is a brief summary of 3 telescopes for under £100. I have kept this short to provide some basic information – please feel free to contact me if you would like more details. Other telescopes are available at this price range, and this is meant as a guide for what you can expect from different types of telescope. Binoculars are also an option when starting out. They are easier to use and great for star clusters, although don’t offer the same views of the moon and planets as a telescope.
This compact telescope packs a punch, is easy to use and very portable. The straight forward dobsonian design is easy for beginners, and enables you to set up on your garden table in seconds.
I have personally tried out all types of telescopes and spent a very enjoyable night testing this one out. There are 2 eyepieces provided, giving x15 and x75 magnification. The highest practical magnification is around x160, should you wish to purchase another eyepiece at a later date.
The Moon has enough detail with craters, rilles, mares etc to keep you occupied for hours. Jupiter’s bands and 4 main moons were visible using the higher magnification available (x75). Although I did not get the chance to view Saturn, it’s rings would be visible at the highest magnification, when the planet is well placed. The lower magnification is ideal for star clusters, such as the Pleiades, or finding the brighter galaxies such as the Andromeda galaxy (which is around 2 million light years away!). This a great way to dip your toe without a large outlay, and have many nights of fun. Also, be realistic in your expectations – no backyard telescope will give views of a Hubble space telescope photograph!
Celestron 70mm Travelscope
The Celestron 70mm Travel Scope is a good low cost unit intended for daytime viewing and casual astronomical observation. The package is light and compact, primarily designed for travel. All components can be stored in the backpack, which has enough room for accessories.
For those keen on the outdoors this telescope is easily carried around and quickly set up for wildlife spotting. With magnifications of x10 and x40 it also good for stargazing in the evening, particularly craters on the Moon and star clusters such as the Pleiades.
The telescope comes with a light weight tripod, so doesn’t need a table top and can be set up anywhere. I like to use this one to demonstrate to the public when we are at shows.
Celestron Astromaster 70AZ
With a sturdy tripod and longer focal length the Astromaster 70AZ offers the highest power of our 3 entry level telescopes, giving x45 and x90 magnification.
The 70mm aperture, long focal-ratio and coated optics provide pleasing views of Jupiter and some of it’s moons. Saturn with it’s rings is easily identifiable and the lunar surface will show a wealth of detail.
With all 3 of these telescopes, a number of the brighter deep-sky targets are also within reach including the Orion nebula, M13 Globular cluster in Hercules and the beautiful double-star Albireo
I hope that this brief introduction has helped. Keep an on our blog for similar tests on binoculars and an introduction to practical astronomy.
Below is an approximation as seen at x40 and x90 magnifications.