As the dark nights creep upon us Christmas approaches and we begin to think about presents, and you may be flummoxed when you little ones spring on you they want a telescope. Astronomy is an expensive hobby when you start looking into telescopes but there is hope, as a starting point you don't need any equipment to enjoy the nights sky and the best meteor shower of the year, the Geminids peaking on the 14th of December of course a YA event is the best way to experience observatory grade telescopes, but if you're still wanting to get your first scope as a present we hope this little blog can help, read on!
The difficulty in buying a telescope for the first time is expectation, images in magazines and websites are a product of hours of stacking and processing and they aren’t anything like what you’ll see through a telescope! There are some things we need to be aware of when purchasing a telescope. Number one what are you hoping to see, number two, magnification, and number three resolution.
And then there are two real categories of things to see in the nights sky. What we'll all near Earth objects, the planets and moon etc and then Deep sky objects. The near-earth objects, although by our standards are not particularly near, astronomically they are our next-door neighbours! They are quite small and reflect light from the sun, as such they can be magnified quite a lot. To work out magnification in a telescope you take the focal length of the telescope and divide it by the focal length of the lens. So a telescope with a focal length of 900mm will come with two eyepieces, usually a 10mm and a 25mm lens. When using the 10mm lens the magnification will be x90, where as when using the 25mm lens the magnification will be x36. The urge is to magnify everything to the absolute max, but resist! Deep sky objects such as nebula in our galaxy and nearby galaxies such as Andromeda, magnification isn’t the issue, the objects are HUGE! This issue now becomes how much of their light can we ‘capture’. The large the opening in the telescope the more light collected and therefore dimmer objects can be viewed (dimmer objects being a galaxy far, far away!) our eyes are similar, in dim conditions our pupils dilate and we collect more light allowing us to see more in the dark. The next consideration is resolution, the bigger the opening then the higher the resolution. What I mean by resolution is if I drew two dots on a wall very close together and made you stand close to them you could resolve them as two points. If I had you walk backwards, eventually you would get to a point where the two dots would appear as one dot. To allow you to ‘resolve’ the dot as two dots I would need to ‘open’ your pupils more! When we look at the moon we can easily resolve the 'Man in the Moon', the Seas, which are large larva flows, this is because they are hundreds of kilometres in diameter. What we can’t resolve are the thousands of craters, they are too close together and too small.
There are many designs of telescope, but the main types you may have come across are
Newtonian, Refractors and Dobsonian and they all have their pros and cons.
Refractors are the typical telescope design we think of when picturing pirates! They rely on glass lenses refracting the light focusing it on our retinas. Refractors are solid, they don’t require adjustment, but because of the glass lenses the cost rises rapidly
Newtonians and Dobsonians are of a similar design, light enters the telescope, reflects of a circular or parabolic mirror back up the tube to a mirror set at 45 degrees which reflects the light into a lensed eye piece. . Dobsonians and Newtonians using mirrors, you can get more telescope for you buck!
So…what size telescope?
Telescopes come in a range of sizes, and size has two components, the opening and the focal length. An opening or aperture of 90mm will give a clear view of the moon and some of the close planets, mars, Jupiter and Venus, but, because of its relatively small aperture mars will appear as a dark red disk, Jupiter will be a grey disk and Venus, well Venus looks like a bluey disk anyway! You won’t be able to discern any surface detail in Mars and Jupiter, Mars’s polar caps and the banding in Jupiter won’t be resolved and the Nebula in Orion could be mistaken for a wisp of cloud, the Galilean Moons of Jupiter however will be just about resolvable. As the aperture increases up towards 5 inches (yes the change in units and use of Imperial is odd) the banding in Jupiter is visible with averted vision and clearer in a dark sky spot and some deeper sky objects can be viewed with the right conditions, The Great Nebular in Orion, the Andromeda Galaxy and a host of star Clusters. Now the problem with Astronomy, it can be an expensive hobby, as we progress towards 8 inches and up, the deepest of deep sky images begin to be within grasp but the price tag drags those objects away again!
Christmas Pressie Ideas:
As a starter, these are our recommendations, they can be passed on to siblings and friends once they have been grown out of. the links are for our friends at Rother Valley Optics.
70mm refractor by Skywatcher
700mm Focal Length
Eyepieces: 10mm & 25mm
76mm Skywatcher mini Dobsonian
300mm Focal Length
Eyepieces: 10mm & 25mm
114mm Newtonian Skywatcher
1000mm Focal Length
Eyepieces: 10mm & 25mm
There is then an alternative, the trusty binoculars, for a relatively smaller outlay a really good pair of 70mm aperture bins can be purchased, these can be used to get to know the seasonal changes in the night sky and can be passed on when you’re convinced your little astronomer is going to take up the hobby and the investment in a telescope is worthwhile!
There are many different variations of telescope and a huge range of budgets available, but be aware, some may appear too good to be true and they most often are. With our continued impact on the environment its so important we conscious when doing our Christmas shopping. If looked after, a telescope will last years and can be passed on to siblings and friends, the very cheap, plastic bodied scopes from toyshops will not last, and more often than not the lenses are made from plastic meaning the image you’ll see will be distorted and potentially put off a budding astronomer and resign your present to the shed and eventually the landfill.
YA Astronomers are keen to help, so if you see something send a pic over and we’ll give you all the advice we can and if you want further recommendation get in touch! To sample the delights of astronomy, check out our events and get to see observatory grade equipment in your community!