Page 52 - BBC Sky at Night Beginners Guide to Astronomy - 2017 UK

CHOOSING

AN EYEPIECE

MAKE SURE Which is more important: the telescope or the near the eyepiece end, by the focal length of the
eyepiece. The focal length of any decent eyepiece
eyepiece? The telescope gets lots of attention
YOU GET THE because it’s the most expensive and impressive- will be marked in millimetres around its collar.
BEST VIEW OF looking part of your setup – but without decent So for example, to work out the magnifi cation of
THE NIGHT SKY eyepieces, the views you get can be disappointing. an 800mm focal length telescope with a standard
25mm focal length eyepiece, you divide 800 by 25,
What you ideally want is a good range of
BY USING THE eyepieces, because different sizes of focal length which is 32. This setup will magnify objects you
RIGHT EYEPIECE are useful in producing better views of different see in the eyepiece by a factor of 32.
kinds of objects. This is due to the fact that each For wider views of nebulae and star clusters,
eyepiece will have a differing fi eld of view and this is the kind of number you will want. With
magnifi cation, depending on the telescope used. higher magnifi cations, maybe with a 10mm
To fi nd out what magnifi cation eyepiece, you’ll get more detailed views of the
you’re getting with any eyepiece planets and double stars.
takes a very easy calculation – you As you progress in astronomy, you will
simply divide the focal length undoubtedly start to experiment with the different
of the telescope, which is views that a range of eyepieces can offer. So
usually printed on a make sure you don’t underestimate these small,
label on the scope seemingly insignifi cant bits of astro equipment!

PAUL WHITFIELD X 4 , STUIDO4PHOTO, TELE VUE, WILL GATER

52 skyatnightmagazine.com 2012