Page 49 - BBC Sky at Night Beginners Guide to Astronomy - 2017 UK

WHAT TO USE

LATITUDE

AND LONGITUDE

If you live in a small seconds. A search
town or a rural online for ‘latitude
environment, the longitude conversion’
computer database will bring up myriad
in the Go-To handset sites that will do this. Some Go-To
may not have location Only use the minus scopes, such as
details for your area. sign for latitude if the Meade ETX
In this case you’ll you are south of 90PE, sit on
need to supply the the equator, as it altaz mounts
co-ordinates of your means the southern
latitude and longitude. hemisphere. For
There are plenty of longitude, minus means
websites that make it that the location is
easy to discover these west of the Greenwich
location details. They Meridian, pictured left,
often feature a world so this includes all of
map so you can zoom in and click on your western Britain, North and South America.
location to fi nd your co-ordinates. Parts of Britain east of Greenwich, and all
You may need to convert the latitude of Europe and Australia, have a positive
and longitude of your location from the longitude. Not that these locations need a
decimal version into hours, minutes and plus sign.

setting it up: your location, the date and
the time. With these details keyed in to the THE PROS & CONSS
Go-To, the telescope can correctly orientate
the star charts in its memory. Some Go-To Cons
C
scopes come with a GPS receiver built-in that • The database may contain tens of
•
t
helps with this initiation procedure. thousands of objects, but how many you
cc
Now you’re ready for alignment. Firstly, can see will also depend on the scope’s
oo
optics and seeing conditions.
make sure the tripod and telescope are level.
••
• You need to ensure the battery
If there’s any sloping ground you haven’t
hh
has enough charge for the observing
compensated for, the scope will miss its ses session – once a Go-To scope has
target object. This is especially true for a lost its power there is no way to use
o l
t i
Go-To on an equatorial mount, such as the it manually.
• By not manually scanning the heavens,
Sky-Watcher Explorer 150P. With scopes like • •
and with the scope doing all the locating,
these, you should polar align the mount fi rst. an
y
yo
you may miss chance encounters with
The Go-To system will then ask you to centre
in
intriguing objects.
several alignment stars in the eyepiece. • You need to set up and align a Go-To
When you’ve done this, you’re ready to go. c correctly each time you head out to
Other Go-To scopes, such as the Meade Pros observe, in order for it to accurately
ETX 90PE, are mounted on an altazimuth • In light-polluted skies, it’s easier locate objects. This takes time.
mount – either a single-arm or fork type. to locate objects that you wouldn’t
With an altaz mount, you will need to centre otherwise be able to fi nd if you were
manually star-hopping when the stars
one or two alignment stars in the view. With
might be washed out.
either equatorial or altaz Go-Tos, the more
• Go-Tos are good for taking photos that
stars you align on, the more accurate the are free of star trails, as the scope will
mount will be. This is a consideration that track the movement of the night sky.
becomes particularly important if you’re • If you’re planning to show friends
planning to do any astrophotography. several objects in the night sky, a Go-To is s
fast and effi cient.
Finally, remember that there’s one
• A Go-To database can be updated
essential link in this high-tech chain of
when new comets or supernovae are
technology – batteries. Always carry spares, discovered, so you can fi nd new objects
or consider buying a powerpack to ensure you quickly and easily.
don’t run out of power while observing.
skyatnightmagazine.com 2012 49