Write your Name, Student ID and Tutorial Group number on a separate piece
of paper and answer the following questions:
(a) Telescope Design and Operation
Your tutor will explain the basic principles and operation of an astronomical
telescope.
Question 1: Of what significance is the diameter of a telescope's primary mirror?
Question 2: What is the advantage / purpose of an equatorial mount and, in this context, explain how the telescope tracks objects across the sky?
Question 3: The visual observations you will make will use an eyepiece mounted at the Cassegrain focus of the telescope. Sketch the path light from an astronomical source takes to reach this focus.
(b) Alignment and Focus of the C8 Telescope and its Finder
In your group, using one of the C8 telescopes, carry out the following steps
(your tutor will assist you and will also verify that the important steps
have been completed successfully):
Choose a suitable distant (artificial) light source on the horizon.
Making sure the telescope tracking is turned off, bring the source into the field of view of the main telescope eyepiece. In doing so you will need to bring the telescope into focus using the adjustment knob at the bottom of the telescope (adjacent to the eyepiece). Centre the source in the field and lock the telescope in this position by clamping both axes.
Now view the distant source through the small finder telescope. By adjusting the mounting screws for the finder telescope, locate the source on the centre of the finder's bulls-eye target. Both the finder telescope and the main telescope should now be aligned.
Question 4: in terms of orientation, how does the image seen through the telescope compare to that when viewed directly?
You have been given sky charts showing the positions of the stars and planets at this time of year. One chart is looking north, another south and the third overhead. To use them hold them overhead and orientate them with the compass directions (South is towards Barker Street and Botany Bay). Constellations are shown by lines connecting stars. The astronomical coordinate system is marked on the sky, measuring position in hours and degrees. See if you can identify in the sky some of the planets and stars named on the charts (note that the planets are not marked on the maps - you have to find them for yourself!).
(c)The Planets
Unfortunately there are no planets visible at the moment! This is unusual, and
your Course Authority apologises to you, but asks you to take the matter to
Higher Authority if you are unhappy with the arrangement of the planets in the
sky at the moment. Normally there would be at least one planet visible for you
to look at. Mercury is visible for a short time after sunset. Saturn will be
rising in the east around midnight, and Venus will be a bright star in the east
before the Sun rises (the "Morning Star"). There is going to be a
partial Solar eclipse at 2pm on October 14. However the region of partial eclipse
is in the northern hemisphere, and we will not see any of the eclipse from Sydney.
(d) The Moon
The Moon is Full on October 28. Before Full Moon it may be seen as a waxing
(i.e. growing) 'gibbous' Moon, rising in the Eastern sky. New Moon is on 14
October and 13 November. After New Moon it may be seen as a waxing crescent,
setting in the Western Sky. The best time to observe the Moon is a few days
after New Moon, before it gets too bright. There will be an eclipse of the Moon
on October 28 at 1pm (the same day as Full Moon - why is this the case?). Unfortunately
the Moon will be below the horizon for us when this occurs, so we will not see
this eclipse either (blame Higher Authority!).
Question 5: If you can see the Moon study it through the telescope. Draw what you see. What happens as you change the eyepiece? What part of the Moon is it easiest to observe?
(e) Stars
Observation of the Southern Cross and the Pointers
The Southern Cross is poorly situated for viewing at this time of the year,
but see if you can find it and the nearby Pointers. Set your telescope on the
upper most (and brightest) of the two Pointers (in the SW); this is Alpha Centauri.
It is the nearest star to us in the sky after the Sun. The Southern Cross is
below the Pointers, in the murk. Try and locate Alpha Crux, the brightest star
in the Cross, lying at its foot.
Question 6: Describe what particular feature Alpha Centauri
you are able to discern with a telescope that is impossible to see with the
naked eye. How far away is Alpha Centauri? Determine the order the 5 brightest
stars of the Southern Cross are arranged in. How does Alpha Crux look through
the telescope? How might one use the Pointers and the Southern Cross to find
South?
Observation of Achernar and the Magellanic Clouds
The bright star Achernar lies directly the other side of the South Celestial
Pole from the Cross, and is well placed for observation. The Pole is roughly
mid-way between Alpha Crux and Achernar. Between Achernar and the Pole lie the
Large and Small Magellanic Clouds, two satellite galaxies of ours. Can you find
these galaxies? This is hard, but from a dark site they stand out clearly like
two wispy clouds in the sky.
Observation of Scorpius
Scorpius is setting towards the west, but is still well-placed for viewing.
Locate it by its hook-shaped tail. Find Antares, the prominent red star. It
is sometimes known as the Eye of the Scorpion. Describe anything you see.
(f) Optional Observations of Additional Objects (depending on
time / weather availability)
There are many other objects in the sky that you could observe (e.g. other stars,
stars clusters, globular clusters, emission and reflection nebulae, other galaxies).
To do so you (in consultation with your tutor) will need to:
Some objects you might observe include (refer to your sky chart as well):
Question 7: Describe any other objects you observed.