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
Mars remains the most visible planet at the moment. It is prominently placed
almost overhead. Mercury and Venus can be seen as evening stars, setting after
the Sun. Venus will be visible up to 90 minutes after sunset. Jupiter and Saturn
are not visible at the moment.
Question 5: Observation of Mars
Find Mars and determine what constellation it is currently in. Mark this on
the appropriate sky chart. Set your telescope on Mars, using first the finder
telescope to locate it and bring it into the field of view of the main telescope.
Experiment with the different eyepieces, starting with the longest one, to get
the best view of Mars.
Describe/sketch your view of Mars. How does the view change with different eyepieces? If you get to see Mars on both classes describe any changes you see. How does the colour compare as seen through the telescope to your naked eye? Are they the same?
Defocus the telescope and describe what happens to Mars's image?
Sometime during the class you will be able to view Mars through the C14 telescope. Comment on how this view compares with that seen through the C8 telescope?
(d) The Moon
The Moon is Full on October 10 and November 9. Before Full Moon it may be seen
as a waxing (i.e. growing) 'gibbous' Moon, rising in the Eastern sky. New Moon
is on 25 October and 24 of 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 November 9 (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 the event.
Question 6: 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.
Question 7: 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. 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:
Question 8: Describe any other objects you observed.