General Education 4001 Astronomy

Night Laboratory Worksheet

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-west, and the other south. 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

Jupiter is the only planet visible at the moment, though there has been a feast of planets to see over the past month. Jupiter is prominently placed in the northern sky. Mercury and Venus are too close to the Sun to be seen during the class. Mars and Saturn and visible at the very start of the night, but have set in the west by 7pm.

Question 5: Observation of Jupiter
Find Jupiter and determine what constellation it is currently in. Mark its position on the sky map. Set your telescope on Jupiter, 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 Jupiter.

Describe/sketch your view of Jupiter with specific reference to (i) the disk of the planet and (ii) its system of Moons. How does the view change with different eyepieces? If you get to see Jupiter on both classes describe any changes you see.

Defocus the telescope and describe what happens to Jupiter's image.

Sometime during the class you will be able to view Jupiter through the C14 telescope. Comment on how this view compares with that seen through the C8 telescope.

(d) The Transit of Venus

Venus passes across the face of the Sun on the late afternoon of Tuesday June 8th. This is a rare event - the last time such a transit occurred was 120 years ago, so no one living today has seen such an event. The Transit of Venus brought Captain Cook to Tahiti in 1769, and in his subsequent voyage he ran into the east coast of Australia, leading to European settlement of the country 9 years later. A special event is being held to celebrate the Transit of Venus and its historical connection with the Australia - ask your tutor for details!

(e) The Moon
The Moon is Full on June 3. Before Full Moon it may be seen as a waxing (i.e. growing) 'gibbous' Moon, rising in the Eastern sky. New Moon is on 19 May and 18 June. 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 was an eclipse of the Moon on May 5 (the same day as Full Moon - why is this the case?).

Jupiter will be 4 degrees from the Moon on May 27.

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?

(f) Stars
Observation of the Southern Cross and the Pointers

Question 7: Set your telescope on the lower most Pointer (to the SE); this is Alpha Centauri. Describe what particular feature of this object you are able to discern with a telescope that is impossible to see with the naked eye. Determine the order that the 5 brightest stars of the Southern Cross are arranged in. Locate Alpha Crux and describe how it looks through the telescope. How might one use the Pointers and the Southern Cross to find South? Describe your observations of these objects.

Orion and Scorpius
Orion, the Great Hunter is setting in the west, while Scorpius is rising in the East. Do you know the mythology of these constellations and why they are in opposite parts of the sky? Locate the 3 Belt stars of Orion and the Orion Nebula above them, half way to the brilliant Rigel. Find Sirius, the brightest star in the sky. Locate Scorpius by its hook-shaped tail. Antares is the bright red star in the tail of Scorpius.

Question 8: Describe what you see associated with these two constellations.

(g) Comets

Two comets are visible in the skies in May and June: Comet NEAT and Comet LINEAR. This is a rae event! NEAT is well placed for vieiwing in early May, and LINEAR in late May and June. See if you can find one of these comets in the Northern sky and describe what you see.

(g) 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:

• choose an object to observe,
• consult a sky atlas to find whether it is accessible (you could use TheSky planetarium software with the C14 for this),
• identify on the sky atlas 'landmark' objects to help find your way to the target, and
• locate and observe your object with the telescope.

Some objects you might observe include:

• The 'Jewel Box' open star cluster in the Southern Cross.
• The Milky Way.
• The globular clusters 47 Tucanae (near the SMC) and Omega Centauri (near the Pointers).
• The centre of our Galaxy.
• Eta Carina, midway between the Southern Cross and the 'False Cross' (to its west).
• The Eta Aquarids meteor shower peaks on May 5. You may be lucky enough to se a few shooting stars around this date. They are specks of dust which originally were part of Halley's comet.

Question 9: Describe any other objects you observed.