The following describes objects in our night sky for August and is especially written for beginning observers.
If you do not own a telescope, the club Observatory has a 100mm aperture high quality refractor that is perfect for your use. It is probably a better telescope than most of us ever started Amateur Astronomy with.
Don’t be scared to use what is your Observatory as a club member. Visual use of the Observatory’s 100mm telescope is the entry level and is not difficult. Contact Mark Town for training. If you have already undergone the training and would like a refresher, arrange to book the Observatory with myself or Mark or another member of the club who is experienced with the facility.
Contact Text Email
Mark Town 0474 859 788 marktown@shoal.net.au
Andrew Wood 0401 907 025 amwood1961@outlook.com
More about Observatory use later.
The Moon
The Deep Sky Objects described later should be visible with the Moon present, although they will be better seen at times when the Moon is not visible. Still, don’t be put off by the Moon for your first Observatory visits. The Moon is the best object to start with for new observers.
Moon Phases
Aug 1: First Quarter – the Moon rises about midday and sets about midnight. Afterwards, it waxes through gibbous phases toward…
Aug 9: Full Moon – rising about sunset and visible all night. Afterwards, it wanes through gibbous phases toward…
Aug 16: Last Quarter – rising around midnight. Afterwards, it wanes through crescent phases toward…
Aug 23: New Moon – rising and setting with the Sun. No moon visible all night. Afterwards, it waxes through crescent phases toward…
Aug 31: First Quarter. A second occurrence of the phase this month.
Planets
Planetary observing is only for early risers or those staying up late this month.
Venus and Jupiter, the two brightest planets, will appear close in the sky in the east about 40 minutes before Sunrise. On August 12 and 13 they will be only 1 degree apart. This will be a good naked-eye view. A telescope will show Venus as a gibbous phase. Jupiter will have up to four of its moons visible, and some surface markings may be apparent on the planet.
Saturn rises around 8:30PM. It would be best to wait until 10PM when it is well above the eastern horizon. August 12 sees the planet close to the gibbous Moon a few days past full. A telescope will show the planet’s rings, currently nearly edge-on from our perspective. Titan, the biggest of Saturn’s moons, will be visible in a small telescope. Surface features will require a larger telescope.
Deep Sky Objects
Refer to the article: DEEP SKY 101 | Shoalhaven Astronomers on this website for information about the types of Deep Sky Objects.
The picture below shows an area near the Southern Cross at 8PM during August. A good area of sky to start observing these types of objects in the southern hemisphere. [The picture was created in a free program, Stellarium, which can be downloaded from the internet].
The following are descriptions of the numbered objects [see the end of this article for a primer on terms such as magnitude and NGC]
- Alpha-Centauri is the brightest star in the constellation Centaurus. It is a Double Star. If using the 100m refractor at our Observatory, bring the star to the centre of the field using the 42mm eyepiece. Then change to one of the 8 or 9mm eyepieces in the accessories box. This will greatly increase the magnification. The star will now resolve into two separate stars. The magnitude of the brighter star is 0.0. the fainter is magnitude 1.2. This system of 2 stars is 4 Light Years away.
- Acrux, or Alpha-Crucis, the brightest star in the Southern Cross, is a Triple Star. When first found at low power, the bright star will have a much fainter star nearby. Increasing the magnification will now resolve the bright star into two. The magnitudes of the three stars are 1.3, 1.7 and 4.9. This system of 3 stars is 323 Light Years away.
- The Jewel Box, also called NGC 4755, is an Open Star Cluster, close to Mimosa, or Beta-Crucis. At low magnification, a small A-shaped group of stars is visible. Increasing the magnification reveals many more stars, some coloured. The magnitude of the cluster is 4.2, and it is 81 Light Years away.
- Omega Centauri, also called NGC 5139, is a Globular Cluster. Low magnification will show a round cloudy mass. Increasing the power will reveal thousands of stars. Clusters such as this contain hundreds of thousands of stars. This cluster has a magnitude of 3.9 and is 17,000 Light Years away.
- The Blue Planetary, also called NGC 3918, is a Planetary Nebula. It is the faintest object in this list and will be easier to see with no moon visible. At low power, look for a star more than a pinpoint, slightly more spherical. Increasing magnification will show the spherical nature more clearly. This is a dying star losing its matter to surrounding space. It is magnitude 8.1 and 31 Light Year away.
- Centaurus A, also called NGC 5128, is a Galaxy far distant from our own Milky Way galaxy. It is 14,000,000 Light Years away. Although bright at magnitude 6.8, once again it will be better with no moon visible. At low power, look for a fuzzy patch of light. Higher magnification will reveal a round mass with a dark lane through the middle. Akin to a hamburger.
- The Eta Carina Nebula, also called NGC 3372, is an Emission Nebula. I have left it until last because by 8PM it may be a little low, though you could observe it first or start at 7PM. The low power eyepiece in the Observatory will show the cloudy nebula and dark lanes well. Higher magnification will show the orange star Eta-Carina, with lobes either side. This star, like object 5, shows the mass loss of a Planetary Nebula. Eta Carina is 6,000 Light Years away. Like many large emission nebulae, it is not assigned a magnitude.
Having seen these objects through the 100mm refractor in the Observatory, you may want to use a larger aperture telescope for better views. A larger aperture will collect more light and more detail. Inside the Observatory are stored two 200mm telescopes. Learn how to use these telescopes – just ask. They can be used in the area outside the Observatory and can also be borrowed for you to take home.
Notes on Observatory Use
- After dark the university campus is quite empty. I have left very late with no other cars in the car park. This can be daunting and also is a safety issue if you have a fall or other event. It is probably best to have someone with you. On the other hand, it is highly unlikely anyone posing danger will be present, and if you are confident to be able to use the Observatory alone, be careful.
- For Deep Sky Observing, the entry level use is using the hand-controller to move the telescope to objects, then use the dome control to shift the dome so the telescope can see out. The next level is to use the computer to control the telescope and dome. The computer gives out a lot of light, affecting your night vision. For visual observing it is best to close the Observatory entrance to keep the campus lights out, leave the computer off, and use the hand controls. This will mean obtaining a …
- Red-light torch. With all the lights out to preserve your night vision, you will still need to see to move safely around inside the Observatory. Astronomers use red light, which in the visible light spectrum has the lowest energy, to preserve what we call Dark Adaptation. The Observatory does not have a red-light torch; you should bring one with you. Torches with red LEDs can be purchased or get a small torch and tape several layers of red cellophane over the globe.
- Here’s a practical consideration – the Observatory has no toilet, it’s quite a walk to the campus buildings in the dark, and they are probably closed anyway. Make sure you have gone beforehand, and if you are there a long time, you’ll have to use the good old “bush toilet” near the observatory if it becomes necessary. Once again, take care.
- To take refreshment such as water or coffee, or eat snacks, go outside the Observatory.
Some Useful Terms
Aperture is the diameter of the lens or mirror that the telescope uses to collect light.
Magnitude is how bright an object is. Smaller Numbers have Brighter Magnitudes – e.g. Magnitude 1 is brighter than magnitude 2. A very dark sky will allow stars as faint as magnitude 6 to be visible. Very bright objects – bright stars and planets, the Moon and Sun, have negative magnitudes.
Magnification, or Power, is calculated by dividing the focal length of a telescope by the focal length of the eyepiece being used. The 100mm refracting telescope in the Observatory has a focal length of 550mm. The 42mm eyepiece that is in the telescope when you enter the Observatory yields a magnitude of 550/42 = 13. This gives a very wide field of view to locate the object. Exchanging for eyepieces with shorter focal lengths increases the magnification, enabling more detail to be seen. An 8mm eyepiece in our telescope will give nearly 70X magnification.
NGC stands for New General Catalogue. All Deep Sky Objects will have a catalogue number, of which the NGC is the most well-known, with more than 7,000 objects. Many brighter, more well-known objects have names such as Jewel Box, Blue Planetary etc. All of these will also have a number in one of the many astronomical catalogues.
FOR THOSE NEW TO AMATEUR ASTRONOMY
I strongly advise that you purchase or borrow books, or read online sites, devoted to teaching basic Astronomy. Teach yourself about
- Different types of telescopes
- Aperture and Focal Length
- Magnification
- Eyepieces, Barlow lenses and filters
- Navigating the night sky
- Planispheres
- Star Atlases
- Right Ascension and Declination
- Deep Sky Objects – clusters, nebulae and galaxies
Andrew Wood