AUGUST 2005

[AJE]

AUGUST 2005

August is a great month for Astronomy, for a start it gets dark – which is always a bonus, the temperatures are nice and warm and there are some great objects to view at all levels of observing.

We have the Milky Way, our own galaxy, over head running south through Cygnus. A superb naked eye galaxy in Andromeda and one of the best meteor shows of the year on the 11th / 12th.

If you have a pair of binoculars, scanning through the Milky Way can be very rewarding. A small telescope will open up a wealth of objects, the Ring Nebula(M57) a small planetary nebula in Lyra and a fantastic Globular Cluster in Hercules (M13) that is a sight to behold. There are also numerous other objects visible during this month.

We’ll start with the planets and their visibility during August.

Mercury,

At inferior conjunction with the sun on the 6th and therefore not visible at the beginning of the month, but Mercury moves very quickly around the sun and reaches it’d further point from the sun on the 23rd and will rise in the North East and hour and a half before the sun. Mercury is often hard to find as it’s always low down. But it should be visible if you have a good North East horizon.

Venus,

Is an evening object during August and shining very bright at Magnitude -4. Even through a telescope Venus shows little detail except its phase. Venus, being closer to the sun than earth shows phases in the same way as the moon. So the shorter the time between Sun Rise (or set) and Venus Rise (or set) the slimmer the crescent.

Mars,

Is just starting to make a reappearance after long conjunction with the sun. Mars is currently in Ares and brightens to Magnitude -1 during the month. Rising by 10pm at the end of the month. Even though Mars isn’t as close during this apparition as the last one (1 months ago) being higher in the sky for northern latitudes makes this time round a much better proposition for both visual observations and imaging.

Jupiter,

After the fairly favorable oppositions (for the Northern Hemisphere) of the lst few years, Jupiter has now crossed to well below the celestial equator, and will not be favorable for the north till 2011. This doesn’t mean that Jupiter cannot be observed in the north, just that it’s higher in the sky for those “down under”. This month Jupiter is setting by around 10pm at the beginning and 9pm by the end of the month.

Saturn,

After it’s conjunction with the sun during July, Saturn has now retuned to the morning skies; rising by around 3am at the end of the month. It will be fairly small because it is about as far away from Earth as it gets…

Uranus,

In Aquarius is visible throughout the night during August. It is Magnitude +5.7 and will be visible with the naked eye only under very dark skies. Even modest telescopes will struggle to give any detail visually as it’s only 4 arc seconds in size.

Neptune,

In Capricornus is at opposition during August and will be above the horizon for all the hours of darkness. With a disc size of 2.4 arc seconds, Neptune is tiny.

Pluto,

At magnitude +14 is extremely hard to find. Currently in Serpens Cauda and setting around 1am. The only way to be sure that you have observed Pluto is to find where it is supposed to be and take two images several weeks apart and then find the “Star” that moved.

The Moon.

If you observe / image Deep Sky Objects (galaxies, nebula etc) then the moon is a major obstacle. You can guarantee that any really good clear nights that you get will be around full moon, when the moons glare washes out most of the fainter objects.

New Moon is on the 5th August,

First Quarter on the 13th,

Full on the 19th and

Last Quarter on the 26th.

The moon is actually favorable this year for the Perseid Meteor shower (maximum on the 12th).

The Sun.

YOU MUST NEVER OBSERVE THE SUN WITHOUT A PROPER SOLAR FILTER – YOU WILL GO BLIND INSTANTLY.

The sun can be a fascinating object to watch, Sun Spots are the most commonly observed phenomenon. The sun has a cycle of activity and we are currently at the lower end of activity, having said that there have been several really big sun spot groups over the last few months – some of which have caused Aurora to quite southerly latitudes. So it’s always worth keeping you ear to the ground.

Other Events.

The other main event of August is the annual Perseid Meteor Shower. This occurs at the same time each year, over the nights of the 11th and 14th of August. Although it is generally regarded as being the best on the 11th and 12th (specifically early hours of the morning on the 12th). The moon at First Quarter on the 13th means that a bright moon will not hinder observations of fainter meteors. I would suggest dragging out the deck chair on either of these nights and just sitting back and looking up. I normally expect to see around 1 meteor every few minutes (the official figure is 60+ and hour), but experience tells me that isn’t always the case.

This is one area of astronomy that doesn’t benefit in any way from having a telescope or binoculars – just sit back an enjoy! Remember to allow time for your eyes to adapt to the dark and try to avoid going into a lit room. I normally go out from around 9:30pm and let my eyes adapt slowly to the disappearing twilight, it’s normally dark enough by 10pm to start seeing the brighter meteors – there are, almost always, more meteors after midnight than before. One last thing remember to wear a jumper or something similar as after several hours of inactivity in can get quite chilly at 2am!

The map below shows the radient (where the meteors appear to come from. This IMO isn't the best place to look. For me I usually observe straight over head till around midnight then switch my attention to the Square of Pegasus

Constellations, I thought we could have a look at the Summer Triangle for this months guide. The summer triangle is made up from the stars Vega (Lyra), Deneb (Cygnus) and Altair (Aquila). Although the summer triangle isn't actually over head in the evening till well into september it's called the sunner triangle because it is june and july that this "triangle" is visible all night.

Now I'm not going to go into to much detail on this. But there is a wealth of naked eye / binocular / telescopic objects contained within this area of sky. Below is a map of the area and a small list of some of the brighter objects. Included in this list is the size and brightness of the objects - this should give you a good idea of overall surface brightness. For example, the Ring Nebula is faint and small so this is actually really easy to find because it has a high average surface brightness; where as NGC 7000 is bright (mag4) but it is also huge at 3.1 degrees and therefore has a very low surface brightness.