The Sky for August 2013

Now that we are into August astronomical twilight starts at about 10pm EDT with dawn is around 4am EDT. This means being able to get outside to see some interesting stuff before bedtime and ample time to set up an imaging run. Identifying constellations and locating bright stars can be done shortly after nautical twilight which starts about 9:15pm EDT. Finder_Chart-Sagittarius_2013-08-17

The main feature of the sky in August and September is the Milky Way. In August it’s due south at 10pm with the brightest section – the Ophiuchus bulge – quite prominent. If observing for a moderately dark site, look for the dark  lane that runs down the middle.

Sagittarius is due south near the horizon. The galactic centre is about 1° south of 3 Sagittarii. Look there and you are looking at the “black hole” that lies at the centre of our galaxy.

This section of the milky way has several excellent binocular or small telescope targets. Using binoculars or a small scope, just scan up the Milky Way and you will see several interesting fuzzy objects (also known as deep sky objects – DSOs). A few noteworthy objects to look for are:

  • Lagoon Nebula (M8) – can sometimes be seen unaided. A small telescope will reveal a very bright patch with some dark lanes.
  • Trifid Nebula (M20) – Physically connected to M8, it’s a little harder to see due to its red colour. Look for the open cluster M21 just a little to the north east in the same binocular FoV.
  • Sagittarius Cluster (M22) – a mag 6.5 globular cluster which ranks as the third brightest in the sky.

Finder_Chart-Zenith_2013-08-17 At the zenith three easy to identify constellations stretch from east to west – Cygnus, Lyra and Hercules. Don’t forget to look for Delphinus (the Dolphin) – the small diamond shaped constellation near the ecliptic.

Hercules is home to two of the brightest globular clusters – The Hercules Cluster (M13) and M92. M13 is mag 7 and large enough to be seen unaided from a dark sky (limiting mag 5+). M92 will require binoculars.

Finder_Chart_Lyra The Ring Nebula (M57) is located in the south part of Lyra and is an excellent planetary nebula to view in small scopes. It’s only mag 9.5 so requires fairly dark skies, But at 1.7′ across, it’s large for a planetary nebula.

Just to the east of Vega in Lyra is Epsilon Lyra (ε) the “double double” – a multiple star system consisting of 4 stars arranged in two pairs.

Finder_Chart_Epsilon-Lyra
The two pairs have a separation of 3.5′ which can be seen in binoculars. The pairs have separations of 1.3″ and 2.3″ making them challenging doubles to split in a 4″ scope. However, the two pairs are oriented 90° with respect to each other making it easy to compare the star shapes and aiding in detecting the separation.

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  1. Pingback: Observing Report – 2013-08-17 | Denholm Observatory

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