August Night Sky

The nights are beginning to get longer again, and with this year’s warm summer we can do our observing in shirtsleeves! My first aim in August  is to make the most of our limited opportunities this far north to see the wonderful nebulae in Sagittarius, which is looking directly  towards the galactic centre. Sagittarius is very low in the south as it gets dark, so a good southern horizon with minimal light pollution is needed. Transparent conditions will of course help; good seeing (ie steadiness) is less important for these objects. The 3 highlights are M17 (the Swan or Omega Nebula); M 20 (the Triffid Nebula) and M8 (the Lagoon Nebula) . All 3 are star formation regions, and have nearby or associated open clusters to add to the interest. All 3 can be  seen in binoculars, but larger aperture telescopes offer fascinating detail. This can be enhanced, at least for an alternative view, with an O III filter (sometimes called a nebula filter). Blocking out much of the incoming light might seem a strange thing to do when looking at faint objects in the sky, but only allowing light emitting from energised oxygen in these gas clouds into the light path can have a stunning effect.

I like to get to these objects in the sky by heading south along the Milky Way through Cygnus and  Aquila, then stopping off for a look at M11, the Wild Duck  cluster in Scutum, as a useful waypoint before getting into the Sagittarius nebulae. ( Map below) This is, of course, another area of the sky where the background is so rich and interesting that it is also a pleasure to get lost and just wander!

Nebulae in Sagittarius