The natural Navigation: The Right Course, Naturally

For much of the UK, tonight promises to be a good night for some stargazing. With a bit of luck the only clouds for many will be from our breath. The moon, which is four days off full, will outshine many of the stars but should not spoil the party.

If the sky is clear we will get a very good view of Mars in the east in the early evening. Sitting between the constellations of Leo (easy to find) and Cancer (hard to find), it will be rising about thirty degrees north of east at dusk and pass through due east at 8.30pm. By then Orion, below the high moon, will have moved to occupy a large part of the southern sky. If you follow Orion’s belt down to nearer the horizon then low in the southeast you will see the brightest star of them all, Sirius.

If you do happen to…

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Venus and Sirius both beamed at me this morning during my pre-dawn shiver outside. The aircraft were painting a pink path to the continent to escape the autumnal cold. They are of course heading southeast, which I’m sure you checked from the tiny crescent of the moon. Speaking of crescents, this morning calls for a hot croissant.

Happy Summer Solstice everyone. Sunrise and sunset will be closer to north than east or west at this time of year for most of Scotland.

This photo is taken looking southeast. The setting sunlight can be seen bouncing off the northwestern edges of the clouds.

This morning’s sun was a strong enough clue, but if we wanted to know which way was southeast then these aircraft contrails are pointing the way to the continent.

It looks like a particularly busy morning for aircraft, but this is just a reflection of atmospheric conditions. The hydrogen-rich jet fuel has mixed with oxygen, reacted in the engines and formed, among lots of other lovely and not so lovely things, water. In certain temperatures and humidity levels this water freezes into ice crystals. The high cirrus clouds that we normally see are also composed entirely of ice.

The length of time that a contrail survives depends on the humidity, if the air is dry it will sublimate away, but if saturated they will last as long as other cirrus clouds.

My wife and I spent nearly all the weekend on the water, which will be a rare treat until our boys are a bit older. There was lots of sun, plenty of mist and fog and not very much wind. It would have been nice to have done more sailing and less motoring, but we were ecstatic just to be out there.

In my last entry I talked about dawn and dusk colours, these two dawn pictures show the shift in colour quite nicely. There was only one minute between the two shots. Interestingly it appears to have reddened, which is not what we’d usually expect to see – ah, nature, that slippery friend!

Natural navigators will have spotted already the windswept nature of the trees on the shoreline, confirming that we are indeed looking southeast.