Sitka Nature

Over the past couple of years the sun has been in a solar minimum, a consequence of which has been auroras that are only rarely strong enough to be seen from Sitka. Combined with frequently cloudy skies, the northern lights have not been easy to observer around here for quite a while. A couple of days ago, I noticed the aurora forecast from the UAF Geophysical Institute was for active aurora (4 on a scale from 0 to 9), which meant there was a reasonable possibility that there would be some action in the northern skies.

Skies were clear and it was a moonless night, the satellite-based map of northern hemisphere aurora showed high aurora extending over Southeast Alaska, and I heard someone else had seen a burst of activity, so I checked a couple of times and at one point spent a half an hour watching. I never saw anything more than a pale green glow, mostly visible as a slight brightening of the sky behind Gavan Hill. A long camera exposure made the green of the aurora much more visible, though it also resulted in somewhat strange looking trees in shrubs in the foreground, as they were illuminated to varying degrees by neighborhood lights. Although not as dramatic as past shows I’ve seen here, it was nice to see the aurora again. It’s been over 2.5 years since the last time I photographed the northern lights, and I’m pretty sure that was the last time I saw them.

I took a little time while on my way home last night to shoot some pictures of the moon rising over the mountains and Crescent Bay.

With clear weather prevailing in the days prior to and including the winter solstice, it was a good year for observing the sun during the time when the light and warmth we receive from it is a minimum. Many of the things I noticed this year were things I was vaguely aware of before, though I spent a some time trying to improve my understanding.

On the solstice, the sun rose in the southeast at 8:39 am, with sunset occuring in the southwest at 3:21pm, 6 hours and 42 minutes later. The locations of sunrise and sunset are basically 45 degrees south of due east and west respectively. The earliest sunset actually occured a week before solstice, when it was setting at 3:19pm. The two minute gain of afternoon light was more than made up for by five minutes lost in the morning, with sunrise on 14 December occuring at 8:34am, and on 21 December at 8:39am. The latest sunrise, 8:40am, occurs about a week after solstice. It is not until 4 January that the sun rises earlier than on the solstice.

The sun reaches its highest point in the sky when it is due south. This occured south at noon on the solstice when it was 9.6 degrees above the horizon. For comparison, on an equinox, it reaches a maximum of 33 degrees above the horizon with it passing 9.6 degrees at 8:25am and 5:55pm. On the summer solstice the maximum height is 56.5 degrees above the horizon and the equivalent height of winter solstice noon occurs at 5:45am and 8:20pm. The low height of the winter sun gives us long shadows when skies are clear, and the all too familiar dimly lit days when heavy clouds are overhead.

I made extensive use of this handy sunrise/sunset Calculator (which also includes sun altitude and the time when the sun is due south) for this post.