Skywatch with Bill Irwin – Winter 2019

One of the simplest astronomical observations you can make is that the stars, planets,moon, and sun all rise in the east and sink into the west. At the observatory, then, the four directions are different.

Due to earth’s rotation, the stars move 15 degrees an hour. That is about the length of the handle on the Big Dipper or would be about 30 full moon diameters, which is a lot, although I suspect the moon seems larger than it actually is due to its brightness.

You have to be punctual to see objects in the western sky before they disappear. In the east, after the wait for them to rise, the view only gets better as the night wears on, due to the increasing elevation.

The south is generally the best view. We can see the southern stars down to about 38 degrees below the celestial equator from the Cariboo area, although trees and other obstructions limit this to more like 32 degrees. Constellations like Sagittarius and Scorpius don’t get a lot of time above the horizon at this latitude.

Looking up north, anything that is close to the horizon is circumpolar and will eventually be nearly overhead at some time of the year, so not much time spent there unless looking for aurorae. With some telescope types, observing near the zenith or at Polaris is uncomfortable or mechanically difficult. It pays to have an observing partner that is also a chiropractor.

As it is showing up in people’s lives elsewhere, climate change is having its effects on life at the observatory. I have lived here for nine years now, so don’t yet have a personal long-term climate reference for this area. The winters here now do seem comparable to winters in Lillooet back in the late 70s and 80s when I lived there. I remember snow piled up in the middle of main street and waiting for snow to leave driveways in March down there.

The recent wet weather has allowed few clear nights. If the moon is out when you get one, there is weeping and lamenting. Even though the moon has about a million times less light energy per square meter at the earth’s surface than the sun, it is enough to wash out the stars and especially the faint nebulous objects that we have been training ourselves to see. (If you have solar panels, your kilowatts will become milliwatts even at full moon).

We could get a dry period next summer, but that usually ends up with smoke. The increased energy in the atmosphere has compressed the jet stream, folding it like a sidewinder. The contrast and sequencing between weather systems is more dramatic. So maybe we should get into weather watching, get those fancy Davis weather stations and hold a lottery on the extremity of temp or pressure differentials.

Starwatching is worth the wait, however. Mars will be making an increasing presence in the morning sky as the year rolls in, heading towards opposition on October 13, 2020. It won’t be quite as large in diameter this time but its much higher elevation in the sky will more than make up for it.

Mercury will be transiting the sun on November 11, 2019. The mid-transit will be around 7:20 a.m. in Williams Lake and the dot on the sun will take five hours total to cross. You will need special filtering to see it. As usual, we will be set up here for it and you are welcome to join us at Bells Lake Observatory near Horsefly. Email me at or call (250) 620-0596

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