Venus meets the crescent moon

CORONAVIRUS travel restrictions have limited my recent stargazing adventures to walking distance from my house. You might think this would restrict my astronomical activities but, in fact, I've found the opposite to be true.

I've had some wonderful celestial experiences in lockdown.

This is because, luckily, my Portobello garden has a view to the west across Otago Harbour. This means over recent weeks, I've been able to enjoy the nightly motion of Venus as the sky darkens after sunset. With Venus setting roughly 90 minutes after the sun, there's a relatively brief viewing window every night.

Next week, the waxing crescent moon joins Venus in the northwestern sky. On Sunday, the 9% illuminated crescent will be to the left of Venus. The pair should make a beautiful sight in the gathering dusk, and it will be well worth heading out after the sun sets to see them. The bright crescent part of the moon is directly illuminated by sunlight. If the sky is really clear, you should be able to see the dimly illuminated remaining portion of the lunar disc. Its ghostly appearance is caused by sunlight that has bounced off both the earth and the moon before reaching your eyes. Astronomers call this effect earthshine.

This week's chart is drawn for the following night. The 15% illuminated crescent moon, almost four days past new, will be just over 10 degrees above the northwestern horizon. Venus will be below and to the left of the moon, and at 6.30pm will be only five degrees above the treeline.

If you have access to binoculars, or better still a small telescope, be sure to point them at Venus. This week the second planet out from the sun is just under 30% illuminated by the sun, so it, like the moon, is exhibiting a pretty crescent.

On Monday night, the distance between Earth and Venus is a tad over 68,000,000km. Hence, the light you see when looking at the planet began its celestial journey about four minutes before it hits your eyes.