Can you spot the phase of Venus with the naked eye over the month of January?
Venus wasn’t the easiest planet to spot in 2021. Loitering in the evening sky after sunset, its altitude has been low. It is visible in the evening sky before inferior conjunction on 9 January 2022, after which it re-emerges in the morning sky. Venus is the brightest of the planets, regularly appearing brighter than mag. –4. It also has the largest potential apparent size, something which is only achieved close to inferior conjunction. The challenge is to see whether you can spot the planet’s phase with your eyes only.
When Venus is close to inferior conjunction, it appears through the eyepiece as an ultra-thin crescent. It also approaches the theoretical limit of nakedeye resolution, at 1 arcminute; it will appear larger than 1 arcminute between 1-17 January and it’s not uncommon to ‘see’ the phase of Venus when staring at it. Unfortunately, this often turns out to be down to visual errors in your eye’s optical path rather than a true phase. Don’t worry, Venus is tricky in this respect!
A common issue when viewing a bright point source of light is the presence of astigmatic rays that emanate from the point, which can produce the appearance of a crescent shape. If you see a clear shape to the planet, tilt your head. If the shape appears to rotate, it is in your head.
Part of this challenge will be to locate Venus itself. As it is close to the Sun, make sure you observe safely, and only when the Sun is below the horizon. Consider enlisting help from someone who (a) you know has good eyesight, and (b) knows little about astronomy or Venus.
Don’t prompt them with any information, just ask them to look hard at the planet and write down what they see. If they can see a shape to the planet, ask them to draw its orientation relative to the horizon.
Another thing to try is to use a large sheet of card with a hole, placed some distance from you. Looking at Venus through the hole without the distraction of its surroundings may help. Remember,
This is a scientific experiment and as such you may report a negative result, which is fine. If you experience a positive result, we’d love to hear from you, along with the date, time and details of any method used. Enjoy the challenge!
