Looking eastward the morning of April 19th with a 5 degree FOV. (Created by the Author in Starry Night).
Where have all the planets gone? Well, with the exception of Saturn, they’ve all been hiding in the direction of the Sun. That’s all beginning to change this week, however, as Mars, Mercury, and Jupiter slip into the dawn sky to join Venus in what will turn into a splendid early morning multi-planet conjunction in early May. A planetary conjunction sampler starts this week, with a close pairing of Mars and Mercury in the dawn skies. At closest separation the morning of the 19th, the two will be only 0.7° degrees apart, one of the best planetary pairings of the year. Use the brilliant Venus, still high in the sky to find the elusive pairing; at sunrise, the two will still be less than 10° degrees above the horizon. Mercury will be the easier of the two to spot with binocs, and the pair will fit nicely into a wide telescopic view.
But there’s another reason to set that AM alarm; the Lyrid meteors, the first good shower of the springtime season, peaks on the morning of Friday, April 22nd. Expect a zenithal hourly rate of around 20 meteors per hour radiating from high in the northern hemisphere sky in the constellation Lyra.
The astro-term this week is Troxler’s Effect. This rather trippy illusion is created when the human eye fixates on a particular point causing peripheral stimulation in the field to fade, change color, or disappear. Our eyes have only a sharp field of view directly at the center of the fovea about the angular size of a Full Moon; as you read this, you are shuffling that sharp field back and forth, and we tend to scan the heavens in a similar fashion when we look at the night sky. Troxler’s Effect comes into play during observational astronomy when trying to spot a faint meteor or difficult conjunction pairing in that our eyes have a tough time catching a low contrast source against a brightening sky background. Blame our eyes, that often defective optical instrument made of water and jelly!