Skywatch Line for Wednesday and Thursday, June 5 and 6, 2024, written by Alan French
This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, June 5 and 6, 2024, written by Alan French.
The Sun rises at 5:18 A.M. on Wednesday and sets at 8:30 P.M. On Thursday it rises at 5:17 and sets at 8:31. This Thursday has just 8 minutes more daylight than last Thursday. In May we gained just under 1 hour, 2 minutes of daylight. As the Sun approaches the Summer Solstice on June 20, the rate of increase in daylight has been decreasing. After the Solstice, we begin losing daylight, although slowly at first.
The Moon reached last quarter last Thursday and will reach new Thursday morning. Aside from a chance to spot a very old Moon in the morning sky on Wednesday, the sky will be dark and moonless.
To spot the Moon before sunrise Wednesday morning, you will need a good, unobstructed view of the east northeastern horizon free of clouds. Binoculars will improve your chance of success. To catch the slender Moon before twilight seriously interferes, start looking around 4:30 A.M. The Moon will be just under 2 ½ degrees above the horizon. By 4:40 A.M. the Moon will be just under 4 degrees high and at 4:50 almost 5 ½ degrees high. By then morning twilight will be a serious problem and hamper your efforts. (To estimate sky distances, the tips of the first three fingers, held together at arm’s length, span 5 degrees.)
On Thursday the Moon will reach new and be too close to the Sun to observe. These are good nights to enjoy the night sky away from city lights. Unfortunately, this close to the Summer Solstice with the Sun near its farthest north, and the clocks having sprung ahead for Daylight Saving Time, the last vestiges of evening twilight do not vanish until 10:45 P.M. EDT under dark skies.
If you are where you can enjoy dark skies, free of light pollution, give your eyes time to adjust to the dark. Full dark adaptation takes 30 to 40 minutes, although 20 minutes will get you much of the way there. It is also a faster process if you have avoided bright lights for a while before hand. Coming from a dim environment, dark adaption can take 20 minutes. Coming from a bright environment, it may take an hour to complete.
There are two steps to dark adaptation. First, our pupisl open wider to let in more light. This is a minor improvement but happens quickly. Generally, the pupils of younger people open wider, but there is a lot of variation. There is also a chemical change in the retina, greatly increasing the eye’s sensitivity to light. Exposure to light will reverse the change, so amateur astronomers generally use dim red lights to look at star charts and preserve their dark adaptation. Likewise, screens on phones and tablets should be as dim as possible to protect night vision and allow the best views of the night sky. Red gels are available to make them even dimmer than settings allow.