Lunar Occultation of Venus
April 7, 2024

 

Update, April 7, 2024: In a nutshell, my effort to observe this occultation was thwarted by clouds. About ten minutes before the predicted first contact (Venus ingress), I started searching for Venus with my 88 mm spotting scope at 25x. I first centered on the Sun by minimizing the scope's shadow on my shirt, then putting it dead center by looking for the disc of sunlight on the eyepiece lens, viewing from the side, not directly into it. From there, I dropped about 9° and shifted right about 12° using the angular scale on my gimbal head to shift to the expected position of Venus (these spans were generated by SkyTools). Unfortunately, the graduations on the head were in fairly wide 7.5° increments, and even worse, the sky was more cloudy than clear. There were many cumulus clouds passing by with smaller patches of nice blue sky appearing sporadically between the clouds. Those clear patches were just too few and far between for me to locate Venus. Not surprisingly, I didn't see the thin crescent Moon either. The cloud situation was no better around 1:48 pm for third contact (the beginning of Venus egress), so I didn't even try.

The graphic above is a screen capture from SkySafari 7 on my iPad. It shows the Moon as it starts to occult Venus on April 7, 2024, at 12:37:42 pm EDT. In this wide-field view, the symbols for Venus and the Moon overlap, so there's a close-up screen clip below. Of course, if the weather cooperates, the sky will be a bright blue color, but for these charts, sunlight was turned off to reveal the full sky. At the time, Venus will be 15.3° from the Sun, 10.2″ apparent diameter, 97% illuminated and magnitude -3.9. The Moon will be a thin crescent, 1.8% illuminated, one day before New Moon and the Total Solar Eclipse (just a partial eclipse here in New Jersey). Here's the IOTA page for this occultation, including a map showing where the occultation will be visible (including areas in the path of totality on April 8), and time predictions for various cities. There's also a brief story about this occultation in the April 2024 issue of Sky & Telescope magazine, at the bottom of page 50.

 

Here's a close up view of the thin crescent Moon making first contact with Venus at 12:37:42 pm EDT on April 7, 2024, for a location of 40°N-75°W. The lunar limb will be moving largely upwards with respect to Venus as it covers it. In my experience, SkySafari times for lunar occultations have been pretty accurate in the past, but one should allow a good margin of error and look much sooner, especially since it may difficult to find them in midday. On the positive side, I have spotted Venus in the daytime on many occasions (with optical aid, binoculars or a small scope), but be careful to avoid the nearby sun. The thin lunar crescent probably won't be visible, even with optical aid, but if Venus is found, one should see it being covered over the course of 26 seconds or so, as opposed to stellar occultations, which are usually instantaneous. Venus will reappear about 1:48 pm, but it may be difficult to find/see without a tracking mount as it will emerge from the unilluminated limb of the Moon, in what will otherwise look like blank sky.

Joe Stieber
SJAstro.org Home Page