A few days ago, the thin crescent Moon passed close to the planet Venus in the evening twilight sky. Conjunctions such as this repeat at roughly one-month intervals so this is not a rare occurrence—just a beautiful one.
The crescent Moon is ~2.4% illuminated by the direct light of the Sun; the remainder of the Moon is lit by Earthshine which is bright enough to show detail on the shadowed face of the Moon. Leonardo da Vinci explained the phenomenon in the early 16th century when he realized that both Earth and the Moon reflect sunlight at the same time. Light is reflected from Earth to the Moon and back to Earth as earthshine.
As mentioned in the previous post, the planets Venus and Mercury passed very close to each other in the evening twilight sky a few nights ago. In fact, this conjuction is the closest conjunction of these two planets until 2033. I chose to photograph the two planets the night before closest approach as I was interested in getting a bit of separation of the two in both the sky and their reflections in the water.
The first image was taken at 2025 MST 27 May 2021 with an 85mm focal length. The second image was taken a short time later at 2035 MST with a focal length of 120mm.
In the first image, there is a very nice and long reflection of Venus in the water; the reflection of Mercury is also present but is faint and diffuse. In the second image, the planets were just a few minutes away from dropping below the ridge to the northwest. In this image, the reflections of both planets are easily seen.
The weather cooperated nicely with light winds allowing reflections on the smooth water of Upper Lake Mary.
I have had the total lunar eclipse of 26 May 2021 on my calendar for almost a year. So when the date was getting close and the weather forecasts were calling for mostly cloudy skies I was disappointed.
Late in the previous afternoon the high clouds began to move across the southwest. As the day progressed, the clouds became thicker. But it was not a solid mass of clouds; there were some areas of thinner clouds and even a few areas without clouds. So the plan was to be ready to shoot photographs if breaks in the clouds arrived in time.
I had a brief glimpse of the Moon just as the partial eclipse began and then the clouds totally obscured the Moon. We patiently waited for breaks or gaps and hoped to see the Moon during totality. Never happened.
The sky was brightening in the east as twilight arrived. Suddenly, I was able to see the Moon as it dropped close to the horizon where there was a gap in the clouds. For just a few minutes I could see the thin crescent of the lit portion and much of the larger portion that was still in shadow. A few minutes later it dropped below the horizon.
I was pretty happy to snatch this minor victory from what had seemed to be a defeat due to weather!
Next up: the conjunction of the planets Venus and Mercury in the evening sky on 28 May 2021. The forecast looks good.
A few nights ago I shot photographs of the Moon, Venus, and Mercury triplet in the evening sky. After Venus and the Moon set and twilight had ended, I tried something a little different.
I pointed the camera at Sirius, a very bright star, in the southwestern sky. As the light from the star passed through the atmosphere there was obvious “twinkling” of the star. It was this twinkling that I wanted to capture.
To take the photograph, I set an exposure time of 4 seconds and then loosened the ball head on the tripod so the camera was free to move. As I shot the image, I moved the camera up/down, side-to-side, and in circles. The result is a looping trace of the star rather than a pinpoint image.
This image shows the effect of stellar scintillization or twinkling. Twinkling of stars is caused by the passing of light through different layers of a turbulent atmosphere. Most scintillation effects are caused by anomalous atmospheric refraction caused by small-scale fluctuations in air density usually related to temperature gradients. The effects include both variations in luminance (brightness) and in color.
It can be seen from the images that the changes are occurring over very short time periods (on the order of a second or two) resulting in rapid variations in brightness and, especially, color.
This was an amusing way to end an already enjoyable evening of sky watching.
Yesterday (12 May 2021) provided an opportunity to view the thin crescent Moon very close to the planet Venus. Also visible in the evening twilight sky was Mercury higher above the pair.
For a few months each year, it is possible to be located so that the setting of the 1-day old crescent Moon aligns along the length of Upper Lake Mary. This allows for a long fetch of water in which to get reflections of the Moon and planets. Of course, this only works if it is not windy and spring is our windy season. So it was very nice to have both clear skies and very light winds for this event.
In the above image the crescent Moon is just slightly above and to the left of Venus. Near the top center of the image is Mercury. Venus is still rising higher in the sky each day while Mercury is dropping lower. Later this month they will pass by each other with ~0.4° of separation. That should be another interesting event to photograph.