Venus and Moon | 15 July 2018


Mars Retrograde 2018

It has begun. Mars is making the turn from its usual eastward progress across the sky. It will appear to move westward for the next two months. At the end of August it will slowly turn and head eastward again. Why? How can that be?

Mars in retrograde 2018 | Click to embiggen

The answer is simple. Earth orbits closer to the Sun than Mars. We move faster than Mars. We are passing Mars at this time. It is the same perspective as when passing another car. The passed car appears to move backward relative to your faster car.

In addition, Mars grows in size when viewed through telescopes until the end of July. After that, it will decrease in size. If you have access to a telescope, look for Mars in the east after sunset. You’ll need a high power to see any detail. Let’s hope the dust storm settles to reveal those details.

The graphic below from BinTel illustrates the apparent change in diameter given in arc-seconds (“). At the end of July, the Moon will appear about 24″ wide. For reference, the angular diameter of the Sun, or a full moon, is about 1800”, half a degree. That is the width of your little fingernail seen at arm’s length.

BinTel | Andy Casely

Comet Halley | Where Is It Now?

The previous visit by Comet Halley to our part of the inner solar system was in 1986. The time before that was in 1910. The next visit will be in 2061. I have not ruled out seeing it again.

The European Space Agency’s Giotto spacecraft flew within 600 mi (965 km) of Halley and through the tail in March 1986. The dimensions of the comet nucleus were seen as 15×8 km (9×5 mi) and shaped like a potato. Giotto confirmed the existence of organic matter and revealed the surface to be one of the blackest objects in space. Image enhancement was used to brighten the surface to reveal more detail in these fly-by images. Images are from ESA and affiliates.

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Tour of the Moon

Take a time-out from the news of the day or your busy routine. Tour some of the interesting features of our Moon as presented by the NASA Goddard Space Flight Center/David Ladd. Best viewed in HD by using the gear button at the bottom right of the video window.

Mars Passes Saturn | Spring 2018

Earth has been moving closer to Mars this spring as we orbit the Sun. We reach inferior conjunction, our closest to the planet, in late July 2018. Mars will appear larger in telescope views until then. No, it will not appear as large as a full moon contrary to an internet meme that has gone around for years.

Saturn is in the distant backround when viewed early in the mornings. Because Mars is closer to the Sun than Saturn, it passed by the slower moving Saturn. This short animation illustrates the passage. Watch Saturn slowly move across the frame. Also, watch for the Moon to pass by at the end of the animation. That happened on 7 April 2018.

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Supermoon | 31 Jan 2018

In the evening of 30 January, the Moon rose bright and large in the east. Within 12 hours, it would be in the shadow of the Earth. There were a few clouds. The forecast was calling for a 50% cloud cover in the morning.

7 pm CST

At about 3 am I noticed the Moon was shining brightly through the bedroom windows. I felt hopeful the much hyped Supermoon would be visible before moonset/sunrise. I got up at 5:40 and walked down the street a few houses with camera and tripod. The Moon was entering some clouds toward the horizon. Overhead it was very clear. Eclipse was in progress.

We drove to a location away from houses and lights to get one more chance to photograph the beginning of totality. Too late. Clouds took over and the Moon disappeared. We headed home to watch online. NASA carried excellent video from three sites in California. These four images were screen grabs from Griffith Observatory near Los Angeles. They show the blood moon and the emergence from totality.

Using video from NASA via Griffith Observatory, I layered frame grabs onto a disk the size of the umbra of Earth. It shows the relative size of the Moon compared to Earth. Progress was slow as it moved at a speed of about 2,300 mi/hr (3,700 km/hr or 1 km/s). Totality began at 6:51 and ended at 8:08 CST.

Video via NASA | Griffith Observatory

Here is a beautiful time-lapse of the view from Griffith Observatory. It takes only a minute.

As the event ended, the Moon appeared low to the horizon as viewed by a telescope at the Armstrong Flight Research Center at Edwards AFB. These frame grabs captured the distorted Moon behind some hills with wind turbines in view. As the Moon disappeared, it added a sense of finality to the entire event. It was a lot of fun to watch. I hope you were able to see it.