The Waxing Moon of Spring


 

Four-Day-Old Moon with EarthshineSpring is the season for Earthshine on the waxing Moon.

April 8 was the perfect night for capturing the waxing crescent Moon illuminated both by the Sun and by the Earth.

The phase was a 4-day-old Moon, old enough to be high in the sky, but young enough – i.e. a thin enough crescent – that its bright side didn’t wash out the dark side!

In the lead photo at top, and even in the single-exposure image below taken earlier in a brighter sky, you can see the night side of the Moon faintly glowing a deep blue, and brighter than the background twilight sky.

Four-Day-Old Moon in Blue Twilight
The 4-day-old waxing crescent Moon on April 8, 2019 in a single exposure when the Moon was still in the bright blue twilight. Even so, the faint Earthshine is just becoming visible. This is with the 105mm Traveler refractor and 2X AP Barlow lens for an effective focal length of 1200mm at f/12, and with the cropped-frame Canon 60Da at ISO 400, in a single 1/8-second exposure.

This, too, is from sunlight, but light that has bounced off the Earth first to then light up the night side of the Moon.

If you were standing on the lunar surface on the night side, the Sun would be below the horizon but your sky would contain a brilliant blue and almost Full Earth lighting your night, much as the Moon lights our Earthly nights. However, Earth is some 80 times brighter in the Moon’s sky than even the Full Moon is in our sky.

Four-Day-Old Moon with Earthshine
The 4-day-old waxing crescent Moon on April 8, 2019 in a blend of short and long exposures to bring out the faint Earthshine on the dark side of the Moon and deep blue twilight sky while retaining details in the bright sunlit crescent. This is with the 105mm Traveler refractor and 2X AP Barlow lens for an effective focal length of 1200mm at f/12, and with the cropped-frame Canon 60Da at ISO 400, in a blend of 7 exposures from 1/30 second to 2 seconds, blended with luminosity masks from ADP Pro3 extension panel in Photoshop.

 

Unlike the single image, the lead image, repeated just above, is a multi-exposure blend (using luminosity masks), to bring out the faint Earthshine and deep blue sky, while retaining details in the bright crescent.

Once the sky gets dark enough to see Earthshine well, no single exposure can record the full range in brightness on both the day and night sides of the Moon.

 

Waxing Moon, Mars and the Taurus Clusters
The 4-day-old waxing crescent Moon on April 8, 2019 with it below Mars (at top) and the star clusters, the Hyades (at left, with reddish Aldebaran) and Pleiades (at right) in Taurus, and set into the deep blue evening twilight. This is with the 135mm Canon telephoto at f/2.8 with the Canon 6D at ISO 400, in a blend of 7 exposures from 1/4 second to 8 seconds, blended with luminosity masks from ADP Pro3 extension panel in Photoshop, to prevent the Moon from being too overexposed while retaining the stars and blue sky. The camera was tracking the sky.

April 8 was a great night for lunar fans as the crescent Moon also appeared between the two bright star clusters in Taurus, the Hyades and Pleiades, and below reddish Mars.

It was a fine gathering of celestial sights, captured above with a telephoto lens.

April 8 Sky

This show the chart I used to plan the framing, created with StarryNight™ software and showing the field of the 135mm lens I used.

The chart also shows why spring is best for the waxing Moon. It is at this time of year that the ecliptic – the green line – swings highest into the evening sky, taking the Moon with it, placing it high in the west above obscuring haze.

That makes it easier to see and shoot the subtle Earthshine. And to see sharp details on the Moon.

After the sky got darker I shot the crescent Moon in a short exposure to capture just the bright crescent, included above in two versions – plain and with labels attached marking the major features visible on a 4-day Moon.

If you missed “Earthshine night” this month, mark May 7 and 8 on your calendar for next month’s opportunities.

Clear skies!

— Alan, April 9, 2019 / © 2019 Alan Dyer / AmazingSky.com 

 

The Ghostly Glow of Gegenschein


Northern Spring Sky Panorama

It takes a dark spring night to see it well, but now lurking near Jupiter is a ghostly sky glow called Gegenschein. 

This diffuse glow lies directly opposite the Sun. It is caused by sunlight reflecting off interplanetary dust particles in the outer solar system. They reflect light more effectively at the anti-Sun point where each dust particle is fully lit by the Sun.

Like the Sun, the Gegenschein moves around the sky along the ecliptic, moving about a degree from west to east from night to night. March and April provide good nights for seeing the Gegenschein as it then lies in an area of sky far from the Milky Way.

Even so, it is very subtle to the unaided eye. Look south at about 1 a.m. local daylight time.

However, this year, in early April the Gegenschein will be more difficult as it will then lie right on top of Jupiter, as that planet reaches its point opposite the Sun on April 7. Jupiter will then be superimposed on the Gegenschein.

The main image at top is a 7-image vertical panorama of the spring sky, from Corvus and Virgo above the horizon, up past Leo, into Ursa Major and the Big Dipper overhead. Spica lies below bright Jupiter, Arcturus in Böotes is at left, while Regulus in Leo is at right. The grouping of stars near centre is the Coma Berenices star cluster.

Orion over the Old Barn

Earlier in the night, I shot the sky’s other main glow – the Milky Way, as the winter portion of the Milky Way around Orion set into the southwest.

But over in the west, at the right edge of the frame, is the Zodiacal Light, caused by the same dust particles that create the Gegenschein, but that are located in the inner solar system between us and the Sun.

The Zodiacal Light is better depicted in images in my previous post from Dinosaur Park

We bid adieu to the winter Milky Way now. As it departs we are left with an evening sky without the Milky Way visible at all. As seen from northern latitudes it lies along the horizon.

But later in spring, late at night, we’ll see the summer Milky Way rising, beginning its seasons of prominence until late autumn.

— Alan, March 19, 2017 / © 2017 Alan Dyer / AmazingSky.com 

 

A Panorama of the Spring and Winter Sky


Winter and Spring Sky Panorama

I present a sweeping panorama of the winter and spring stars on a February night. 

The lead image is a panorama I shot last Saturday, February 27 that takes in about 200° of sky from northeast to west, and nearly to the zenith. It encompasses most of the northern spring and winter stars and constellations.

I’ve added the labels to help you pick out the celestial highlights. The winter sky, containing Orion as the central constellation, is at right setting into the west. This area of sky contains a rich collection of bright stars and identifiable constellations.

The left side of the sky contains the spring constellations, now coming into view in the east. Note how that area of sky is sparsely populated by bright stars. You can see the Big Dipper, Regulus in Leo, and Arcturus rising at lower left.

The reason for the difference is the Milky Way – you can see it at right arcing up from the southern horizon passing by Orion and through Gemini, Taurus and Auriga. In that direction we are looking into the outlying spirals arms of our galaxy, toward rich areas of star formation.

To the east, at left, we are looking at right angles out of the plane of our spiral galaxy, toward the galactic North Pole, here just left of Leo. In that direction there are very few bright stars between us and the starless depths of intergalactic space. The spring sky is rather blank compared to the rich winter sky.

But you can see Jupiter, the brightest object in view here, and now prominent in the evening sky.

Note one other subtle glow just above Jupiter. That diffuse glow is the Gegenschein, caused by sunlight reflecting off interplanetary dust opposite the Sun in our solar system and in the plane of the ecliptic.

Jupiter is just east (left) of the Gegenschein here, as Jupiter was then just over a week before its date of opposition, March 8. By then the Gegenschein will have moved to superimpose right over Jupiter, as both then lie opposite the Sun.

Winter and Spring Sky Panorama

I shot this scene from home on February 27, 2016, using the new iOptron iPano motorized “gigapan” unit, which I programmed to move and shoot 36 exposures with the Canon 5D MkII and 35mm lens, arranged in 4 rows high with 9 panels wide in each row from east to west. The result is a huge mosaic, 24,000 by 10,000 pixels.

Each exposure was 25 seconds at f/2 and at ISO 3200. The camera was not tracking the sky. I stitched the 36 segments with PTGui using its Spherical Fisheye projection. The image has black margins but I think the circular format is more suggestive of the spherical dome of the sky above and around you. But that’s me, a longtime planetarium show producer.

Next time I will shoot the zenith cap images as well!

— Alan, February 29, 2016 / © 2016 Alan Dyer / www.amazingsky.com

 

Heads Up! – Mercury Rising


May 6 Mercury

The next two weeks are the best in 2015 for sighting Mercury in the evening sky.

Mercury is coming into view in our evening sky, climbing as high as it can get for us in the Northern Hemisphere. This is our best chance for us to sight Mercury as an evening star in 2015.

Spring is always the best time to catch elusive Mercury. The angle of the ecliptic – the path of the planets – swings up highest above the horizon in spring, putting Mercury as high into the evening twilight as it can get. This makes it easier to sight Mercury than at other times of the year when, particularly for observers at northern latitudes, Mercury can be lost in the twilight glow and horizon haze.

When it is at its highest Mercury is surprisingly bright, appearing as a bright star easily visible to the naked eye. However, locating it at first in the twilight usually requires a scan with binoculars.

Mercury will be at its highest on May 6 when it reaches “greatest elongation.” However, it will be almost as good for a week on either side of that date.

So set aside a clear evening during the first two weeks of May to search for the inner planet. (The green line is Mercury’s path relative to the horizon with the green dots marking its position at daily intervals.)

Mercury will be shining above fainter Mars, and well below brilliant Venus, now dominating our evening spring sky. Look north of due west during the hour after sunset.

Mercury & Venus Conjunction Closeup (Jan. 10, 2015)
Mercury and Venus on January 10, 2015 from New Mexico.

This view captures Mercury at its last good evening appearance, back in early January when it appeared close to Venus, then emerging into the evening sky. You can compare their relative brightness.

By coincidence, the emergence of Mercury into our evening sky comes just as it loses its lone visitor from Earth. Since 2011, NASA’s Messenger probe has been orbiting and mapping Mercury.

On April 29, with the probe exhausted of its maneuvering fuel, Messenger is scheduled to end its mission by crashing onto the planet, adding a new crater to Mercury’s barren and volcanic surface.

A global false-color map of the mineral composition of Mercury from Messenger data.
A global false-color map of the mineral composition of Mercury from Messenger data.

This is a recent map of Mercury from Messenger. For more details, see the mission’s website.

– Alan, April 30, 2015 / © 2015 Alan Dyer / www.amazingsky.com

Milky Way and the Northern Lights


Aurora and the Milky Way (May 6, 2013)

The Milky Way appears from behind the colourful curtains of the Northern Lights.

This was the scene last Saturday night, into the pre-dawn hours of Sunday morning, May 5, as the summer Milky Way rose in the east while a display of aurora  played across the northern sky. The Northern Lights weren’t particularly bright this night, but the long 2-minute exposure I used to bring out the Milly Way recorded the aurora with colours and an intensity only the camera could see this night.

The green is from oxygen glowing in the lower part of the atmosphere, though still some 80 km up, where only rockets and high-altitude balloons can fly. The tops of the auroral curtains are tinged with the pinks from another type of oxygen emission possible only at the very top of our atmosphere, where molecules are few and far between and what’s left of the air that surrounds us meets the vacuum of space some 150 km up.

From Earth it’s hard to visualize just what we are seeing when we look at display like this. But check out some of the Aurora videos at  NASA’s Gateway to Astronaut Photography of Earth. You’ll see time-lapse videos taken from the Space Station as it flies by and through the same types of aurorae with green lower bands and pink upper fringes, beautifully captured  floating high above the Earth in vertical curtains reaching up into the blackness of space.

– Alan, May 8, 2013 / © 2013 Alan Dyer