Dawn Sky Delights


Aldebaran About to be Occulted by the Moon

It was one of those mornings when the sky was full of wonder.

After days and nights of smoke from unfortunate fires burning not far away, including in my favourite national park of Waterton Lakes, the sky cleared enough this morning, September 12, to reveal some fine sights.

At 6 a.m. the waning gibbous Moon passed in front of the star Aldebaran in Taurus. It is performing many such occultations of Aldebaran this year, but most aren’t well seen from any one location. This one was ideal, right from my backyard.

The lead image is a “high dynamic range” stack of several exposures showing the waning Moon and star set in some high haze adding the sky colours.

The star winked out behind the Moon’s bright limb as the Moon advanced from right to left (west to east) against the background sky.

Occultation of Aldebaran
Aldebaran nearing the limb of the Moon.
This shows a composite sequence, with images of the star taken every four minutes blended with a single image of the Moon. While it looks like the star is moving, it is really the Moon that is edging closer to Aldebaran.

The star reappeared from behind the dark limb of the Moon, but five minutes after sunrise, with the Moon in a bright blue sky. Still, the star stood out nicely in binoculars and in the telescope for this view.

Aldebaran Near the Moon in Day Sky
Aldebaran off the dark limb of the Moon.
Aldebaran is the point of light at right, just off the invisible edge of the Moon.

I shot stills and video, and compiled them into this short video.

Enlarge it to full screen to view it properly.

Meanwhile, over to the east the twilight sky was awash in planets.

Rocky Planets at Dawn with Labels (Sept. 12, 2017)
The line of dawn planets, with labels.
All the three inner terrestrial worlds were there: Venus, at top, Mercury below Regulus, and Mars lowest of the trio. Of course, a fourth terrestrial world is in the photo, too – Earth!

Mercury was at its greatest western elongation this morning, placing it as far from the Sun and as high in the sky as it gets, with this autumn appearance the best of 2017 for a morning showing for Mercury. Even so, you can see how Mercury is always low and easy to miss. However, this morning it was obvious to the naked eye.

Mars and Mercury will be in close conjunction at dawn on the morning of September 16.

Rocky Planets at Dawn (Sept. 12, 2017)

It was a fine morning to be up early and enjoy the solar system show.

— Alan, September 12, 2017 / © 2017 Alan Dyer / amazingsky.com

 

Comets, Conjunctions, and Occultations, Oh My!


The Moon, Venus and Comet Catalina

What a morning of sky sights, both before dawn and after sunrise.

December 7 – This was the prime day I came to Arizona to enjoy, to be better assured of clear skies. As it turned out this will likely be the cloudiest day of the week here, but skies were clear enough for a fine view of a conjunction and an occultation. The comet was a bonus.

Waning Moon and Venus Rising in Conjunction
This is a stack of 5 exposures: 30, 8, 2, 0.5 and 1/8s, blended with luminosity masks as HDR would not blend images with such a large range of brightness and content, with the shortest exposures having almost no content execept for two bright objects! The camera was on the iOptron Sky-Tracker to follow the sky and keep the sky targets stationary and aligned, thus the blurred foreground. All with the 135mm lens at f/2.8 and Canon 6D at ISO 400.

At 4 a.m. the waning crescent Moon rose accompanied by Venus, as the two worlds appeared in close conjunction in the pre-dawn sky. The view above captures the scene as the Moon and Venus rose over the Peloncillo Mountains of New Mexico. Comet Catalina is in this scene but barely visible.

The Moon, Venus and Comet Catalina
This is a stack of 6 exposures: 30, 8, 2, 0.5, 1/8s and 1/30s, blended with luminosity masks as HDR would not blend images with such a large range of brightness and content, with the shortest exposures having almost no content execept for two bright objects! The camera was on the iOptron Sky-Tracker to follow the sky and keep the sky targets stationary and aligned. All with the 135mm lens at f/2.8 and Canon 6D at ISO 800.

An hour or so later, with the Moon and Venus higher and with skies a little less cloudy, I was able to capture this scene, above, that included Comet Catalina, as a tiny blue dot next to Venus and the Moon. But if I hadn’t labeled it, you wouldn’t know it was there! The comet is proving to be less wonderful than anticipated, and any cloud dims the view even more.

I had hoped for a superb scene of a bright comet next to the two brightest objects in the night sky. But comets do what comets do — surprise people with unexpected brightness (as Comet Lovejoy did last January) or with disappointing dimness … or by disappearing altogether, as Comet ISON did two years ago. I came here in December 2013, to this same location on the Arizona-New Mexico border, to catch ISON but no luck there at all!

Moon & Venus Conjunction at Sunrise (Dec 7, 2015)
This is a stack of 7 exposures from 10 seconds to 0.3 seconds at 1 stop intervals and blended with luminosity masks, to compress the huge range in brightness from the bright Moon and Venus, plus horizon sky, and the darker sky and sunrise clouds. All with the 35mm lens and Canon 6D.

Regardless of the comet, the conjunction of the Moon and Venus was stunning, about as good as such events get. Here’s the view, above, an hour later again, with the eastern sky brightening in the dawn twilight. The only thing that would have made this event even more spectacular is if the Moon had actually covered up Venus in this twilight sky. Not quite.

Daytime Occultation of Venus (Dec 7, 2015)
The occultation of Venus by the waning crescent Moon in the daytime on Monday, December 7 at 9:30 am local time. This is just about 3 minutes before the actual occultation as the advancing Moon is about to cover Venus on the bright limb of the Moon. This is a frame from a 100-frame time lapse. Unfortunately, as I shot this on my trip to Arizona, I did not have more focal length than the 135mm and 1.4x extender used here.

For the occultation itself, we had to wait until well after sunrise for an event in the blue daytime sky, at 9:30 a.m. local time.

All of North America got to see this fairly rare occultation of Venus by the Moon, albeit in the daytime. Nevertheless, the two objects are so bright, this was visible to the unaided eye, even with some cloud about. In binoculars it was wonderful.

To shoot it, all I had was a telephoto lens, so the image scale doesn’t do the event justice. But the image above provides a good impression of the binocular view, with Venus as a brilliant jewel on the “ring” of the Moon.

— Alan, December 7, 2015 / © 2015 Alan Dyer / www.amazingsky.com

Heads Up! – A Comet in the December Dawn


Dec 7 Venus & Moon

A new comet is coming into our morning sky, for our binocular viewing pleasure.

Comet Catalina, aka C/2013 US10, has emerged from behind the Sun and is beginning to rise into our northern hemisphere dawn sky. The new comet promises to be visible in binoculars, but likely won’t be obvious to the unaided eyes.

On the morning of December 7 the comet sits within a binocular field of the waning crescent Moon which itself sits just above brilliant Venus. That in itself will be a remarkable view, best appreciated in binoculars, and a fine photogenic sight for the camera.

The close conjunction of the crescent Moon with Venus alone will be enough of an attraction on December 7, but the comet should add to the scene.

December 7 Venus Occultation

Even more, later in the day the Moon actually passes in front of, or “occults,” Venus in the daytime sky for most of North America.

That occultation happens in the morning for western North America and in the early afternoon for eastern North America. However, you’ll need a telescope to see it well, and very clear blue skies.

Stellarium Occultation

Use planetarium software (the free Stellarium program, for example, shown above, if you do not own astronomy software) to simulate the sky and provide the occultation times for your location. Zoom into the Moon and run time back and forth on December 7 to see when Venus goes behind the Moon and reappears. The screen shot above is for Calgary.

Back to the Comet

Comet Catalina was discovered in October 2013 at the Catalina Observatory in Arizona. The comet spent the last few months in the southern hemisphere sky, but is now coming north and into our sky, but at dawn.

Comet Catalina Path

It rises higher and higher each morning  through December and into the new year. It may remain at fifth magnitude, bright enough to be easily visible in binoculars from a dark site, but likely not naked eye.

The chart above plots the comet at daily intervals, from December 4 to January 1. The comet is shown for December 15. Note that on the morning of January 1 it sits within a telescope field of the bright star Arcturus.

The distance from Earth to the comet decreases through December and early January, keeping the comet at a constant brightness even as it recedes from the Sun. We are closest to Catalina on January 17, at a far distance of 108 million km. But in late January the comet fades rapidly to become a telescope target.

To see Comet Catalina this month, get up 1 to 2 hours before sunrise and look southeast to east. But you will need dark skies to see it well. This will not be a good urban comet.

Nevertheless, as far as we know, this will be the best comet of 2016.

— Alan, December 2, 2015 / © 2015 Alan Dyer / www.amazingsky.com

 

A Stellar Occultation by the Moon


Impending Occultation of Beta Capricorni

The double star Beta Capricorni disappears in a wink behind the Earthlit edge of the Moon.

The evening of Wednesday, November 26 provided a bonus celestial event, the eclipse of a double star by the Moon.

The star is Beta Capricorni, also known as Dabih. I had a ringside seat Wednesday night as the waxing Moon hid the star in what’s called an occultation.

Dabih is a wide double star, composed of a bright magnitude 3 main star, Beta1 Capricorni, and a fainter magnitude 6 companion, Beta 2 Capricorni. You can see both in the still image view at top. Their wide separation makes them easy to split in binoculars.

In reality, they are separated in space by an enormous gap of 21,000 times the distance from the Earth to the Sun. By comparison, distant Pluto lies an average of just 40 times the Earth-Sun distance.

With such a wide separation Beta1 and Beta2 take an estimated 700,000 years to orbit each other.

Beta1 is a giant orange star 600 times more luminous than our own Sun and 35 times bigger. Beta2 is a blue subgiant 40 times more luminous that the Sun.

Adding to the complexity of the system, Beta2 is also a close double, while Beta1 is a tight triple star, making for a quintuple star system.

The movie below records each occultation, first of the fainter blue Beta2 star, then of the brighter Beta1 star.

Each occultation happens in an instant to the eye. However, stepping through the video shows that the brighter star took 4 video frames to dim, about 1/10th of a second. Whether this is real, due to the star’s giant size, or just an effect of the twinkling of the atmosphere, is questionable.

Technical notes:

The still photo is a “high dynamic range” stack of 12 exposures from 4 seconds to 1/500th second, taken with the Canon 60Da camera at ISO 400, to capture the huge range in brightness, from the dark side of the Moon and stars, to the bright sunlit crescent. I used Photoshop’s HDR Pro module to stack the images and Adobe Camera Raw in 32-bit mode to do the tone-mapping, the process that compresses the brightness range into a final image.

I shot the video with the 60Da camera as well, setting it to ISO 6400, and using its video mode to record real-time video clips, both in HD 1920×1080 for the wide-field “establishing shots,” and in its unique 640×480 Movie Crop mode for the close-ups of the actual occultations. Those two clips appear as inset movies. I edited and processed the clips, plus added the titles, using Photoshop and its video capabilities.

All were shot from New Mexico with the TMB 92mm refractor at f/5.5.

– Alan, November 28, 2014 / © 2014 Alan Dyer

Venus Disappears


 

On the afternoon of Monday, August 13 the waning crescent Moon slid in front of Venus in broad daylight. This sequence captures the disappearance.

It was touch and go getting this as high cloud kept moving through. A few minutes earlier the Moon and Venus were in clear blue sky, but at the time of the occultation, haze whitened the sky and cut down the  contrast on an event that takes a telescope to see well. When the sky was clear it was easy to sight the Moon with unaided eyes and therefore focus your eyes on infinity. Venus next to the Moon popped into view, even naked eye. It was a rare chance to easily sight Venus in the daytime. But as it got close to the Moon Venus became harder to see naked eye, and the haze then made it impossible. But through a telescope it was just the opposite — Venus’s bright disk stood out even when the Moon was washed out and invisible.

For southern Alberta the occultation took place at 2:11 pm MDT. I missed seeing it emerge from behind the Moon. I was already inside processing this image.

It has been quite a year for Venus. It’s not over yet, as Venus continues its morning show and has close encounters with the Moon and the star Regulus this autumn.

— Alan, August 14, 2012 / © 2012 Alan Dyer