Gaze into the Heavens

My Sky Blog – Page 1



Asteroid Florence’s Close Approach to Earth – September 2017


On September 1, 2017, a large near-Earth asteroid named Florence (its full name is 3122 Florence, or 1981 ET3) made a safe but relatively close approach to Earth, coming to within 4.4 million miles. That’s approximately 18 times the distance from the Earth to the Moon. At its maximum apparent brightness when observed from Earth, it reached 9th magnitude, which is almost as bright as the planet Neptune. NASA’s website says this was the closest approach by this asteroid since 1890 and the closest it will come to Earth until after 2500. This quote on NASA’s website from Paul Chodas, who is manager of NASA’s Center for Near-Earth Object Studies (CNEOS) at the Jet Propulsion Laboratory in Pasadena, puts this close approach in perspective. “Florence is the largest asteroid to pass by our planet this close since the NASA program to detect and track near-Earth asteroids began.” Florence was first discovered in 1981, and scientists have been tracking it carefully ever since. At 2.7 miles wide, it’s a little less than half the estimated size of the asteroid that wiped out the dinosaurs 65 million years ago.

I was traveling during the close approach and could not observe or image the asteroid, but above is a video I later created from some still images my dad took from our family observatory in Tennessee. It shows Florence moving through the field of view in the constellation Delphinus the dolphin over a period of approximately 35 minutes in the early morning hours of September 3. The original images were 10 second exposures taken at intervals through a monchromatic (black and white) Atik 314L+ CCD camera and a TEC 200mm f/8 fluorite apochromatic refractor at prime focus. I created the MP4 video from 180 still images that were stored in TIFF format. Interestingly, there are at least three other fainter objects moving through the video at various points. After some follow-up sleuthing, I’ve concluded that these objects are man-made satellites. I used “Visual PinPoint” software made by a company called DC-3 Dreams to determine the coordinates of the stars in my Florence movie — a process called “plate solving.” Then, I used JPL’s small body identification tool on its “Solar System Dynamics” web page that can be found here: [link to JPL small body identification page]. According to the JPL database, other than 3122 Florence, there were no asteroids or comets visible in those positions at 2:11 a.m. CDT on September 3, when the image I used for this process was captured.

Here is a combined series of the same 180 images showing the path of Florence across the field of view. The asteroid seems to vary slightly in brightness at several intervals along its track in this image. This could be the result of atmospheric interference, but it could also result from areas of non-uniform reflectivity on the asteroid’s surface that are visible at various times during its 2.3 hour rotational period.

Additional information about Florence, including videos illustrating its orbital path during its recent close approach and the announcement that the asteroid has two small moons, can be found on NASA’s website here: [link to NASA web page on Florence] and on the CNEOS/JPL website here: [link to CNEOS announcement of Florence’s moons].



The Great North American Eclipse of 2017 – August 21, 2017


For many months, we’ve been planning carefully for the August 21 total solar eclipse that brought totality right to my hometown of Nashville. Yesterday, the big day finally arrived! I’m in my second year at Georgia Tech, where I’m studying aerospace engineering. Our first day of classes for our fall semester was yesterday — the same day as the eclipse. Unfortunately, Atlanta was well outside the path of “totality,” which is the roughly 70 mile wide swath across the continental U.S. where the Moon would fully obscure the disk of the Sun. So staying at school was not an option if I wanted to experience a total eclipse firsthand, and I decided months ago that I would make the trip back home for eclipse day. About a week beforehand, we decided to observe it with some friends at their farm outside Lebanon, Tennessee. Lebanon is near the “centerline” of the Moon’s shadow for this particular eclipse, which meant the “total” phase of the eclipse would last a full 2 minutes and 30 seconds there. (Both our observatory and my childhood home were south of the path of totality, so observing totality from those locations wasn’t an option.)

We arrived at our observing site around 10:30 a.m. to begin setting up. We used much of the same equipment we’ve previously used for our wide-angle Milky Way photos – a Canon 6D DLSR camera mounted on an iOptron SkyTracker Pro equatorial head, and a Manfrotto tripod. This time, we used a newer version of the SkyTracker that has an option for setting the tracking rate to match the apparent motion of the Sun in the sky. The lens we chose was a Canon EF 100-400mm f/4.5-5.6L IS US zoom. During the partial phases of the eclipse, we used two different solar filters placed over the front of the camera lens to safely center and image the sun — a glass solar filter made by Thousand Oaks Optical that gave the Sun a warm, orange tone, and a Kendrick Solar Filter that uses Baader Solar Film and that gave the Sun a white tone. During totality, we removed the filters and imaged the Sun directly through the camera lens, and we locked the focal length of the lens at 400mm and set the ISO and aperture settings on the camera to 200 and f/8, respectively. Only the exposure lengths varied from shot to shot. Because we wanted to soak in the eclipse experience and not have to spend all our time fiddling with the camera, we brought along a laptop computer loaded with a software program called “Eclipse Orchestrator,” which is made by Moonglow Technologies. It allowed us to control the camera remotely and program in a sequence of photographs during both the partial phases of the eclipse and totality at a variety of exposure lengths that were optimized for what we wanted to image. In choosing the exposure lengths, we relied on guidance from accomplished eclipse photographer Fred Espenak that can be found on his website here: [link to the “Mr. Eclipse” website].

While there were clear skies to the south of us, a single, lazy cluster of cumulus clouds hung over our observing site and gave us only intermittent views of the Sun from the beginning of the partial eclipse around noon local time right up to the beginning of totality around 1:28 p.m. Central time. As totality began, the sky darkened quickly to a deep twilight – peach near the horizon and dark purple-gray overhead – and temperatures dropped noticeably. The goats in the pasture nearby began to bleat. All very fascinating things to witness, but the eclipsed Sun was still behind those stubborn clouds. Then, just when our shot at seeing the fully eclipsed Sun seemed lost, about 15 seconds into totality, the clouds seemed to dissolve, and we had a spectacular view of the totally eclipsed Sun! Below are some of the photos our autocapture routine in Eclipse Orchestrator captured while we were taking things in with our eyes. Note that all of these are unprocessed images, except for the image showing the “diamond ring effect,” as noted in its caption.

Above is an image we took of the fully eclipsed Sun, with two red “prominences” and the whitish inner corona of the Sun visible above the dark limb of the Moon. Exposure of 1/2000 of a second at f/8, ISO 100.

Another image of the fully eclipsed Sun through wispy clouds showing more of the corona. Exposure of 1/2000th of a second at f/8, ISO 200.

The image above captured the “Baily’s Beads,” which are pearl-like beads of light from the Sun’s disk that shine though low gaps in the hills on the limb of the Moon and look like a necklace. Exposure of 1/4000th of a second at f/8, ISO 200.

Above is a photo that’s been processed in Adobe Photoshop showing the beginning of the “diamond ring effect” just as the total eclipse was ending. The burst of light from the Sun’s disk past the lunar limb just as the eclipse ends gives the impression of a brilliant diamond atop a ring. This shot also shows the clouds we were contending with during totality. Exposure of 1/100th of a second at f/8, ISO 200.

Finally, above is a photo of the partially eclipsed sun about an hour after totality ended through a Thousand Oaks solar filter (exposure of 1/1000th of a second at f/8, ISO 200), followed by a similar shot taken a few moments later through a Kendrick solar filter for comparison (exposure of 1/1250th of a second at f/8, ISO 100). In both images, dark sunspots are visible on the Sun’s disk. Sunspots are areas of the Sun’s outer photosphere that are slightly cooler (between 2,700° and 4,200° Celsius) than the surrounding areas (which average around 5,500° Celsius).

What a fantastic experience! I’m so glad I got to experience it with family! If you’re in North America but weren’t able to see the 2017 eclipse, it’s not too early to begin planning for the next big total eclipse here, which will be on April 8, 2024. The path of the 2024 eclipse can be viewed in Google Earth using a downloadable overlay from this terrific website by Xavier Jubier, which we used to plan our viewing for yesterday’s eclipse: [link to Jubier website].



My Presentation on the morning of the total eclipse at my high school alma mater, St. Cecilia Academy in Nashville – August 21, 2017


I was honored to receive an invitation to speak at my alma mater, St. Cecilia Academy in Nashville, on the morning of the total solar eclipse. I spoke to the student body for about 15 minutes about eclipses generally, including the differences between solar and lunar eclipses, and what they could expect to see during the partial and total phases of the August 21 eclipse. There was also a detailed presentation about how to view the eclipse safely. St. Cecilia distributed eclipse glasses to all its faculty and students, and later that day, everyone was allowed to go outside to witness totality. Go SCA scarabs!



Night Vision Observing and Photography with a Canon 100-400mm Zoom Lens – July 2017


This summer, I’ve been taking classes at Georgia Tech and continuing work on a satellite project. During weekends when I’ve been home, I’ve continued doing some experimenting on ways to achieve a broad range of magnifications and fields of view with our NVD Micro night vision monocular that’s equipped with an L-3 night vision image intensifier. In July, we fitted a Canon EF 100-400mm f/4.5-5.6L IS US zoom lens to the monocular and inserted a filter holder that allows us to insert 36mm filters into the light path, including an Astronomik 12nm hydrogen-alpha filter, a Baader 7nm hydrogen-alpha filter, and a Baader 610nm long pass filter. Although DLSR photos don’t fully convey the wonderful visual experience of stargazing with this setup, they’re a useful approximation. The image below is a 5 second unguided exposure taken with our Canon 6D DLSR, which has been modified to make it more sensitive to hydrogen-alpha wavelengths. It shows both the Trifid Nebula and the Lagoon Nebula in the same field of view with plenty of room to spare. This view was achieved with our Canon 100-400 zoom lens and the Astronomik 12nm hydrogen-alpha filter. The zoom lens allows us to dial in the exact magnification needed to frame each specific object.



Now It’s Saturn’s Turn! Images from the Cassini Mission’s Grand Finale – April 26, 2017


After 13 successful years studying Saturn, the historic Cassini-Huygens mission is drawing to a close. Cassini-Huygens is a joint project of NASA, the European Space Agency (ESA), and the Italian space agency (ASI). For more than a decade, it has provided us with our closest look ever at Saturn and its rings and moons. With the fuel it requires for orbital corrections now running low, the Cassini spacecraft will made a scheduled, controlled dive into Saturn’s atmosphere and burn up on September 15, 2017. This is intended to ensure that no biological contaminants from the spacecraft wind up on any of the moons of Saturn that could potentially support life.

In the meantime, the folks at NASA’s Jet Propulsion Laboratory (JPL) at Caltech in Pasadena, California, have a few more orbital engineering tricks up their sleeves. Beginning last December, Cassini’s orbits have been adjusted to give us an even closer view of the giant planet’s rings and upper atmosphere. On April 26, Saturn made its first of 22 dives through the space between Saturn’s rings and the planet’s upper atmosphere. Here are some of the images it has recently returned:

Planet Earth is visible through a gap in Saturn’s rings as the tiny white dot in the middle of the first image above, which Cassini took on April 12, 2017. The second image above of a storm in Saturn’s upper atmosphere was taken by Cassini as it passed between the planet and its rings on April 26, 2017. Both images courtesy of NASA/JPL-Caltech/Space Science Institute.

More information about the “Grand Finale” phase of the Cassini mission, including diagrams and animations of Cassini’s orbits, can be found on the JPL website here: [link to Cassini mission “Grand Finle” page on JPL website].



More Amazing Jupiter Images from NASA’s Juno Mission – March 1, 2017


The Juno spacecraft keeps returning gorgeous images of Jupiter. On March 1, NASA released this high resolution of an area of Jupiter’s South Equatorial Belt near the famous Great Red Spot. Juno captured this image during a flyby back on December 11 that brought the craft to within 5,400 miles of Jupiter’s cloudtops.




Several Respected Scientists Are Advocating that Pluto Should Be Classified as a Planet Again – February 22, 2017


As of this writing, NASA’s website states that Pluto is a “dwarf planet,” and this is consistent with the rather controversial definition of a planet that the International Astronomical Union (IAU) announced in 2006. Dr. Alan Stern of NASA, who is the Principal Investigator for the agency’s recent New Horizons flyby mission to Pluto, is one of a significant number of vocal critics of the 2006 “demotion” of Pluto from the ranks of the the Sun’s major planets — a status it had held since its discovery in the 1930s. Several mainstream media outlets reported this month that Dr. Stern and four others have sent a proposal to the IAU advocating the adoption of a new definition of the term “planet” that focuses on the intrinsic geophysical characteristics of celestial bodies rather than their extrinsic orbital characteristics. The definition of “planet” that Dr. Stern’s group is proposing is worded as follows:

“A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters.”

This is likely to be controversial, however, as under this proposed definition, at least 110 currently known objects in our solar system alone would be classified as planets. A copy of this proposal can be found here: [link to copy of IAU proposal by Dr. Stern and others]. We’ll have to wait and see whether Pluto will remain a “dwarf planet” and whether and how use of the term “planet” continues to evolve over time.

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