It was a beautiful evening as I drove home from work. The clear air allowing appreciation of all five volcanoes that loom over South Kohala. Indeed, the horizon was completely clear, the island of Kahoʻolwe visible over 60 miles away.
As I drove I noted the Sun beginning to settle into the distant horizon. At the wheel I couldn’t look long enough to be certain, but I thought I saw an Etruscan vase effect as the solar disk made first contact with the horizon. Curiosity peaked, I pulled over to properly watch the end of sunset. A pleasant surprise rewarded my view, a decent green flash was apparent as the last glimmer vanished.
Better yet, the camera caught the effect as well. Of the dozens of sunsets I have stopped and watched, this was the best green flash seen yet from such a high elevation. Still, it was modest compared to a couple flashes I have seen from sea level. I can only wonder how good this evening’s flash was as seen from the shoreline, 2,000 feet below.
A modest green flash as seen from the Mamalahoa Highway outside Waimea, 1 Dec 2011
For meteor watchers there is probably no more anticipated show that the annual Leonid Meteor Shower. The Leonids are renowned for reliable showings featuring bright fireballs.
The reputation is not without reason, Leonid events over the last decades have produced spectacular showers. The 2001 Leonids have become legendary, for a few brief hours on the morning of November 17th the shower became a true meteor storm, with rates of more than one thousand meteors an hour visible across the western United States and the Pacific. The sky was constantly peppered with streaks, many dim, but some very bright, every few minutes a fireball would be brilliant enough to light up the landscape. Other observers will mention that the 1998 Leonids produced a impressive number of bright fireballs, making that year particularly memorable.
1833 Leonids, the engraving is by Adolf Vollmy based upon an original painting by the Swiss artist Karl Jauslin, that is in turn based on a first-person account of the 1833 storm by a minister, Joseph Harvey Waggoner on his way from Florida to New Orleans.Nor is the 2001 event unprecedented. This has happened in the past, with Leonid meteor storms occurring several times in the last couple centuries. In 1833 a massive shower woke residents across the eastern United States with a fury that had many thinking that Judgment Day was upon them.
The Leonid meteor storms incited terror and religious revelation, but also stimulated the study of meteor science. It is from studies of these storms that astronomers began to realize that meteor showers were natural, and predicatable phenomena. This led to the realization that the annual meteor showers were associated with comets with orbits that cross the orbit of the Earth.
Just how impressive a show depends on a set of complex factors, meteor prediction is not an exact science, but astronomers are getting steadily better at these predictions. The meteoroids are found in clouds of debris left behind by a comet. In the case of the Leonids this is comet Temple-Tuttle, which has an orbital period of 33 years. All along the orbit of the comet there is a cloud of debris, small bits of dust and sand sized grains of rock-like material. Prediction is a matter of figuring out how this material will move about under the influences of gravity from the various planets and other factors like the pressure of the solar wind and even sunlight.
Unfortunately for meteor watchers, the 2011 Leonid shower is expected to be fairly weak, with ZHR rates around 20. There are some predicted peaks, due to specific regions of debris left behind by the comet several centuries ago, but the average meteor size is predicted to be quite small, leading to to faint meteors. This is further complicated by a bright waning gibbous Moon present during the shower peak. This is probably not a good year for Leonid observing.
Waimea is a place of rainbows. So common are they here it is a rare day that goes by without at least one rainbow.
But what does a rainbow look like at sunset? When the Sun’s light is reddened by passage through so much air and haze. The bow will begin to lose all color except for red, this creates a red bow…
A snow covered Mauna Kea at sunset as seen from Wiamea, with a bit of a red sunset bow above the western slope
I am waiting for the Moon to leave the evening sky before shooting the comet again. In the meantime I am processing more of the material obtained earlier in the month. In this case a photo of Comet 103P/Hartley 2 taken October 6th with Keck 2 and DEIMOS. The image marks the first time I have attempted to take and process an image with a 10m telescope. Just a wee bit larger than the 76mm refractor I usually use to take astrophotos!
The image is notable for its complete lack of any interesting structure. There are no jets, shells or other inner coma detail visible. The tail is simply a general brightening to the southwest (lower right in this image).
The comet is moving very quickly across the sky, even more so with the high magnification lent by a large telescope. Even short exposures turn the stars into long streaks. In this case multicolor streaks as the camera cycles through the filters needed for a color image.
Comet 103P Hartley 2 with Keck2 and DEIMOS 6Oct2010 @ 7:27UT, 3x60s, 3x60s and 3x120s with standard BVR astrometric filters, credit: Cooper/Wirth/W.M. Keck Observatory
A lunar halo may be quite pretty, but along with pretty sunsets, it indicates lousy sky conditions for astronomy.
In this case a high layer of thin cirrus, consisting of small ice crystals, cover the sky. The crystal shape is just right to bend the light at a specific angle, creating a halo 22° from the light source. A faint hint of color can be seen at the inner edge of the halo.
Thanks to all of those folks who posted comments about meteor fireballs. As I mentioned, these sort of events are not all that uncommon, and occur regularly across the globe. What is unusual is good photos of the event. This did happen this week, a photographer had a good camera at the ready when a similar fireball came in over Groningen, Netherlands on October 13th. Great photos of an event much like the one we saw last week over Hualālai. Check out his page for the full set of photos including the final breakup, the website is in Dutch, but a Google translation will let you follow the description.
Looks like several folks saw this meteor come in, including the entire evening crowd at the VIS. Another report from Kali on Maui emphasizes just how bright it was.
Larry O’Brian reports from the VIS…
The highlight of the evening was unquestionably a spectacular fireball that burned brilliant green, slow- moving, threw off at least one fragment, the whole enchilada. No sound, other than thirty people shouting ‘wow!’ I first caught it around, say, Aquila heading towards Ophiuchus, but people were already calling out about it.
Between Larry’s excellent report and my own sighting I can place this meteor coming in steeply somewhere over or just south of Hualālai. From around the summit to out to sea beyond Kealakekua, much closer than I would have thought. Given the breakup and low altitude the proximity implies there could have been pieces reaching the ground. Anyone in South Kona report something hitting their roof?
Any readers want to join me search an entire 9,000ft volcano for meteor fragments? Spotting dark fusion crusted meteors on top of fresh black a’a basalt ought to be easy… Not!!!
Nice meteor fireball just a few minutes ago. Just as Deb and I were driving down Waikoloa Road, about 8:06pm, due south over Hualalai. It lit up the landscape a bit, very bright, with fragments flying off as it came in.
Given the time, mid-evening with dinner events and Iron-Man festivities underway, I suspect more than a few people along the coast noticed this one.
The clouds have not been kind to those of use hoping to observe a comet here in Hawai’i. Last night Deb and I were at the Mauna Kea VIS, volunteering with the evening stargazing. I had hoped to get a good look at the comet from a dark site. But the clouds kept me from seeing the comet at all. A few people did get a look when a hole in the clouds allowed a glimpse, but by the time I got to an eyepiece the clouds had again closed over Leo, obscuring the view.
I did get a few hours of decent skies a few nights ago from the driveway in Waikoloa. I took advantage of that time to get twenty four minute exposures with the Canon 20Da and forty exposures with the CCD camera. Unfortunately the streetlights precluded my getting a decent visual view. The camera did a bit better, revealing some interesting structure to the tail.
Processing the image proved to be quite a challenge. The comet is moving very fast against the background stars. Aligning the images on the stars turns the comet into a long blur, likewise aligning the images on the comet creates streaks in place of stars. The answer is to process the image both ways and add the two resulting frames together as layers in Photoshop. This is the first time I had attempted this process and the results are reasonable…
Comet C/2007 N3 Lulin on the morning of 22 Feb 2009
Damon alerted us to a nice display of a lunar halo currently gracing the skies over the Big Island. A nice example of a common 22° halo that can occur any time there is a thin layer if high cirrus. The 22° angle from the Moon is a result of refracting moonlight through ice crystals. These high altitude crystals act as little prisms, catching and deflecting the light at specific angles. The halo is actually very large, extending from 22° to 50° away from the Moon, but is brightest at the inner edge.
A 22° lunar halo produced by ice crystals high in the atmosphere over Hawai’i on 8 Dec 2008Halos like this are really quite common, but always seem to catch the attention of those who do not regularly watch the sky. There are many fantastic sights that occur regularly around us, all we have to do is keep an eye to the sky. It has taken centuries to learn how these effects are created though the play of light and water, even now there are some that are poorly explained. It is fascinating to learn what can occur and how it works.
There is a great website, Atmospheric Optics, that has examples and explanations for the many beautiful effects that the play of light can create in the atmosphere. Sun dogs, rainbows, parhelic arcs, glories, specters and more.
This halo is fairly broad and ill defined, probably because the ice crystals are randomly arranged. The halo could be sharper if the crystals were all at the same orientation to us, something that can occur if the winds are right. I attempted a shot of this one, the first time I had attempted to photograph a lunar halo. Not the greatest photo, this was pressing the camera to it’s limit. Even so the image starts to show effects invisible to the human eye, including a hint of color at the inner edge of the halo.
