Jane Houston Jones » International Meteor Organization

Counting meteors from Amboy Crater – Lyrids 2012

jane — Thu, 03 May 2012 20:33:50 +0000

Amboy Crater at dawn

2012 Lyrid Meteor Shower Meteor Profile showing peak near 04h-06h UTC

My visual meteor observing report with 30 minute (or less) intervals, and magnitude distribution

Saturday night, April 21, Mojo and I headed to our new favorite dark sky spot, Amboy Crater, one of the darkest observing locations in the US. This spot has great horizons and its remoteness keeps all but the serious observers away, though we’ve met delightful observing buddies at this spot. Our one way drive from Monrovia, CA is 170 miles, fyi.

After a night of observing, you can’t beat the morning hike to Amboy Crater, a 6,000 year old volcanic cinder cone, either. Even in the summer it’s cool at dawn. Look carefully at the oxidized lava beds as you follow the hiking trail to the crater and you might find some Chuckwalla lizards! Chuckwallas can reach 16 inches in length, weigh up to 2 pounds and are specially adapted for desert living. Chuckwallas are my very favorite herps, well, next to the desert tortoise, that is.

The peak of the Lyrids occured at 1:30 a.m. Eastern (10:30 Pacific). The constellation Lyra was barely above my horizon at that hour. This meant the highest rates were probably recorded several time zones east of my California location. I set up my observing area, shut my eyes until about 11:00 p.m., and then I managed to observe straight through the night — from 11:40 p.m. until just before dawn at 5:16 (6:40h – 12:16h UT).

Here are a few tips I use to prepare myself for a night of meteor counting. First, I read Bob Lunsford’s weekly meteor shower recap on the Yahoo meteorobs group email list which discusses amateur meteor astronomy. It’s a good place to “lurk” and learn.

Bob wrote “The Lyrid (LYR) shower is expected to reach maximum activity on the night of April 21/22 with rates up to 15 shower members per hour. The radiant is located at 18:08 (272) +33. This area of the sky is actually located in extreme eastern Hercules, eight degrees southwest of the brilliant blue-white star Vega (Alpha Lyrae). The radiant is best placed just before the break of dawn when the radiant lies highest in the sky. While Lyrid meteors can be seen in both hemispheres, the north is favored as the radiant lies much higher in the sky. Rates will fall rapidly after maximum and little activity will be seen the remainder of the week. At 48km/sec. the Lyrids would produce meteors of medium-swift velocity. It should be noted that the Lyrids can occasionally produce bright meteors of fireball class magnitude.”

Next I familiarized myself with the spring sky and printed out some all-sky charts, marking the radiant between Lyra’s bright star Vega, and the Keystone section of Hercules. I then decided where to look — 50-70 degrees above the horizon, 20-40 degrees away from the radiant. I selected the area around the bright star Arcturus in the constellation Bootes. When counting meteors you don’t want to look directly at the radiant as the meteors will look like short streaks, or points of light.

For this shower the rates were not expected to be too high, so I decided to record (for my first time) the magnitude of each meteor. I made a note of the magnitude of Saturn, Mars and Venus and re-familiarized myself with the magnitudes of many bright stars nearby during my prep time. Then, I selected two small constellations (Corona Borealis, and the head of Draco) which contain magnitude 2-5 stars and memorized their magnitude.

Armed with all these stellar magnitudes, I settled down and waited for it to get dark. Once it did, I began the first important observation — estimating the limiting magnitude. The limiting magnitude is the magnitude of the faintest star near the zenith that the observer can detect using the slightly averted naked eye. It defines both the condition of the sky’s clarity and the quality of the observer’s eyes. I keep a set of these charts on a clipboard and take them with me on all observing trips, even if I am not observing meteors. Every 30-45 minutes, between my half-hour counting sessions, I re-counted the stars in the selected areas, to note any changes in the sky clarity or the condition of my own eyes.

In a nutshell my skies were Magnitude 6.5, which is very dark. Weather conditions: clear, 98 degrees at sunset, 62 degrees at dawn. It was a shirtsleeve weather night almost all night long, tho’ I put on a fleece jacket at about 4 a.m.

Between 11:40 p.m.and 5:16 a.m. (06:40h – 12:16h UT) I counted 36 Lyrids, 6 Sporadics and 2 Anthelion meteors. A quarter of the Lyrids I saw were very bright -1 or brighter meteors. I took short breaks between counting sessions to re-estimate the limiting magnitude, have a snack, check on what Mojo was imaging through his telescope, stargaze through my own scope, etc.

06:40h-07:10h UT – 7 Lyrids
07:30h-08:00h UT – 3 Lyrids
08:15h-08:45h UT – 5 Lyrids, 1 sporadic
08:50h-09:20h UT – 5 Lyrids, 1 sporadic
09:30h-10:00h UT – 6 Lyrids, 2 sporadics
10:05h-10:25h UT – 1 Lyrids, 1 sporadics, 1 Anthelion
Break to look at Saturn, have a snack, scan Milky Way
10:59h-11:29h UT – 2 Lyrids, 1 Anthelion
11:30h-12:00h UT – 7 Lyrids (2 fireballs!)
12:01h-12:16h UT – 1 sporadic

You can see that I saw the most meteors just as I was getting started (which was near the peak) and again near dawn (when Lyra was at its highest in the sky). Just before 5 a.m. 12h UT both Mojo and I saw a very bright bollide, greenish in color in the western sky. I estimated its magnitude at -5, brighter than Venus. It probably was much brighter. Coincidentally, 3 hours later an even more impressive bollide streaked across the California Sierra foothills, and broke up in the atmosphere, sprinkling meteorites over a wide populated area. Both of these bollides were Lyrid fireballs!

My other Meteor blogs and adventures

Flying through the Leonid Storm of 1999 – aboard USAF’s ARIA from Edwards AFB

Leonids 2002 – aboard NASA’s DC-8 from Dryden Flight Research Center

Observing meteors from the city – yes you can!

My meteor observing gear

January Quadrantids and a demoted constellation

August Perseids and meteor recording tips

Lyrid 4/22/12 fireball movie with radiant map

Mojo’s astrophotography from Lyrid shower night

Viewing meteor showers from light polluted LA – not impossible!

jane — Mon, 09 Jan 2012 05:17:29 +0000

The white area is greater Los Angeles. I observed from my driveway in Monrovia, indicated at the "red/white" border zone marked with cross-hairs

My meteor watching setup - comfortable chair, blanket, clipboard, red flashlights, clock, binoculars, snacks

The graph shows the ZHR (Zenithal Hourly Rate), which is the number of meteors an observer would see under a very dark sky with the radiant of the shower overhead. (this chart is being updated as more reports are submitted)

I prefer to drive far from LA to view meteor showers from a dark sky, but those darn showers don’t always happen on weekends or days I can take off work. So this week, I observed the Quadrantid Meteor Shower from my bright moonlit Los Angeles County driveway until after midnight, snoozed until moonset at 3:00 a.m., then had a fairly decent sky from 3:00 a.m. to 5:15 a.m. when the sky started to brighten from the dawn light. Although I didn’t see many meteors, and only one before the moon set at 3:00 a.m. PST January 4th, I was thrilled with my observations.

Take a look at this colorful map. See that white blob? That’s Los Angeles on a light pollution map. That white ribbon? That’s the California coastline. White on these maps designates the most light polluted areas in the world. There is no worse place for light pollution. LA is the model of a major metropolitan meteor-observing maelstrom of star-obscuring light pollution. This white color on the map is described in bleak terms on the Clear Sky Chart website’s light pollution map page: “The entire sky is grayish or brighter. Familiar constellations are missing stars. Fainter constellations are absent. Less than 20 stars visible over 30 degrees elevation in brighter areas. Limiting magnitude ranges from 3 to 4. Most people don’t look up.” Monrovia is on the north edge of the white blob that is Los Angeles, indicated by the cross-hair. (all those little crosses on the map are other astronomy locations). Red is the next to worst light pollution zone, and the ribbon of red color next to Los Angeles is the San Gabriel Mountain foothills. Monrovia is nestled between the Los Angeles basin and the mountains. It’s fine for moon and planets at our monthly Old Town Sidewalk Astronomy nights, not so good for meteors and anything else astronomical.

The three oval white blobs on the left lower quadrant are Santa Catalina, San Clemente and San Nicholas Islands! The yellow, green and blue zones are in the ocean. It’s even light polluted well off the coast of Southern California!

I usually drive 150-300 miles to one of the black teardrop shaped pin spots on this light pollution map of California. Those are the best and darkest locations for the stargazing and astrophotography we enjoy. Mojo and I prefer Amboy Crater, Hole-In-the-Wall Campground in Mojave National Preserve, and a spot near Desert Center 60 miles past Indio on I-10. We also love the dark skies at Glacier Point at Yosemite.

But this week was the peak of the Quadrantids, and I didn’t want to drive a 6-hour round trip for 3 hours of meteor watching, especially on a work night. So I found a good spot in my driveway and it blocked a lot of the local light sources. I nestled my comfy observing chair up next to a cinder block wall. This wall, plus strategically placed tall trees blocked the moonlight and oncoming car lights from my view. To my south was not the Milky Way, but the milky gray — the color of skies over Los Angeles. I could see the big dipper stars, and part of the little dipper. Below these two constellations was the radiant of the Quadrantids. This area wouldn’t even rise until after midnight, but I wanted to say I observed the Quadrantids during the actual peak, and check for earthgrazing meteors on the horizon.

I estimated my limiting magnitude at a dismal 3.9 using star counting charts. I settled into my meteor-watching chair, sipped some hot green tea and waited. And waited. And waited some more. From 11:00 p.m. until 12:30 p.m (PST) I saw exactly one meteor, and it wasn’t even a Quadrantid. The moon was high overhead now, and so I snoozed until moonset at 3:00 a.m. Wednesday morning.

When my alarm went off, I headed back out to the driveway. I adjusted my chair, adjusted the dark blankets I placed over the fence between my driveway and the neighbor’s all-night security lights. By careful placement of my head, and with blankets on the fences and shrubs I had no lights shining directly at me.

It was a little after 3 a.m. and I started observing an area above the radiant, centered on the bowl of the big dipper. My back was facing the well-lit LA basin, my view to the north was overlooking the San Gabriel mountains and Mt. Wilson Observatory. By 3:18 I had seen my first Quadrantid. At 3:30 I counted stars again. Without the moonlight, my limiting magnitude rose to a respectable 5.1 using this star counting chart. I repeated this exercise several times, until I could barely see stars after 5:00 a.m. My last limiting magnitude calculation before I packed it in was 2.9.

This chart shows the data from 48 observers in twenty countries. Data (still coming in, I’ll update the chart a couple of times) is averaged based on the observers seeing conditions, visual acuity, cloud cover percentage, etc. You can see that the highest rates — at the peak of the Quadrantids were in excess of 80 per hour. This is the number of meteors which would be seen overhead at the zenith (in a dark sky) if the highest rate was kept steady for one hour. In reality, the highest rates last usually for only a few minutes for showers like the Quadrantids with a very narrow peak. How many did I see from my Monrovia driveway? I saw three from 3:00-3:30 a.m. and another three from 3:30-4:00 a.m. I saw five from 4:00 to 4:30 a.m. and between 4:30 and 5:00 a.m. I saw three, plus heard nearby roosters crowing! I finished the observing with 2 more Quadrantids between 5:00 and 5:15 a.m. and was heralded by a veritable rooster symphony as the sky brightened. My total count over a little more than 2 hours was 16 lovely Quadrantids, two sporadics, and one Anthelion! Here’s my report which I submitted to the International Meteor Organization. Amazingly, this number is almost exactly the prediction from NASA’s Meteor Fluxtimator when I entered Quadrantids from downtown Los Angeles on the 3rd and 4th of January 2012. How about that! You can observe a meteor shower from Los Angeles!

Here’s the meteor shower calendar for 2012

Interested in counting meteors? Here’s the IMO Visual meteor observing form plus instructions and FAQs

More about the Quadrantids and their namesake constellation, Quadrans Muralis

Post-Perseid depression (or how to observe meteor showers)

Perseids from Amboy Crater (a dark sky site)

The Perseids from Amboy Crater

jane — Tue, 26 Oct 2010 23:51:06 +0000

Perseid Peak Aug 12-13 18h-7h UT

My Perseid count Aug 13 06h-11h UT

Sunset at Amboy Crater, with moon and Venus

Amboy Crater by day

For the past year I’ve been traveling to dark skies to observe and count meteors during the major showers. Armed with a clipboard and a comfy chair, I stare at a section of the sky, hoping to see members of the well known showers, and contribute my data to that of other meteor observers around the world.

This writeup is really about how I observed, recorded and submitted my 2010 Perseid meteor shower data to the International Meteor Organization. I hope I inspire you to try it, even if you don’t submit your paperwork the first time. (I didn’t, in fact it took me longer to fill out the paperwork the first time than it did to actually observe the meteors!).

The first chart shows the peak of the Perseids – August 12-13 between 18h and 7h Universal Time. That means for people like me on the west coast of the US, the peak was nearly over before I started counting! It’s important for worldwide observers to keep counting, because many showers have secondary peaks or other characteristics.

The second chart is my data. Before I arrived at the site, I recorded the latitude, longitude, elevation and name of my observing location. This is easy to do using your GPS devices these days. I wrote down my name, my IMO codename (JONJH) and the shower (Per for Perseids). I decided not to try and identify individual minor showers though there were many. I called all non-Perseids Sporadics.

Before I began observing, and several times during the night I assessed the darkness of the sky using Limiting Magnitude star charts. This field is identified as LM on my observing form. The IMO says: “The darker and more transparent the sky and the more sensitive your eyes, the more meteors you can see. To use your observations for scientific analyses a quantitative characterization of these factors has to be established. The limiting magnitude (which is defined as being the magnitude of the faintest star near the zenith that the observer can detect using the slightly averted naked eye) defines both the condition of the sky’s clarity and the quality of the observer’s eyes.”

I keep a set of these charts on a clipboard and assess the sky darkness every time I observe. My assessment was a very high limiting magnitude. I could see magnitude 6.5 stars with my unaided eyes.

On a clipboard, I clipped a bunch of blank sheets of paper – one piece for each hour of the night. I wrote down each meteor I observed and noted the time using a nearby clock. I also wrote down the magnitude of each meteor – using a shorthand of 5 magnitudes of brightness. (F for faint-mag. 4, B for bright mag. 1, etc. J for Jupiter bright bolides) I had a selection of stars in the area already memorized for comparison against the Perseids. For spectacular meteors, I plotted them on star charts I had printed out for this purpose.

In a nutshell: Mag 6.5 skies, clear, 80 degrees overnight. Amboy Crater, one of the darkest observing locations in the US, was a great location for meteor observing.

Between 9 and 11 p.m. (04h-06h UT) I unofficially saw about a dozen mostly very bright meteors while setting up my chair, eating dinner, etc. I didn’t start seriously recording the meteors until 11 p.m. (06h UT)
04h-05h UT – 2 Perseids, 1 sporadic
05h-06h UT – 4 perseids, 3 sporadics **the first Perseid came in at 9:34 p.m.
06h-07h UT – 15 Persieds, 12 sporadics
07h-08h UT – I took a nap
08h-09h UT – 27 Perseids, 8 sporadics
09:19-03:19 – 43 Perseids, 3 sporadics didn’t take a break since the rates were so high…
03:20-04:20 – 39 Perseids 1 sporadics (with a 7 minute break)