Sunday, March 16, 2014

Sunday March 16, 2014 - March Meteors Observed in 2007

  After plotting the meteor seen after midnight today, I realized that I'd made an entry in the past about meteors that seemed to radiate from this area of the sky in early March. This morning I started going through old logs and found the record . The observations had been on two consecutive nights; the mornings of March 11 and March 12, 2007. I'd seen a total of three meteors, and when I plotted them on a chart printed off the Heavens-Above website, then extended their paths in the sky backward, all three meteors seemed to converge at a point close to the bright star Arcturus in Bootes. I thought that maybe I was seeing a Minor Meteor Shower at the time. Here's the plot that I made seven years ago ... though after studying materials about visual meteor observing, I realize now that this plot has some issues! I'll describe these also.

  Meteor #1 was seen at 1:35 AM (6:35 UT) on Sunday, March 11, 2007. It was about 1.0 magnitude and fast with no train, and seemed to cross right through Bootes.
  Meteor #2 was seen just one minute after the first one, at 1:36 AM (6:36 UT) Sunday, March 11, 2007. This one was fainter at 3.0 magnitude, fast, and also had no train. It zipped from near the star Arcturus to south of Corona Borealis.
  Meteor #3 was seen the following night at 1:15 AM (5:15 UT) on Monday, March 12, 2007. (Daylight Saving Time had occurred after the first two meteors were observed, hence the difference in UT conversion from one night to the next!) This was a bright meteor of about 1.0 magnitude that was fast with no train, and it zipped from the southern part of Ursa Major all the way to the constellation Gemini.

  Here are the problems with this plot that I made back then. First of all, I realize now that to be really accurate, one has to plot meteor paths on a chart that uses gnomonic projection, like the BRNO Atlas that I've downloaded from the IMO website this year. Secondly, I didn't realize until reading through IMO materials that there's a relationship between the apparent meteor path length and the radiant. From what I understand now, at least for meteors higher than 30 degrees, the distance between the radiant and the start point of a plotted meteor has to be at least twice as long as the meteor path itself. Using this general rule, the first meteor I saw probably originated from a radiant between and south of Virgo and Libra, while the second one probably had a radiant southwest of the brighter stars of Virgo. The third one may have had a radiant as far away as Serpens. Of course I'm still making these estimates using the wrong kind of chart and I'm also assuming that the path lengths of the three that I drew seven years ago are accurate.

  I think now that the first two meteors could have been from the almost-year-long Anthelion source, like last night's meteor may have been. The only problem with this is that I described the speed of all three meteors then as "fast" and Anthelion Meteors are lower in velocity than most other types. It's possible that all three of them were just random Sporadics also.

  If nothing else, going back to this entry from 2007 shows me that my own observing methods for meteors are evolving over time! As the year goes on I hope to get out to do more plotting and counting during the major and minor showers so I can contribute some good data to the IMO. There's still a lot about meteor showers that remains to be discovered. It's a wide-open area of amateur astronomy!

AM Sunday March 16, 2014 - PostScript

  Seeing the meteor tonight in this chilly predawn mid-March sky has prompted my memory a bit ... I know that several years ago I documented a couple of meteors in early or mid March that were also in this part of the sky near the constellations Bootes and Corona Borealis. I'll try to find the notes I made then and publish them here soon. In hindsight these may also have been Anthelion Meteors. It's also possible (but not probable?) that there's a minor meteor shower that's active this time of year. I'll do some note searching and research to see if I can find anything!

AM Sunday March 16, 2014 - Observing Notes - First Meteor of 2014

  Although skies were clear at sunset, afterward for most of the night we had on-and-off scattered high clouds in the area, There were long periods of clear sky and then long periods of scattered high clouds. The Moon was just hours from Full in southern Leo, so it was a bright night. Winds picked up and became gusty after dark and the temperature dropped rapidly. On Saturday we'd been in the mid-50's F but by 1:00 AM we were down to 35 F with a wind chill of 26 F.

  Though I played around a lot with the idea of getting out in the lawn chair to do my first "professional" meteor watch of 2014 to report to the IMO, the scattered high clouds and moonlight discouraged this. I walked out into the back yard several times from evening through after midnight to assess the sky conditions, but whenever I thought the sky was clear and I got motivated to do the meteor watch, I'd go outside fifteen minutes later to find out that more cirrus clouds had drifted in!

  However, the night wasn't a total loss. At 1:09 AM (5:09 UT March 16) I spotted what turned out to be the first meteor I've seen and documented in 2014! It was 2nd magnitude and fairly slow-moving. I spotted it over the roof of our house as it passed from Corona Borealis to Hercules, where it flared out. It left a very brief train in its wake that lasted probably a second or less. I took the time to really note the position in the sky where I saw it begin and end, and the time that I saw it. Then I made careful notes when I was back inside the house.

  The plot below was made from memory using the BRNO Atlas sheet #5. The meteor itself is in the upper left corner with the arrow showing the direction of movement. I also plotted the rough position of the Anthelion Radiant in the far lower right corner, because I'm fairly sure from its slow speed, path length, and direction that this was an Anthelion Meteor that I spotted this morning.

    The sky was so clear after 1:00 AM that I thought about getting out for about an hour again to do the meteor session, but when I went outside just before 2:00 AM high clouds had started to drift in all over the sky again. There was a very impressive bright ring around the Moon that extended through the Sickle of Leo to the eastern edge of Leo and Virgo, and faded away to my south where the tree branches obstructed some of the view.

Saturday, March 15, 2014

PM Saturday March 15, 2014 - Notes

  Full Moon will occur at 17:08 UT March 16, or 1:08 PM EDT tomorrow. The sky has been mostly clear today with scattered high clouds. The ground is totally free of snow cover, and this is the first day since New Years Day that I can't find even a trace of snow in my front or back yard. After a very cold middle of the week it's been mild yesterday and today. Another wave of cold air is forecast for Sunday and Monday. I may get out to do some observing after sunset if conditions are decent in spite of the moonlight.

Thursday, March 6, 2014

Thursday, March 6, 2014 - Brief Notes

  When one observes outside with a telescope that runs off AC power from an outlet on the side of the house, and the patio has been covered with piles of snow for most of the last three months, one ends up doing very little observing! If you measure the winter season as December 1 - February 28, Indianapolis just ended its record snowiest winter in history. It's been more than 30 years since a season this bad; not just with the snowfall, but also the number of nights with below zero (°F) temperatures.

  The good news is that March is here. It started off with a snow and ice event on Sunday the 2nd and a couple of much colder than normal days following it. But as we reach the end of this first full week of March, temperatures are starting to moderate, a lot of the snow is gone, and the urge to get out and do some meaningful amateur astronomy is growing!

  I'm currently researching neglected Eclipsing Binary stars and good spring and summer YSO targets to start regularly observing. I'm also planning to do more meteor shower work and hopefully lunar observing. After a long dormant period, I hope to start getting out under the night sky soon and posting my observations here again.

Monday, April 8, 2013

AM Sat. March 30, 2013 - Lunar Observing (Part 3)

  While I was photographing and observing the Moon that morning, I also managed to take some decent photographs of the Aristarchus / Herodotus area and also observe it with the eye under high power.

  I've gotten involved over the last few months with the Repeat Illumination Event Program run jointly by the Association of Lunar and Planetary Observers (ALPO) and the Lunar Section of the British Astronomical Association. This program is coordinated by Dr. Tony Cook in the U.K.The goal of this program is to observe and also sketch or photograph features on the Moon that have been the sites of TLP (Transient Lunar Phenomena) reports in the past, when these sites are under the same illumination and libration conditions as they were when the reports were made. That way, if the area shows a color change, an unexplained bright area, or an apparent obscuration, then there's evidence that this isn't just a random event since it would have appeared that way more than once at the same sun angle.

  The Aristarchus area is the place on the Moon where the most TLP has been reported. Observers have supposedly seen brightness changes (it's the brightest crater on the Moon anyway) and sometimes red, blue, or other colors within and around it. The nearby crater Herodotus has also been the site of some of these rare reports. Though it has a smooth floor (and this has been proven on photos taken by spacecraft orbiting the Moon), there are rare instances where experienced observers have seen what looks like a bright central peak in it. Some thing this could have been caused by a temporary cloud of dust catching the sunlight, raised by an out gassing event. There have also been clouds and color changes reported in a nearby wide area of Vallis Schroteri (Schroter's Valley) called the "Cobra's Head."

  The location of Aristarchus / Herodotus is shown on the photo of the Moon below (a photo I took on March 30) using a red square.

  The photograph below is one I actually took earlier this year on the morning of February 24. This shows the Aristarchus area under better lightning conditions than it had on March 30, but I wanted to throw in some labels showing the major feature. (South us up in these photos, since this is how it appears through the telescope eyepiece.)

  On the morning of March 30 between 5:27 - 6:27 UT (1:27 - 2:27 AM Eastern Daylight Time) this area was under repeat illumination conditions of a TLP observed on August 26, 1964 by Gennatt. The report on file for that event almost 49 years ago reads like this:

  Aristarchus  1964 Aug. 26 UT 02:00 - 03:00 Observed by Gennatt, Reid (Greenbelt MD 16" reflector, x360, S=P-G) and Lindenblad (Washington DC, USA, 26" refractor) "Red and Blue bands. Grew thinner & shorter. Alerted Naval Obs. One obs. tho't he saw Phenom. but not sure. (confirmation?) (prof. astronomers, but not lunar observers)" NASA catalog weight = 5 (very high). NASA catalog ID #844

  I spent about 20 minutes gazing at Aristarchus under high power between 1:25 AM - 1:45 AM (5:25 - 5:45 UT) on March 30. The Seeing was about a 7 out of 10; there were actually long moments of steady viewing with occasional atmospheric "rippling" which was good considering the Moon was never more than 25 degrees high in the South-Southeast sky. The Transparency was only about a 3 out of 6. Though the telescope I was using was much smaller than the ones listed in the 1964 report, I was unable to see any red or blue bands or any other color changes in Aristarchus during that time. I was able to pick out at least two of the "normally seen" dark bands on the western rim of the crater. I also noted that the dark area surrounding Aristarchus really stood out tonight, though I didn't think it looked unusually dark. I was able to get a pretty decent photo of the area at 1:40 AM when the terminator longitude was at 129.39 degrees. The photo is below:


  I sent my report and the photo to Dr. Cook, and the next day he emailed to let me know that I'd get a mention in the May TLP newsletter. If so, this would be the second time for me.

  My goal is to observe this area and image it as often as possible, whether I'm seeing it during a repeat illumination event or not. I'm collecting photos of it under as many different lighting conditions during each lunar cycle as I can in order to get a good idea of how Aristarchus and the adjoining area looks during lunar morning, high noon, and lunar evening ... how the shadows look, which areas get brighter as the sun gets higher, and so on. I may never see a TLP (they might not even exist!) but the fun for me is in the hunt for one!

Saturday, April 6, 2013

AM Saturday, March 30, 2013 - Lunar Observing (Part 2)

  During the last post to this blog I commented on the "Mare Crisium Sunset Ray" a couple of times. I thought I'd try to post the photo of the Mare Crisium area taken last weekend along with some photos and sketches from past years to try to explain this fleeting event on the Moon a little more thoroughly.

  Mare Crisium is one of the smaller "seas" on the Moon; large flat plains of volcanic rock that are left over from giant asteroid collisions that took place billions of years ago when the Moon was first forming. It sits on the eastern edge of the Moon, and I've always found it showy because of it's dark color and because it has some pretty lofty mountains that ring it, making it a real beauty through the eyepiece when it's experiencing sunrise or sunset. This photo of the Full Moon shows the location of the Mare, using a red square:

  From two to three days after Full Moon, sunset occurs on Mare Crisium. The terminator (the line that divides day and night) creeps across the plain, craters that lie within Mare Crisium grow long shadows, and the mountains that surround it also cast shadows over the dark material of the plain. I was observing and sketching this area on the morning of February 24th, 2008 when I saw that there was a long streamer of sunlight on it's southern edge, caused by the sun shining between a gap in the mountains. I was able to see this again when I observed it on August 19th that year. Unfortunately, I haven't seen it since then. A "day" on the Moon lasts 29.5 days on Earth, and this phenomenon only takes place over a matter of hours during each Lunar Day. I haven't been able to catch the Moon at exactly the right time to see it, but hope to soon. If I do, and especially if I manage to photograph the Sunset Ray, I'll try to post it on this blog.

   To try to show what the Mare Crisium Sunset Ray looks like, and get an idea of when it might be seen, I thought it would be worthwhile to show some photos and sketches that show how this area looks as sunset happens. This is a photo I took on November 1, 2012. It shows the terminator about halfway through Mare Crisium. It's still to "early in the evening" on the Moon for the Sunset Ray to show up. Craters within Mare Crisium are showing a lot of relief because of the low sun angle and their floors are in shadow. The terminator here is at about 62.0 degrees East.

  This is the same photo from November 1, 2012 with some of the craters within and outside of Mare Crisium labeled. Mare Crisium itself is about 570 km (350 miles) in diameter. Two of the most obvious craters within it are Pierce (diameter = 11 miles) and Picard (diameter = 14 miles). Both of these craters were starting to get deep shadows across their floors. Also starting to show a lot of floor shadow was the small but sharply defined crater Greaves (diameter = 9 miles). Along the edge of Mare Crisium are two interesting flooded craters, Yerkes and Lick. These are probably craters that existed before the impact that created Mare Crisium, and when dark lava flooded that big crater that created the plain, it also flooded the floors of Yerkes and Lick. All we see are the crater rims that managed to stay intact. This photo also shows some craters around Mare Crisium, mainly for reference; Macrobius, the bright ray crater Proclus, and the flooded crater Tebbutt. The Mare Crisium Sunset Ray seems to be associated with the mountains just north of (above) Tebbutt.

  This is a sketch I made at the telescope while observing on the morning of February 24, 2008. This was the night I first noticed the Sunset Ray. It shows some of the craters that were in the photo before. The longitude of the terminator at the time was 56.9 degrees East. Since the terminator (or sunset line) moves a little over half a degree of longitude per hour, this shows how the area looked the equivalent of ten hours after the photo above it was taken. The floors of Pierce and Picard are still in shadow. Greaves also has a floor in shadow, but the shadows cast by the mountains along the western rim of Mare Crisium have nearly covered up that whole crater. The flooded crater Yerkes is still visible, but the other flooded crater Lick is also almost covered up by the mountain shadows that are starting to cover the Mare. The mountain shadows were long enough to meet the sunset line on the south (lower) part of Mare Crisium, except for the Sunset Ray which stretched across it just above the crater Tebbutt.

  This is a sketch made at the telescope of the same area on the morning of August 19, 2008; the second time that I was able to spot the Mare Crisium Sunset Ray. At the time the longitude of the terminator was at 55.8 degrees East, so it shows the area the equivalent of two hours after the first sketch, and the equivalent of about 12 hours after the photograph. The craters Pierce and Picard by this time were so deep in shadow that they looked like black ovals on the plain. So did Greaves, and it was at the edge of the shadow being cast by the mountains to the west and about ready to be covered up. Yerkes was still visible and the low sun angle made its low rim stand out more. Lick was no longer visible since it was totally covered by mountain shadow. Tebbutt was also starting to get covered by shadows. The Sunset Ray was thinner now and shorter, but still visible just north (above) Tebbutt.

   This is a photograph I took last weekend on the morning of Saturday, March 30, 2013. The longitude of the terminator here was 50.6 degrees East, so it's the equivalent of how Mare Crisium looked 22 hours after the first photograph, or how it would look 12 hours after the first sketch and 10 hours after the second sketch. Mare Crisium itself has now experienced sunset and only the mountains on the west rim are showing. (I thought the bright spot within the Mare was part of the rim of Yerkes crater when I first published photos of the Moon from Saturday in my previous post, but now I'm thinking that it's an isolated high point just inside the rim of Mare Crisium.)

  Here's the same photograph, with the craters Macrobius (diameter = 40 miles) and Proclus (diameter = 17 miles) labeled. These craters are mainly for reference so this photo can be compared to the first one in this entry.

  By compiling these photos and sketches, the Mare Crisium Sunset Ray seems to last, at most, 18 hours or so during each Lunar Cycle, but I have a hunch it can be observed for only about 12 hours at most every 29.5 days. I hope I can catch it again sometime soon, and also image it. It really is stunning to see! The fact that such fleeting details can only be seen for such a short time each month is one of the mind-blowing things about observing the Moon to me!