(meteorobs) Aug 12 Session Summary

[Robert Lunsford]

Since a cloudy July in this part of the USA, August has been incredibly clear, at least for the areas east of San Diego above 3K feet. There was a lot of monsoon action to our east in July which produced many cloudy night last month. These clouds were mostly alto cumulus,  which are higher than the local mountains. The nocturnal clouds (if any) we have seen this month are stratus limited to the coastal areas less than 3K in elevation. These clouds actually act as a shield and reflect some of the city lights back to the ground. 

The sky seen from the western slopes of Mt. Laguna was impressive during this session as the light dome was limited to a small strip low along the western horizon. Still, the western sky was far from perfect and probably a half magnitude brighter than the eastern half. Low lying hills to the east blocked any lights from the desert communities so the eastern sky appeared pristine. I was facing east at an elevation of 60 degrees enjoying the summer Milky Way as it stretched from Aquila down through Auriga. It struck me how prominent the constellations of Cassiopeia, Perseus, and Auriga were with their many bright diamonds sprinkled along the Milky Way. I was about to say shimmering but the seeing last night was fantastic and the stars above 30 degrees showed no twinkling whatsoever. Had it not been such a great night for meteor watching, I would have certainly had my telescope out.

The Perseid activity was about what I expected for the first hour. Two graceful but fairly dim Kappa Cygnids darted downward through Andromeda. The other minor showers were quiet this first hour.

Activity ramped up during the 2nd hour. The brightness of the Perseids was similar except for a -5 fireball that occurred at 1:33 AM PDT and a strange spike in 2nd magnitude Perseids, 3x more than any other magnitude. At 1:50 AM I noticed my recorder was malfunctioning so the last 10 minutes of this hour was lost fixing it. No actual data was lost but the playback was somewhat garbled. I make it a habit to check the recording quality every hour to make certain all is well. I have heard too many horror stories where an entire night's data was lost due to a faulty recorder.

After a slow start to the 3rd hour, the activity really picked up. The gaps in activity were few and many minutes produce multiple meteors. Several 60 second periods produced 3 and 4 Perseids, often seconds apart. Possible members of the Alpha Triangulids and Eta Eridanids were seen during this time as well as activity from the Delta Aquariids. An impressive 13 negative magnitude Perseids were seen during this period.

At the start of the 4th hour my son retired to the truck to sleep so I grabbed his better lounge chair and ended up taking a 14 minute break to stretch and have a snack. The remaining 46 minutes were very active with very few lulls in the activity. A remarkable occurrence was seen at 3:40 AM PDT when 4 consecutive negative magnitude Perseids were seen in a 90 second period. Two of these occurred just seconds apart with the train of one meteor fading while the other meteor appeared. Interestingly, the sporadic counts fell by nearly 50% during this period. My break would account for half of those.

My last hour usually produces a drop in activity that may be due to fatigue and/or the oncoming dawn. Actual Perseid numbers were higher this hour but if one factors in the break during the previous hour, then that hour was more active. Regardless, there were many Perseids seen in the zero to +4 magnitude range this last hour. The negative magnitude Perseids that did appear seemed to shoot down toward the northeastern horizon. Strangely, with the radiant nearly out of my view, my only Anthelion activity was seen during this hour. Sporadic activity was back to normal with 11 being seen. 

All in all, it was a fantastic night, much better than anticipated as recent Perseid displays have been somewhat dull for me. This was much more like the impressive displays of the late 70's through the 90's when the Perseids often challenged the Geminids as the top display of the year. 

On a side note, Algol was near maximum brightness and rivaled  nearby Mirfak. Mira was also easily visible and estimated at magnitude +4.0. It was also interesting to follow the zodiacal band which started out parallel to the Milky Way and then shifted as the night progressed until it met the Milky Way in Gemini.  The gegenschein, currently located in Capricornus, was not visible.  

Magnitudes of Minor Radiants and Sporadics:

ANT: +3 (2)  +5 (1)  Mean: +3.67

ATR: +2 (1)  +3 (1) Mean:  +2.50

ERI:  +2 (1)  +3 (1) Mean:  +2.50

KCG: +3 (1)  +4 (1) Mean:  +3.50

SDA: +3 (2)  +4 (1) Mean:  +3.33

SPO:  0 (1)  +1 (1)  +2 (6)  +3 (10)  +4 (15)  +5 (6)  Mean: +3.41