(meteorobs) Perseids Aug 12 from San Diego County

[Robert Lunsford]

After a day in which the sky was full of clouds from thunderstorms over the local mountains, the evening sky cleared nicely and by the time I started at 1:30am PDT, only a patch of altocumulus was left in the far western sky, far from my field of view. Meteor activity was noticeable while driving as two Perseids shot in front of me on the way up to the local mountains. Again, it was quite warm (79F) but this time no wind. The sky was very dark in the eastern half but due to the lack of cloud cover over the city, the western sky was bright with light. Since I had a hill 20 degrees high in the east I could not look in that direction. I choose to look just west of due north and about halfway up.

Unlike Saturday morning, a majority of the activity was made up of faint meteors. During the 3.5 hour watch I counted a total to 173 meteors. the breakdown was 144 Perseids, 2 Kappa Cygnids, and 27 Sporadics. I binned them into 30 minute periods with the strongest period producing 38 Perseids. All other 30 minute periods produced 20-26 Perseids. This particular peak occurred just as the moon was clearing the hill in the east. Perseid rates were steady the entire night except for this one 30 minute period, when rates were 175% higher. After the moon cleared the hill rates again fell and remained basically unchanged the remainder of the morning. 

Looking at my data, it appears I lost most of the 4th and 5th magnitude meteors once the moon was above the hill. So while the actual rates were climbing, my visibility was compromised by the moonlight. My limiting magnitude estimates also plunged after moonrise with it falling from a peak of +6.41 down to +6.16 just before quitting at 5:00am PDT.

There were no fireball class meteors seen this morning. As Paul Jones mentioned earlier, I also saw a lot of nice negative magnitude Perseids. A couple of these were distinctly orange or copper colored. A few were also yellow but no other colors were noticed. 

My overall impression of this Perseid peak was that it was slightly stronger than expected and would have been better appreciated had the moon not interfered. While a 25% illuminated waning moon has little effect on the Geminids, it does affect the Perseids as the moon is located close to the radiant. I also believe the moonlight is scattered more throughout the sky during the summer compared to the winter months. I thought my conditions were very transparent but out of curiosity, I shone my spotlight straight up only to discover that the sky was full of particles which created an intense beam of light. 

Details of my data will soon be posted to the Perseid profile on the IMO's website.

Robert Lunsford