Meteor Activity Outlook for July 19-25, 2008

After several months of low activity the meteor rates for both hemispheres see a marked increase in July. In the northern hemisphere the change is not noticeable until mid-month when several southern radiants, the Perseids, and sporadic rates all increase in activity. Southern rates are good all month long.

During this period the moon reaches its last quarter phase on Friday July 25. At this time the moon will rise near 0100 local daylight time (LDT) and will be in the sky the remainder of the morning. This weekend and early next week the intense moonlight will obscure all but the brightest meteors making observations difficult. The estimated total hourly rates for evening observers this week is near two for those located in the mid-northern hemisphere (45 N) and three for those viewing from the mid-southern hemisphere (45 S). For morning observers the estimated total hourly rates should be near ten for those located in the mid-northern hemisphere (45 N) and fifteen for those viewing from the mid-southern hemisphere (45 S). These rates assume that you are watching from rural areas away from all sources of light pollution. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Rates are reduced this week due to intense moonlight.

The radiant positions and rates listed below are exact for Saturday night/Sunday morning July 19/20. These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky. A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies at the edge and not the center. Viewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.

The full descriptions of each active meteor shower will continue next week when the moon becomes less of a nuisance to observers.

The table below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.