The Delta Aquariids (SDA’s) are the strongest southern shower active during the northern hemisphere’s summer months. The Earth encounters these particles from July 21 through August 23 with a broad maximum occurring near July 30. Zenith hourly rates (ZHR’s) average 20 near maximum activity. During July and August this radiant is well placed as it rises near 2200 local daylight time and culminates at 0300 LDT. This shower is visible over most of the Earth but those observers located in the southern tropical areas are best suited as the radiant passes through their zenith. Observers further south may have a lesser zenith angle but they also enjoy a longer night which allows longer observation of this activity.
On July 30, the radiant is located at 22:42 (340) -16. The area of the sky is located in southern Aquarius, three degrees west of the 3rd magnitude star Delta Aquarii. An easier signpost may be the bright first magnitude star Fomalhaut (Alpha Pisces Austrinis), which lies fifteen degrees to the southeast of the SDA radiant. These meteors strike the Earth’s atmosphere with a velocity of 42 kilometers per second. Visually these meteors would appear to possess a medium speed for those shower members seen far from the radiant and high in the sky. Those seen close to the radiant or close to the horizon would appear to move slower. Most members of this shower are faint so rates seen from urban locations would most likely be unimpressive. Only from darker rural locations can this shower really be appreciated.
To view this shower it is advised that you limit your session to the morning hours when the radiant has achieved sufficient altitude. The best rates will occur near 0300 LDT when the radiant lies highest in the sky. You should face toward the southern half of the sky so that you may be able to better distinguish the SDA’s from the other weaker radiants active in this same general portion of the sky. Facing this direction will also allow you to experience the swift Perseids shooting into your field of view from behind. Although not as numerous as the SDA’s in July, the Perseids will provide some memorable bright meteors as you patiently wait for the fainter Aquariids to appear. In late July the moon will be a thin crescent phase and will not interfere with viewing the SDA’s.
While the Perseids provide more activity, their rates will be tempered by a bright moon in August. The Southern Delta Aquariids will provide a good show in impressive dark skies so make it a point to try to view this activity. If you are unable to view on the morning of the 30th, rates will still be good for a few nights before and after this date. Be sure to share your observations with the ALPO Meteors Section!