1. Analysis of background Perseid meteors using aperture photometry Abstract:The purpose of this project was to analyse background Perseids between 27th July and 11th August (a day before the peak prediction for this year of 12th August) for characteristics of the meteors such as the duration compared to the magnitude, and the population index of the shower. The meteors were recorded using three cameras recently installed at Armagh Observatory which monitor the sky to the north east, north west and south east respectively. The image to the left shows a stacked set of frames from a video clip. The visible constellations are named and the Perseid meteor can be seen in the middle of Cepheus, having come from the direction of Cassiopeia. The star map above shows the area of sky monitored by the meteor cameras. Perseids appear to emanate from the constellation Perseus located to the left of the centre of the map. Methodology:The cameras record meteors indiscriminately, so the Perseid video clips first had to be separated from other meteors. This was done by using the program XEphem which shows the positions of the stars in the camera’s view for any date and time, in conjunction with the video clips. By identifying the stars visible, the meteor’s path can be extrapolated back and checked to see if it comes from the direction of Perseus. Results: The next step was to analyse each Perseid individually.The maximum magnitude of each meteor was found by estimating the frames in which the meteor appeared brightest by eye and then using the program Gaia to calculate the signal from the meteor in each clip more precisely through aperture photometry. This works by calculating the signal (or amount of light) from the meteor minus background light using pixel counts. Meteor duration against maximum magnitude There is a formula linking the difference in magnitude of any two objects to the ratio of their brightness: m2 – m1 = 2.5log (B1/B2) where B1 and B2 are the brightnesses of the two objects and (m2 – m1) is the difference in their magnitudes. This formula arises from the fact that if two objects are one whole magnitude apart, the brighter object is 2.5 times brighter than the other. The formula converts the relative brightness into a difference in magnitude between the meteor and a star which can then be added to or subtracted from the magnitude of the star to find that of the meteor. Maximum magnitude against the point in the duration when the meteor reached maximum magnitude • Conclusions: • The bigger a meteor is, the longer it lasts • Larger meteors take longer to reach their maximum magnitude • The population index for the sample was 3.7, indicating that the meteoroids were relatively young • BANGORCAM is more sensitive than SECAM and NWCAM – it recorded more and fainter meteors Dawn Scott Hunterhouse College, Belfast Meteor magnitude distribution