HW8: Aperture Photometry

AST 311 HW 8: Aperture Photometry

Joe Regan

11/6/15

Introduction

In September 2015, we went to Baker Observatory to take images of targets that we had chosen for that night. We used the 8-inch CPC telescopes and SBIG ST-I cameras to obtain darks, biases, and flats, along with images of our targets, Altair in my case, in order to reduce the target images and run aperture photometry code on them later. The code gave enough information to calculate the apparent magnitude of our targets using the instrumental magnitude, aperture size, and full-width at half-max, which was calculated to roughly 0.68.

Procedure
First, we obtained code from Dr. Plavchan through Exo used to determine the instrumental magnitude, aperture size, errors, and full width at half max. The code, when run on reduced images, determines that and the position of the star in the image. I ran the code on all ten of the reduced images I took of Altair, and used the ten given instrumental magnitudes to calculate the apparent magnitude of the star.

Results and Discussion
The instrumental magnitudes of the ten images of Altair range from 10.04 to 11.29 and the exposure time of the images was 0.5 seconds. The full width at half max of the images ranged from 220082 to 873073, and the aperture size on average was 4. Using this data, I determined that the apparent magnitude of Altair was roughly 0.68.

Fig. 1: Example reduced image of Altair, exposure time 0.5 seconds

After looking up the apparent magnitude of Altair, I found it to be 0.77, which is about 0.09 more than I calculated.