August 1, 2014.
Photometry is the measure of the brightness of an object. When making such measurements on stars, it is done is units of magnitude, which is on a logarithmic scale with a base of ~2.512. Variable star photometry using a commercially available digital camera is not going to be as accurate and precise as equipment used by astronomers, and because of the logarithmic scale of magnitude used, determining how much of an effect different error reduction strategies have is not straightforward, and is best done experimentally.
My research is conducting photometry on variable stars (changing brightness) with a digital camera, and testing both the limits in terms of how faint of a star can be reliably detected, but also which methods for recording and processing data have an effect on the measurement in the first four digits of a photometric measurement. Examples include whether taking dark frames, in which a picture of darkness is taken with the same camera setting as the night sky image, and subtracted from the first image to reduce in-camera noise, has an effect, and if so, how many dark frames before no significant change is seen. Other error reduction strategies I’m examining include accounting for the drop off in brightness towards the edges of an image due to camera optics, canceling out the brightness of the sky to correct for light pollution, and calibrating the target star against other known stars.
Instrumentation | Optics | Stars, Interstellar Medium and the Galaxy
Robert T. Sparks
National Optical Astronomy Observatory (NOAO)
This material is based upon work supported by the S.D. Bechtel, Jr. Foundation and by the National Science Foundation under Grant No. 0952013. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the S.D. Bechtel, Jr. Foundation or the National Science Foundation. This project has also been made possible with support of the National Marine Sanctuary Foundation. The STAR program is administered by the Cal Poly Center for Excellence in Science and Mathematics Education (CESaME) on behalf of the California State University (CSU).