Uploaded August 2017 | Updated September 2026, 2 weeks ago
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![AAVSO How to [Understand Star Photometry]](https://i.ytimg.com/vi/ufbFaUywEBg/mqdefault.jpg "AAVSO How to [Understand Star Photometry]
Originally broadcast March 5, 2022. Instructor: Richard Berry. Berry is well experienced in stellar photometry and was a programmer for the science-oriented software Astronomical Image Processing for Windows (AIP4Win).
Photometry seems like magic: you click on a star image and a magnitude pops up! But a lot happens between the moment you click and the moment that magnitude pops up on the computer screen. Berry explores with you in non-technical terms what the computer has to do to turn your pixels into meaningful information. This talk complements Bob Buchheims Introduction to Photometry 2021 webinar (https://www.youtube.com/watch?v=gcE7c4CggFM). Berry describes how to do photometry by presenting the inside picture of how photometry works and why it works so well. He demonstrates using AIP4Win software (join aip4win@groups.io to download this freeware package), but all stellar photometry software works pretty much the same way.
Interested in AAVSOs Instrumentation & Equipment Section led by Rich Berry? aavso.org/instrumentation-section
Interested in our other How-to Hours and webinars? aavso.org/programs-events
Visit us and learn how to make a meaningful contribution to science at aavso.org")
![AAVSO How to [Think About Transformation]](https://i.ytimg.com/vi/urgkBDkiUEE/mqdefault.jpg "AAVSO How to [Think About Transformation]
with instructor Tom Calderwood. Originally broadcast June 4, 2022. Astronomers have spent decades defining photometric systems. Systems like Johnson-Cousins define a standard scale on which photometry from different observers can be directly compared. However, simply using a Johnson or Cousins filter does *not* put your magnitudes on the standard system. Your data require adjustment, and this step is known as transformation. In this discussion, Tom explains why transformations are necessary, and sketch out the basics of how their parameters are determined.
Tom Calderwood is head of the AAVSO Photoelectric Photometry Observing Section. He observes from Central Oregon, and is the author of The Great Dimming of Betelgeuse in the March 2021 issue of Sky & Telescope. A graduate of MIT in mathematics, he is a retired software engineer who worked on parallel processing computers, communication networks, video games, and the data system for the Chandra X-ray Observatory.
Interested in attending a free live How to [...] session? aavso.org/2022-how-to-hours
Want to learn more about photoelectric photometry (PEP)? AAVSO has an observing section full of people dedicated to it: https://www.aavso.org/aavso-photoelectric-photometry-pep-section
Check out all AAVSO has to offer you at aavso.org")
