![AAVSO How to [Think About Transformation] @AAVSOHQ](https://i.ytimg.com/vi/urgkBDkiUEE/maxresdefault.jpg)
Uploaded June 2022 | Updated September 2026, 2 weeks ago
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: aavso.org/aavso-photoelectric-photometry-pep-section
Check out all AAVSO has to offer you at aavso.org
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: aavso.org/aavso-photoelectric-photometry-pep-section
Check out all AAVSO has to offer you 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")
