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AAVSO’s Annual Campaign

Donate Now to Support Variable Star Education.

https://www.aavso.org/donate-now

They Might Be Hypergiants

AAVSO data has helped unveil the mysteries of Rho Cas and stars like it.

https://www.aavso.org/blog/they-might-be-hypergiants

A Universe of Opportunity: The Future of Small Telescope Science in the LSST Era

Each time a major sky survey comes online, the inevitable question arises: “Is this the end of amateur astronomy?”

https://www.aavso.org/blog/future-of-small-telescope-science

Discover the AAVSO

An international community

Welcome to the conversation.

We are excited to announce a transition to a new forum system. The new system is modern, faster, and easier-to-use.

https://forums.aavso.org/

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The mission of the AAVSO is to enable anyone, anywhere to participate in scientific discovery through variable star astronomy.

Resources

(VSX) Variable Star Index

jaavso

The Journal of the AAVSO

Data

Submit and Access Data

Telescope

Tools and Observer Resources

Observing Sections

Observing Sections

/observing-sections

Education

Education

CHOICE Courses, Manuals, Videos

AAVSO In the Press

AAVSO In the Press

Membership and Support

The AAVSO is an equal opportunity and discrimination / harassment free environment.
Please read our policies HERE

AAVSO at a Glance

Variable Star Observations in Database:

7 8 , 3 7 4 , 3 3 7 and Counting ...

Last Observation Received:

46 min 17 sec ago by JAHB - Ahmad Jabbarian (DE)

HAT-P-20 Dec 20.5297 11.1837V

Plot HAT-P-20 light curve

JAAVSO Volume 53, Number 2, December 2025, print version now available

Dec 17

JAAVSO Volume 53 Number 2, 2025 is published

Dec 15

Director’s Report for 2025-Q2

Dec 2

New User Profiles, Settings, and Search

Oct 22

New Data Usage Guidelines

Oct 7

Our Stellar Partners

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$Diffraction Limited logo of a swirled circle with text: Diffraction: Astronomy + Scientific Imaging SolutionsIm$

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Text reads "Sky & Telescope" with the ampersand in a circle.