Nonprofit · EIN 04-2164402
AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
Tax-exempt · CAMBRIDGE, MA 02140
Financials
| Year ended | Form | Revenue | Expenses | Net income | Total assets | Liabilities | Net assets |
|---|---|---|---|---|---|---|---|
| September 30, 2025 | 990 | $1,682,737 | $1,276,217 | $406,520 | $20,337,952 | $281,518 | $20,056,434 |
| September 30, 2024 | 990 | $1,074,729 | $1,216,226 | -$141,497 | $19,079,368 | $385,998 | $18,693,370 |
| September 30, 2023 | 990 | $691,694 | $1,194,983 | -$503,289 | $16,088,028 | $420,023 | $15,668,005 |
Financial details: 990 for the year ended September 30, 2025
Revenue
- Contributions, gifts and grants
- $366,182
- Program service revenue
- $156,899
- Investment income
- $1,159,656
- Net gain from sales of assets
- $767,421
- Other revenue
- $0
Expenses
- Grants and similar amounts paid
- $0
- Compensation of officers, directors and key employees
- $223,413
- Other salaries and wages
- $479,728
- Salaries, compensation and benefits (total)
- $836,961
- Professional fundraising fees
- $0
- Legal fees
- $3,259
- Accounting fees
- $49,645
- Occupancy
- $90,913
- Travel
- $17,410
- Depreciation
- $9,525
- Program services (functional)
- $771,146
- Management and general (functional)
- $371,139
- Fundraising (functional)
- $133,932
Balance sheet and other
- Total assets, start of year
- $19,079,368
- Total assets, end of year
- $20,337,952
- Total liabilities, end of year
- $281,518
- Net assets, end of year
- $20,056,434
- Land, buildings and equipment
- $12,159
- Publicly traded securities
- $18,996,986
- Net assets without donor restrictions
- $16,369,987
- Net assets with donor restrictions
- $3,686,447
- Gross receipts
- $5,420,584
- Employees
- 8
- Volunteers
- 785
- Year formed
- 1911
- State of legal domicile
- MA
From the e-filed returns the IRS publishes as XML (latest three processing years; amended returns replace the original). PDF copies at the IRS.
Officers, directors and key employees
As listed on the 990 for the year ended September 30, 2025, highest compensation first.
| Name | Title | Hours / week | Compensation | Other / benefits |
|---|---|---|---|---|
| DR BRIAN KLOPPENBORG | EXECUTIVE DIRECTOR Trustee or director, Officer | 38 | $190,972 | $20,932 |
| RICHARD BERRY | PRESIDENT Trustee or director, Officer | 2 | $0 | $0 |
| ROBERT STEPHENS | TREASURER Trustee or director, Officer | 3.5 | $0 | $0 |
| DIOGO TEIXEIRA | DIRECTOR Trustee or director | 1 | $0 | $0 |
| THOMAS MACCARONE | DIRECTOR Trustee or director | 1 | $0 | $0 |
| PETER BEALO | DIRECTOR Trustee or director | 1 | $0 | $0 |
| ARNE HENDON | SECRETARY Trustee or director, Officer | 1 | $0 | $0 |
| WALT COONEY | VP1 Trustee or director, Officer | 1.5 | $0 | $0 |
| MARK MUNKACY | VP2 Trustee or director, Officer | 1 | $0 | $0 |
| MATT CRAIG | DIRECTOR Trustee or director | 1 | $0 | $0 |
| AARON SLISKI | DIRECTOR Trustee or director | 1 | $0 | $0 |
| DIPANKAR MAITRA | DIRECTOR Trustee or director | 1 | $0 | $0 |
| BRUCE MCMATH | DIRECTOR Trustee or director | 1.5 | $0 | $0 |
| MARK HARDAKER | DIRECTOR Trustee or director | 1 | $0 | $0 |
| MOLLY WAKELING | DIRECTOR Trustee or director | 1 | $0 | $0 |
990 for the year ended September 30, 2024: 16 people
| Name | Title | Hours / week | Compensation | Other / benefits |
|---|---|---|---|---|
| DR BRIAN KLOPPENBORG | EXECUTIVE DIRECTOR Trustee or director, Officer | 35 | $182,132 | $19,663 |
| RICHARD BERRY | PRESIDENT Trustee or director, Officer | 6 | $0 | $0 |
| SARAH AUSTRIN WILLIS | VICE PRESIDENT Trustee or director, Officer | 2 | $0 | $0 |
| DENNIS CONTI | 2ND VICE PRESIDENT Trustee or director, Officer | 1 | $0 | $0 |
| ROBERT STEPHENS | TREASURER Trustee or director, Officer | 3 | $0 | $0 |
| KRIS LARSEN | SECRETARY Trustee or director, Officer | 1 | $0 | $0 |
| DAVID COWALL | PAST PRESIDENT Trustee or director | 1 | $0 | $0 |
| DIOGO TEIXEIRA | DIRECTOR Trustee or director | 1 | $0 | $0 |
| ERIC HINTZ | DIRECTOR Trustee or director | 1 | $0 | $0 |
| THOMAS MACCARONE | DIRECTOR Trustee or director | 1 | $0 | $0 |
| PETER BEALO | DIRECTOR Trustee or director | 3 | $0 | $0 |
| PAT BOYCE | DIRECTOR Trustee or director | 1 | $0 | $0 |
| ARNE HENDON | DIRECTOR Trustee or director | 1 | $0 | $0 |
| WALT COONEY | DIRECTOR Trustee or director | 3 | $0 | $0 |
| MARK MUNKACSY | DIRECTOR Trustee or director | 1 | $0 | $0 |
| MATT CRAIG | DIRECTOR Trustee or director | 1 | $0 | $0 |
990 for the year ended September 30, 2023: 17 people
| Name | Title | Hours / week | Compensation | Other / benefits |
|---|---|---|---|---|
| KATHLEEN SPIRER | OPERATIONS MANAGER Highest-paid employee | 35 | $107,246 | $16,847 |
| DR BRIAN KLOPPENBORG | EXECUTIVE DIRECTOR Officer | 35 | $45,769 | $13,248 |
| DAVID COWALL | PRESIDENT Trustee or director, Officer | 1 | $0 | $0 |
| RICHARD BERRY | 1ST VICE PRESIDENT Trustee or director, Officer | 1 | $0 | $0 |
| KRISTINE LARSEN | SECRETARY Trustee or director, Officer | 1 | $0 | $0 |
| ROBERT STEPHENS | TREASURER Trustee or director, Officer | 1 | $0 | $0 |
| SARAH AUSTRIN WILLIS | 2ND VICE PRESIDENT Trustee or director, Officer | 1 | $0 | $0 |
| ROBERT BUCHEIM | COUNCIL MEMBER (TERM EXPIRED 9/2023) Trustee or director | 1 | $0 | $0 |
| KEN HUDSON | COUNCIL MEMBER Trustee or director | 1 | $0 | $0 |
| THOMAS MACCARONE | COUNCIL MEMBER Trustee or director | 1 | $0 | $0 |
| MARTINA BELZ ARNDT | COUNCIL MEMBER (RESIGNED 4/2023) Trustee or director | 1 | $0 | $0 |
| DENNIS CONTI | COUNCIL MEMBER Trustee or director, Officer | 1 | $0 | $0 |
| DR JOYCE A GUZIK | COUNCIL MEMBER (TERM EXPIRED 10/2022) Trustee or director | 1 | $0 | $0 |
| ANTONELLA NOTA | COUNCIL MEMBER (RESIGNED 5/2023) Trustee or director | 1 | $0 | $0 |
| PETER BEALO | COUNCIL MEMBER (APPOINTED 11/2022) Trustee or director | 1 | $0 | $0 |
| PATRICK BOYCE | COUNCIL MEMBER (APPOINTED 11/2022) Trustee or director | 1 | $0 | $0 |
| ARNE HENDEN | COUNCIL MEMBER (APPOINTED 11/2022) Trustee or director | 1 | $0 | $0 |
Address and contacts
- Address (IRS master file)
- 1770 MASSACHUSETTS AVE STE 121, CAMBRIDGE, MA 02140-2808
- In care of
- % DR BRIAN KLOPPENBORG
- Principal officer (990 for 2024)
- BRIAN KLOPPENBORG, 1770 MASSACHUSETTS AVE, CAMBRIDGE, MA 02138
- Signed the 990
- BRIAN KLOPPENBORG, EXECUTIVE DIRECTOR
- Phone
- (617) 354-0484
- Website
- WWW.AAVSO.ORG
- Return prepared by
- DOEREN MAYHEW
Mission
THE AAVSO, THROUGH ITS MEMBERS AND THE BROADER ASTRONOMICAL COMMUNITY, CONDUCTS ASTRONOMICAL RESEARCH, DOES DATA COLLECTION, MAINTAINS A DATABASE OF KNOWN VARIABLE STARS, A DATABASE OF INDIVIDUAL OBSERVATIONS MEASURING BRIGHT OF STARS IN VARIOUS COLORS, A DATABASE OF EXOPLANET OBSERVATIONS, A DATABASE OF SUNSPOT COUNTS, AND A DATABASE OF SPECTROGRAPHS. THE AAVSO HAS ABOUT 1,400 MEMBERS, THE MAJORITY OF WHICH CONTRIBUTE ASTRONOMICAL OBSERVATIONS. THE VARIABLE STAR DATABASE HAS 2 MILLION KNOWN VARIABLE STARS. THERE ARE ABOUT 65 MILLION BRIGHTNESS OBSERVATIONS, 8 THOUSAND EXO-PLANET TRANSITS, 15 THOUSAND SPECTRA, AND 181 THOUSAND SOLAR OBSERVATIONS. THE AAVSO ORGANIZES OBSERVING CAMPAIGNS OR PROVIDES A PLATFORM FOR PROFESSIONAL ASTRONOMERS TO REQUEST MONITORING OF STARS FOR SPACECRAFT MISSIONS. THE AAVSO HAS ABOUT 30 OF THESE CAMPAIGNS EACH YEAR. THE OBSERVATIONS AND DATABASES ARE CITED IN ABOUT 300 RESEARCH ARTICLES EACH YEAR.
Program accomplishments
- THE AAVSO, THROUGH ITS MEMBERS AND THE BROADER ASTRONOMICAL COMMUNITY, CONDUCTS ASTRONOMICAL RESEARCH, DOES DATA COLLECTION, MAINTAINS A DATABASE OF KNOWN VARIABLE STARS, A DATABASE OF INDIVIDUAL OBSERVATIONS MEASURING BRIGHT OF STARS IN VARIOUS COLORS, A DATABASE OF EXOPLANET OBSERVATIONS, A DATABASE OF SUNSPOT COUNTS, AND A DATABASE OF SPECTROGRAPHS. THE AAVSO HAS ABOUT 1,200 MEMBERS, THE MAJORITY OF WHICH CONTRIBUTE ASTRONOMICAL OBSERVATIONS. THE VARIABLE STAR DATABASE HAS ALMOST 11 MILLION KNOWN VARIABLE STARS. THERE ARE ABOUT 74 MILLION BRIGHTNESS OBSERVATIONS, 14 THOUSAND EXO-PLANET TRANSITS, 18 THOUSAND SPECTRA, AND 292 THOUSAND SOLAR OBSERVATIONS. THE AAVSO ORGANIZES OBSERVING CAMPAIGNS OR PROVIDES A PLATFORM FOR PROFESSIONAL ASTRONOMERS TO REQUEST MONITORING OF STARS FOR SPACECRAFT MISSIONS. THE AAVSO HAS ABOUT 30 OF THESE CAMPAIGNS EACH YEAR. THE OBSERVATIONS AND DATABASES ARE CITED IN ABOUT 300 RESEARCH ARTICLES EACH YEAR.Expenses $360,565 · revenue $72,359
- THE AAVSO HOLDS AN ANNUAL SCIENCE AND MEMBERSHIP MEETING EACH FALL. THE MEETING ROTATES THROUGHOUT THE COUNTRY TO GIVE MEMBERS A BETTER CHANCE TO PARTICIPATE. EACH MEETING HAS ABOUT 75 IN-PERSON PARTICIPANTS AND AN ADDITIONAL 25-50 ONLINE MEMBERS. THE MEETINGS ARE OFTEN HELD IN CONJUNCTION WITH A SPECIAL INTEREST WORKSHOP BEFORE OR AFTER THE MEETING. THE MEETING WILL HAVE 1-1/2 DAYS OF SCIENCE TALKS, INCLUDING RESEARCH PRESENTATIONS BY MEMBERS. THERE IS ALSO A RECEPTION, FINAL DINNER, AND A HALF-DAY MEMBERSHIP MEETING WHERE FINANCIAL AND OPERATIONAL RESULTS ARE PRESENTED, AND AWARDS PRESENTED. AND THE INCOMING BOARD OF DIRECTORS IS VOTED UPON.Expenses $213,656 · revenue $53,516
- THE AAVSO PROVIDES SEVERAL EDUCATIONAL COURSES, WEBINARS, MENTORING, ARTICLES, BLOG POSTS, AND OTHER COMMUNICATIONS. WE OPERATE AN ONLINE FORUM ON MANY OBSERVING AND EQUIPMENT TOPICS. WE OPERATE A MENTORING PROGRAM FOR NEW OBSERVERS WHERE AN EXPERIENCED OBSERVER COACHES THEM. WE RECEIVE ABOUT 30 MENTORING REQUESTS PER YEAR. WE ALSO PROVIDE CHOICE COURSES, AND A MULTI-DAY EDUCATIONAL COURSE WHICH HAS ABOUT 100 PARTICIPANTS PER YEAR. EACH MONTH WE PROVIDE ZOOM WEBINARS ON VARIOUS SUBJECTS WHICH HAVE ABOUT 2,000 PARTICIPANTS EACH YEAR. WE ALSO POST WEBINARS TO OUR YOUTUBE CHANNEL GETTING OVER 4,000 VIEWS. WE ALSO POST ARTICLES ON VARIOUS SOCIAL MEDIA SITES AND ARE A RESOURCE FOR THE NEWS MEDIA CONCERNING STAR RESEARCH..Expenses $196,925 · revenue $31,024
What it must file and when
IRS records say it files Form 990 or 990-EZ. Based on its last return; a smaller organization may file the 990-N. Its accounting year ends in September, so each return is due on the 15th day of the 5th month after that.
| Tax year | Year ended | Due | IRS public records |
|---|---|---|---|
| 2025 | September 30, 2026 | February 16, 2027 | Not due yet |
| 2024 | September 30, 2025 | February 17, 2026 | 990 on file |
| 2023 | September 30, 2024 | February 18, 2025 | 990 on file |
IRS record
- EIN
- 04-2164402
- Tax-exempt status
- 501(c)(3): Charitable, religious, educational or scientific organization
- Foundation status
- Publicly supported organization (170(b)(1)(A)(vi))
- Donations deductible (Pub 78)
- Public charity, 50% deduction limit
- Exempt since
- 1954
- Accounting year ends
- September
- Files
- Form 990 or 990-EZ
- Category (NTEE)
- Science and technology (U310)
- Assets (IRS master file)
- $20,337,952
- Income (IRS master file)
- $5,420,584
Filing history
| Form | Year ended | Revenue | Expenses | Assets | Return |
|---|---|---|---|---|---|
| 990 | September 2025 | $1,682,737 | $1,276,217 | $20,337,952 | XML |
| 990 | September 2024 | $1,074,729 | $1,216,226 | $19,079,368 | XML |
| 990 | September 2023 | $691,694 | $1,194,983 | $16,088,028 | XML |
| 990 | September 2022 | $2,634,853 | $1,034,647 | $15,233,992 | IRS |
| 990 | September 2021 | – | – | – | IRS |
| 990 | September 2020 | – | – | – | IRS |
| 990 | September 2019 | – | – | – | IRS |
| 990 | September 2018 | – | – | – | IRS |
990-N: the IRS bulk file holds only the latest e-Postcard per organization; earlier years come from archived copies of that file since 2020 and can have gaps (the IRS e-Postcard search lists every one). 990, 990-EZ, 990-PF, 990-T: every e-filed return in the IRS e-file index since 2019; XML for the latest three processing years, amounts from the IRS Statistics of Income extracts before that. PDF copies and determination letters at the IRS (search EIN 04-2164402).
Questions about AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
- What is the EIN of AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS?
- The employer identification number (EIN) of AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS is 04-2164402.
- Is AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS tax-exempt?
- Yes. The IRS lists it as tax-exempt under section 501(c)(3) since 1954.
- Are donations to AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS tax-deductible?
- Yes. It is listed in IRS Publication 78 (Public charity, 50% deduction limit).
- Which annual return does AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS file?
- Form 990 or 990-EZ. Based on its last return; a smaller organization may file the 990-N.
- When is the next return of AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS due?
- The return for tax year 2025 (the year ending September 30, 2026) is due February 16, 2027. Form 8868 extends it by six months; the 990-N cannot be extended.
- When did AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS last file with the IRS?
- The latest return in the IRS public files is the 990 for the year ended September 2025.
- Who is the principal officer of AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS?
- The 990 for the year ended September 30, 2025 names BRIAN KLOPPENBORG.
- Who are the officers and directors of AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS?
- The 990 for the year ended September 30, 2025 lists 15 people; 1 received compensation from the organization, the highest $190,972 (DR BRIAN KLOPPENBORG, EXECUTIVE DIRECTOR).
- How much revenue does AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS have?
- On its 990 for the year ended September 30, 2025 it reported revenue of $1,682,737, expenses of $1,276,217 and total assets of $20,337,952 at year end.
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