Format of Downloaded Data

Short letter from the AAVSO Director to colleagues using AAVSO data.

Data downloaded from our data download page in comma, tab or space-deliminated formats will adhere to the following guidelines. Data downloaded in VOTable format will adhere to the VOTable XML schema but the description of the fields will match what is below, in order.

1. JD: The Julian Date of the observation.
2. Magnitude: The magnitude estimate of the observation. A < sign means it was a null observation "fainter than" the magnitude given. A : (colon) means the observer was uncertain about the estimate.
3. Uncertainty: Uncertainty (error) of the observation as submitted by the observer
4. HQ Uncertainty: Uncertainty (error) of the observation as determined by AAVSO HQ
5. Band: Bandpass of the observation
6. Observer Code: This is a unique ID assigned to each observer.
7. Comment Code: Comment codes submitted by the observer. A list of codes is here.
8. Comp Star 1: The comparison star(s) used to make the visual estimate. If photometric, this is the comparison (C) star ID.
9. Comp Star 2: The comparison star(s) used to make the visual estimate. If photometric, this is the check (K) star ID.
10. Charts: The charts used to find the field and ID the stars
11. Comments: Comments on the observation, usually from the observer
12. Transform: If transformation coefficients were applied to the observation then this will be "Yes".
13. Airmass: The airmass of the observation.
14. Validation Flag: This flag describes the level of validation of the observation. G means the observation has passed our validation tests. D means that during the validation phase it was flagged discrepant and should be used with extreme caution. P means it has only undergone pre-validation, meaning it was checked for typos and data input errors only. No flag means it has not been validated at all and should be used with caution.
15. Cmag: Supplied magnitude of the comparison star
16. Kmag: Measured magnitude of the check star
17. HJD: Heliocentric Julian Date
18. Name: Name of the star

Note: The AAVSO database dates back to the 19th century. As a result, it changed over time and fields were added and removed. As a result, some of the fields may be empty in early observations.

Questions and requests should be submitted here.