Format of the Data File

  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.
  3. Uncertainty: Uncertainty (error) of the observation as submitted by the observer
  4. HQuncertainty: Uncertainty (error) of the observation as calculated by AAVSO Headquarters
  5. Band: Bandpass of the observation. The allowable filters are listed here. [For data requests filled by HQ staff under special circumstances, the number corresponding to each band is given here].
  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 locate the comparison stars and their values. As of July, 2008 new charts were issued with a Chart ID format of XXXXY where XXXX is a number and Y can be any combination of letters. You can visit our Variable Star Plotter and type in that Chart ID to see the exact chart the observer used to make that observation. For Chart IDs that are not in that format, contact AAVSO HQ and we can e-mail you a copy of the chart used in the observation.
  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.
    • V means the observation has passed our validation tests.
    • T means that during the validation phase it was flagged discrepant and should be used with extreme caution.
    • Z means it has only undergone pre-validation, meaning it was checked for typos and data input errors only.
    • U 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
  19. Affiliation: Organization affiliated with the observer that took this data.  See this link for a list of affiliation codes and their corresponding Organizations.
  20. Magnitude Type: This field describes the kind of magnitude used in the observation:
    STD - standardized magnitude.
    DIFF - differential magnitude. The value of Comp Star 1 is needed to compute the standard magnitude.
    STEP - un-reduced step magnitude. These magnitudes are given as 0.0 and the step sequence may be found in the Comment Code field.
  21. Group: Denotes what group of filters were used for this observation.
  22. ADS Reference: The article identifier in CDS/ADS Bibliographic Code format
  23. Digitizer: The digitizer code for the individual who digitized and submitted the data (identical to the individual's observer code if they are already an AAVSO observer).
  24. Credit: Organization to be credited for the observation.

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.