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Photometric data by ChartID is OK!

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SGEO's picture
Photometric data by ChartID is OK!

I raised concerns at the recent SAS meeting that the AAVSO's VSP (Variable Star Plotter) chart/photometry system was not able to recover old data from VSD (the comp star database), that a chartID generated a year ago, if submitted to VSP today, might get back different magnitudes for the comp stars if those stars had been updated in the interim.

This is Not true; my assertion was incorrect. And I apologize for scaring you!

If you have a chartID of the new series (ie, prefixed with and X) you can be sure that VSP will always come back with the same report, the same values. I believe this chart scheme has been in place since 2008.

My assertion was based on a cursory analysis of the database structures where I was not able to spot the relationship of timestamp-to-chartID. The code for VSP and VSD is very difficult to understand. But a simple experimental check demonstrated that old chartID's work, fetching the same values they reported when they were created.

Sorry about the alarm.

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484