Review of the PEPObs web based tool for entry of raw PEP data has identified a time entry issue. Although the tool will allow the observer to specify a time base different than UTC, it does not correctly handle the calculations unless the time is entered as UTC. Currently there are no short term plans to update this legacy tool, so observers using PEPObs should convert their times of observation to UTC prior to entering the raw data in this tool. Besides the obvious issue of incorrectly logging the time of the measurement, this error also results in an incorrectly reduced magnitude since the time of observation and observer location is used to calculate the airmass used for the atmospheric extinction correction.
If you have used the tool with other than UTC times it will be necessary to delete the observation and re-enter the data with the correct time. I am currently working to determine how many observers/observations are affected, and to more fully understand the underlying program. I encourage comments on this forum from observers using this tool to aid in resolving this issue in the most efficient manner.
Jim.
I did several tests to attempt to troubleshoot this problem. I entered observations spaced a minute apart in Eastern Daylight Time and Eastern Standard Time. The program interpreted both times as Eastern Standard Time when it did the data reduction. I did not test other time zones, but I did enter a UTC observation at the same time as the EST observation and verified the results were the same. I am recommending that only UTC times be used with this software to avoid this issue.
If you want to verify observations you previously submitted, calculate the JD of the time of the middle variable star observation. This should agree with the JD in the AAVSO database. if this time is off by approximately 0.0417 days then your time zone was not reduced correctly, your airmass correction was not calculated correctly and you wil have to re-enter the data using UTC.
Please post any questions or concerns to this forum thread.
Jim