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SkyProbe Data AccessIn December 2023, direct, queryable, access to the SkyProbe data archive was discontinued as a result of changes to CFHT's computing infrastructure and security policies. This has been replaced with downloadable CSV files which contain blocks of historical SkyProbe data, and public access to live SkyProbe data, which can be used to construct external data repositories. Current Raw DataThe CFHT public weather server has SkyProbe data available. The data published on the public weather server is the "latest value" and automatically updates as new data come in. Data from SkyProbe is created once per minute (60-second intervals). CFHT recommends that users who desire an updating display of real-time SkyProbe values during nighttime operations, should setup an automatic query or webscraper on weather server page, querying once per minute for the latest SkyProbe data. Link to the CFHT Public Weather Server SkyProbe data is listed at the bottom of the weather server page in five separate fields:
Current SkyProbe data is only available when CFHT is open and performing science operations. When not operating, the weather server page will display "invalid" in these fields. Sample data, as displayed on the weather server page during science operations:
SkyprobeTime = 2024/02/13,07:42:53 # Time of last SkyProbe Update (GMT) As an example:
This data is unfiltered, and may contain erroneous or spurious data points. Additionally, there is a small, but variable, zero-point offset to the extinction measurement. This varies based on sky conditions, instrument cleanliness (dust on the lens), and telescope airmass. For simplicity's sake, CFHT staff usually assume an average offset of +0.03. Using this assumption, the "true" value for the extinction measurement displayed above would be 0.0430. Historical Raw DataSelect the desired year or semester below to download a CSV file that contains the SkyProbe data from that period. Data from the current year will be added in early January of the following year. Semester data is added after each semester*. Data prior to 2010 is not available in this format. Contact the CFHT QSO Team if you have questions. For visualized plots by night, use the Historical Graph Tool. These plots go back to 2001. Each full year file is approximately 10MB. Semester files are approximately 5MB.
*'A' semesters run from February 1 to July 31. Data will be added in early August. 'B' semesters run from August 1 to January 31 of the following year. Data will be added in early February. As is standard in CSV files, this data is provided as a list of comma-separated elements, with each row being an individual SkyProbe archival record. There are six elements per row. They are:
Sample data, as listed in the CSV files:
2020-08-06.03:00:07,"2020/08/06, 12:59:57",0.0870,0.0070,1.1890,405 Using the top row as an example:
This data is unfiltered, and may contain erroneous or spurious data points. Additionally, there is a small, but variable, zero-point offset to the extinction measurement. This varies based on sky conditions, instrument cleanliness (dust on the lens), and telescope airmass. For simplicity's sake, CFHT staff usually assume an average offset of +0.03. Using this assumption, the "true" value for the extinction measurement displayed above would be 0.0570. Note that there are gaps in the data (reasons will vary). Contact the QSO Team if you have further questions. |