2024 February 12
We have discovered that a misconfigured maintenance operation run on November 18, 2023 caused the deletion of ~90% of the records from the DASCH lightcurve database. The problem was addressed on February 10, 2024 by the restoration of a backup copy of the database. If you requested DASCH lightcurve data at any time between these two dates, you should re-fetch the data.
Due to the way that the DASCH lightcurve database works, the effect of this mistake was to cause the data services to incorrectly report detections as upper limits, a manifestation of the Missing Lightcurve Points known issue. While this issue is known to still occur at times, hopefully it will be much less prevalent.
The backup database that was restored was one established before the 2023-2024 campaign to scan the large “A” plates. Photometry from A-plates scanned before today (February 12th) will be missing from the compiled lightcurve database for the time being. The intention is to rebuild the lightcurve database from scratch in the coming months, which will restore both these data and various missing measurements and other errors accumulated over the years.
2024 February 5
We have started developing a summary of the known issues in the current DASCH data. Although the team aspires to eliminate as many of these issues as possible, in a dataset like DASCH such efforts are literally never-ending. So, please review the summary early and often! Some of the known issues can have major impacts on the scientific results derived from DASCH data.
2024 January 30
We have added a new page, Citing & Acknowledging DASCH.
2023 December 12
Photographs of plate jackets and the plates themselves are once again publicly available. Note that the plate photos are digital camera images of the plates, not the detailed scans, and should not be used for science.
2023 December 7
The DASCH website — the thing you’re reading now — has been refreshed! For the time being, we are trying to minimize disruptions by keeping the look and feel close to the site’s historical styling. There are, however, some improvements and fixes under the hood, so you might see slightly different text and behavior in places. In particular, the default photometric catalog has returned to APASS, rather than ATLAS.
We have done our best to validate the changes but if you see anything that appears to be a bug, please reach out to the technical contact!
Expect to see more changes going forward as we strive to increase the usability and quality of the site. Noteworthy changes will be logged on this news page.
2023 November 9
Harvard College Observatory is delighted to announce that, after a thorough investigation and overhaul, DASCH systems are back online, and DASCH scanning has resumed. All DASCH scientific data products are once more accessible through the data access portal.
2023 August 23
Culminating a six-month process, the final backup tape of raw DASCH scan data has been duplicated onto Amazon AWS’s Glacier Deep Storage system, providing a new disaster recovery failsafe.