Project News

2024 May 2

Thanks to work from GAVO and Markus Demleitner in particular, DASCH data are now accessible in the Virtual Observatory (VO) data network!

See the GAVO blog post for details. While DASCH’s “Cannon” data services have long made certain data tables available in the VOTable format, it hasn’t been possible to query the DASCH databases using VO standard protocols, preventing DASCH data from fully integrating into the VO ecosystem of tools and services. Now, the DASCH plate metadata are available as an ObsCore table and SIAP2 service hosted by GAVO. This means that tools like Aladin will automatically start including DASCH plates in their results when users search the sky for images covering a region of interest. Thanks to an integration with the data services provided by the new StarGlass service, it's also possible to download DASCH FITS files through VO-standard mechanisms, too. See the blog for worked examples of all this!

This VO service relies on a copy of DASCH’s plate database that's hosted by GAVO. At the moment, we expect to periodically update this copy as DASCH data (re)processing occurs. In the future, it may make sense to transition to hosting DASCH-related VO services directly on the StarGlass infrastructure.

Big thanks to Markus for all of his work to provide this new integration!

2024 March 28

Today, the final plates in the DASCH sample were scanned, marking an enduring milestone in the history of the Plate Stacks. It would not have been possible to reach this point without the tireless effort of the hundreds of people who contributed to the DASCH project over the past two decades.

While the completion of the scanning effort marks the end of a chapter, it is far from the end of the story. In the proximate future, the team will be busy with a variety of efforts including:

  1. Completing the next formal scientific data release, scheduled for later this year.
  2. Enhancing the new StarGlass website, in conjunction with Project PHaEDRA.
  3. Securing resources to digitize the remainder of the Plate Stacks holdings, which include more than 100,000 glass plate photographs of the sun, moon, eclipses, and Annie Jump Cannon's spectral data, as well as photographic film, printed materials, and other artifacts.
  4. Exploring opportunities to digitize other glass plate collections using the DASCH scanner.

Resources permitting, subsequent data releases will streadily refine the DASCH analysis, tooling, and documentation. With over 400 terabytes of imaging data across a very heterogeneous collection, there are nearly endless opportunities to do so.

2024 March 13

Harvard College Observatory is delighted to unveil StarGlass, a new website for exploring the HCO Astronomical Photograph Glass Plate Collection.

StarGlass lets you interrogate a comprehensive database documenting all of the plates in the HCO collection, the handwritten notebooks describing their acquisition and analysis, and the people involved in that work. For less-analytical use cases, StarGlass should provide a way to explore the HCO plate collection that is much cleaner and more user-friendly than the existing DASCH “Cannon” data access website.

StarGlass does not replace the DASCH Cannon website for access to DASCH lightcurve data and structured data products. StarGlass does, however, provide access to plate-level products. In particular, for the first time StarGlass allows you to download DASCH’s full-plate mosaic FITS files, restricted only by API rate limits. (Open up the “Plate Details” for a plate of interest, click on the “Mosaics” tab, and click one of the arrow-into-box download icons.) Furthermore, StarGlass provides an API for programmatic queries and data retrieval. If you sign up for a StarGlass user account, you can obtain an API key allowing you to make requests, including mosaic retrievals, with much higher rate limits than are allowed for anonymous clients.

StarGlass is still being beta-tested. Please use the feedback form to tell us about your experience!

2024 March 6

The DASCH data access servers have had intermittent periods of poor performance in the past few weeks. This issue should now be largely solved. If you experience queries that fail with an error or take more than ~5 minutes to complete, please contact Peter Williams with information about what you were doing.

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.

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