You can obtain DASCH data through several different channels: daschlab, StarGlass, and the “Cannon” data portal.
At this time, the DASCH data are not versioned by data release. In other words, repeating the same query may yield different results as the DASCH data evolve. The DRnext overview page provides a best-effort summary of what is currently being distributed. See in particular the summary of known issues.
If you make use of DASCH data in scholarly work, you should properly cite and acknowledge DASCH.
daschlab
The DASCH team is introducing a new system for accessing and analyzing DASCH data: a Python toolkit called daschlab. Cloud-based notebooks allow you to perform basic data retrievals and analysis with minimal need to understand Python and no required software installation. See the DRnext: Getting Started section to, well, get started.
daschlab will eventually become the recommended framework for retrieval and analysis of DASCH astronomical data. While it is still a work in progress, we encourage all DASCH data users to give it a try and report their feedback.
StarGlass
The new StarGlass website provides a user interface and a programmatic API allowing access to DASCH plate-level data products and queries. While StarGlass does not provide access to DASCH lightcurve data, it does provide plate photographs and full-plate FITS “mosaics”. 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. Visit the StarGlass site to see what it holds and read the StarGlass API docs to learn how to fetch data from StarGlass systematically.
In the future, the DASCH team intends to add StarGlass support to the astroquery package, as well as to expose data through VO protocols as appropriate.
“Cannon” Data Portal
Alongside daschlab and StarGlass, you can also access DASCH data through the classic “Cannon” data portal. This website will be maintained indefinitely even as future development focuses on the more modern systems. The Cannon portal provides three main search mechanisms:
These let you do the following:
- Search Plates
- Locate plates by identifier or by sky location (using coordinates or object names); download plate imagery and metadata.
- Search Lightcurves
- Find and view lightcurves using coordinates or object names; download data tables, postage stamps.
- Browse Logbooks
- Browse and download photographs of the observing logs associated with the plates.
Note: temporary data access restrictions are in place on the Cannon data portal to prevent crawlers from overloading it. To avoid these, use daschlab or StarGlass, or see below for how to request access.
If you’re interested in a specific plate, you can pull up its information directly:
Temporary Data Access Restrictions
The DASCH “Cannon” data access portal currently does not allow downloads of whole-plate FITS images to prevent webcrawlers from overloading the server. Tabular lightcurve data, image cutouts, photos, and plate metadata are all available.
Separately, the most recent formal data release, DR6, was restricted to data at galactic latitudes b > 0. At the moment, retrieval of sky-based data is still subject to this restriction.
The daschlab toolkit and StarGlass do not impose these restrictions. If you are able to use them, please do so.
Our goal is to make all products available for direct download through the Cannon portal as well. As of March 2024, StarGlass is in beta-testing. Once it is shaken down, we will migrate Cannon to source its data from there, allowing us to remove the file download restrictions. We intend to remove the DR6 spatial restriction in conjunction with other major updates such as the StarGlass changeover.
In all cases, data are available upon request to the technical contact. This isn’t one of those “please go away” situations — we really do want people to get their hands on the files! It’s just that the Cannon site isn’t sophisticated enough to handle wide-open web traffic.
Members of the DASCH team have access to the private version of the Cannon portal.