Preview Access to DASCH DR7 Now Available
2024 November 1
Here’s a slightly edited version of an email I sent to the DASCH Astrophysics mailing list at the end of the day yesterday:
I'm pleased to report that you can now get early, preview access to the DASCH Data Release 7 (DR7) data via the daschlab Python package.
DR7 will contain images of 428,408 photographic plates from the Harvard collection. Out of those, 414,748 have astrometric solutions; 361,689 have photometric calibrations based on the APASS reference catalog; and 379,754 have photometric calibrations from the ATLAS-refcat2 reference catalog. The ATLAS photometry collection consists of 27,966,413,880 measurements, while APASS has 23,574,404,199. Every part of the sky is covered by thousands of plates spanning about a century of observations.
This preview access comes with some important limitations to be aware of:
- Only the APASS photometric calibration is currently available; ATLAS will come later.
- The in-progress documentation hasn't been updated to reflect changes made during recent work to prepare for DR7. Nothing should be majorly off, but you might notice some inconsistencies or incompleteness. There are some nice data improvements that haven't yet been documented!
- While the preview access includes all major data products available in previous DASCH data releases (cutouts, lightcurves), it is still missing some elements that are likely to be of interest. Full-plate FITS images ("mosaics") can be downloaded via Starglass, but they still contain DR6 astrometry and some wonky headers. Valuable photometric calibration metadata are not yet available for retrieval.
- The DR7 data are being served by new AWS-based API endpoints that probably still have some lingering bugs.
- The classic "Cannon" DASCH data access portal, accessed via the
dasch.rc.fas.harvard.eduwebsite, is still serving DR6 data. - Due to extremely limited resources, daschlab (using Python and Jupyter) is going to be the only supported mechanism for DR7 preview access. If you want to work with DASCH data in another framework, however, the underlying data access APIs are all quite simple JSON exchanges.
To start exploring the DR7 early preview data:
- Make sure to install the very latest version of daschlab.
- Check out the updated "DRnext" documentation, especially the tutorials.
- Please send me your feedback! This is the most valuable thing you can do at this stage.