DASCH Data Release 1 (DR1)
and Data Release for Development Fields

The Digital Access to a Sky Century @ Harvard (DASCH) project is pleased to release its first production data release (DR1), covering Galactic latitude b = +90 - +75deg, as well as results from the 5 Development Fields from which the hardware and software pipelines for DASCH were developed. These represent <10% of the Harvard plate data (1885 - 1992; full-sky). A brief overview of DASCH is given in Grindlay et al (2012) Opening the 100-Year Window for Time Domain Astronomy in arXiv:1211.1051 or IAU Symposium Vol. 285 p 29-34 . Additional project papers are listed in the DASCH publications web page. Digitized images (11 micron pixels) of~45,000 plates and their fully reduced WCS solutions and SExtractor-based photometry of every resolved object are available from this Data Release from the ~90Tb of data on disk now available. Light curves (LCs) typically include ~1500 points for an object with magnitude B ~12-13. LCs may be retrieved from input coordinates or SIMBAD object names for up to 10 at a time, and LC plots, data and images for each then downloaded individually.

Provided subsequent support is obtained, 4 additional 15deg increments in galactic latitude (b = 75 - 15deg) will be released as DR2 - DR5, followed by DR6 - DR10 for the southern galactic cap (b = -90 - -15deg) and then DR11 - DR12 (b = -15 - +15) for the Galactic Plane, all by 2016.

Production scanning of the Harvard Plates is proceeding with plate centers in the 10 x 10 deg bins in Galactic Coordinates (l, b) and sequence of bins shown in the plot on the left.

Release Fields

Region	Galactic Longitude (l) degrees	Galactic Latitude (b) degrees	RA hours	RA degrees	Dec degrees	Radius degrees
DR1	0 to 360	75.00 to 90.00	12h51m	192.86	27.13	15

The Development Fields are listed in the Table below and are centered on the coordinates given. Since adjacent fields have not yet been scanned, they are increasingly incomplete with increasing radius. These fields will be integrated into the Production scanning as they are covered in the data release plan described above.

Development Fields

Region	Galactic Longitude (l) degrees	Galactic Latitude (b) degrees	RA hours	RA degrees	Dec degrees	Radius degrees
M44	205.91	32.48	8h40m	130.09	19.67	5
3C273	289.96	64.36	12h29m	187.27	2.05	5
Baade's Window	1.03	-3.91	18h03m	270.88	-30.02	5
Kepler Field	76.34	13.45	19h22m	290.73	44.50	8
LMC	280.47	-32.89	5h23m	80.89	-69.76	5

Release Fields Coverage Plots vs. Limiting Magnitude

All limiting magnitude coverage plots below have a resolution of one degree. The red angular borders around the coverage area are artifacts of the plot shading algorithm. The plots below that the GSC2.3.2 calibration catalog has the largest range of magnitude coverage (7-18) while the APASS DR6 calibration catalog and the Kepler Input Catalogs have ranges of approximately 9 to 17. The APASS DR6 catalog provides the most accurate photometry calibration, but is not yet complete in all regions of the sky. The wide field patrol plates which make up most of the collection have a limiting magnitude of approximately 12 before circa 1935 and 14 after that date. For each field, the GSC2.3.2 calibration catalog results appear on top for limiting magnitudes 8, 10, 12, 14, and 16; and the APASS DR6 catalog results appear on bottom for limiting magnitudes 9, 10, 12, 14, and 16.

DR1: b = 90deg to 75deg

This field is centered on the North Galactic Pole and has a radius of 15 degrees. The APASS DR6 calibration catalog is not complete in this region.

M44 Cluster Field

This field is the first scanned because of the availability of accurate photometric catalogs.

3C273 Quasar Field

This field is the second scanned to investigate the usefulness of DASCH photometry for the study of quasars.

Baade's Window Field

This field is the third scanned to study algorithms for nova searches and to test DASCH astrometry and photometry in crowded fields. The APASS DR6 catalog is not complete in this region.

Kepler Field

This field is the fourth scanned to take advantage of the superior accuracy of the Kepler Input Catalog over the GSC2.3.2 catalog for the calibration of DASCH plates. Kepler Input Catalog calibrations are available for this field only and are shown in the middle set of graphs for limiting magnitudes 9, 10, 12, 14, and 16.

Large Magellanic Cloud Field

Because of the historic discoveries made by Henrietta Leavitt, the LMC field provides the deepest magnitude coverage and highest plate density for the Harvard plates scanned to date. Improved photometry (for crowded fields) will be done for both the LMC and Baade's Window when these fields are re-processed for Production scanning.

Acknowledgements

The DASCH project at Harvard is grateful for partial support from NSF grants AST0407380 and AST0909073, which should be acknowledged in all papers making use of DASCH data.

We acknowledge the one-time gift of the Cornel and Cynthia K. Sarosdy Fund for DASCH, and thank Grzegorz Pojmanski of the ASAS project for providing some of the source code on which the DASCH web-interface is based.

The ongoing AAVSO Photometric All-Sky Survey (APASS) has improved DASCH photometric calibration and is funded by the Robert Martin Ayers Sciences Fund.