The DASCH project has been a herculean effort spanning two decades. In order to ensure that the plate scanning is brought to completion, and that the resulting data are archived and as useful as possible, the project is undergoing an overhaul under the direction of the Harvard College Observatory. During this time, our servers will be down and access to DASCH data via existing interfaces will be limited. Please contact Purvang Patel, Executive Director at the Harvard College Observatory, if you have questions.

Enter the J2000 object position or a Simbad-searchable reference in the box below and press Search to obtain the lightcurve query results in a separate window. The search center is currently restricted to released regions, a maximum of ten entries, and a maximum search radius is 60 arcsec. Note that the positions returned by Simbad may not necessarily match the DASCH positions because of discrepancies between catalogs. DASCH positions are corrected by UCAC4 proper motions until May 31, 2018 when we switched to UCAC5 proper motions. The latter positions may be identified by a versionId of 173 or later.

N >= d <= arcsec
Source: APASS Input Catalog (B-band) Kepler Input Catalog (g-band) GSC2.3.2 Catalog (JpgMag) ATLAS refcat2 (gmag) NOTE: New default choice.
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We are currently using the ATLAS All-Sky Stellar Reference Catalog, the AAVSO Photometry All-Sky Survey (APASS) Release 8 Catalog , the Kepler Input Catalog (KIC), and the GSC2.3.2 Hubble Guide Star Catalog for photometry calibration. The ATLAS refcat2 calibration uses Pan-STARRS DR1 supplemented with reflattened APASS, SkyMapper DR1, APASS DR9, Tycho-2, and the Yale Bright Star Catalog to give the best photometric accuracy to 19th magnitude over the entire sky. The APASS calibration uses Johnson B and V magnitudes which better match the unfiltered photographic blue of most of the plates. The KIC calibration gives better accuracy than the Guide Star Catalog for the field of the Kepler satellite. The GSC2.3.2 catalog provides B and V magnitudes for objects outside the 9 to 15 magnitude range of APASS. An overview of DASCH calibration appears in Laycock, S. et. al, Digital Access to a Sky Century at Harvard. II: Initial Photometry and Astrometry and in Sumin Tang et al., Improved Photometry for the DASCH pipeline . An overview of the DASCH pipeline appears in the project photometry page.


Objects in the Kepler field calibrated with the Kepler Catalog (KIC) have g-band magnitudes; objects calibrated with APASS have B-band magnitudes; objects calibrated with GSC2.3.2 have JpgMag (IIIaJ) magnitudes; and objects calibrated with ATLAS refcat2 have g-band magnitudes. Objects, particularly red stars, calibrated with Sloan g and r magnitudes may introduce systematic errors.

To access photometric data enter object ID's (one per line) in the window above. Valid identifications are: J2000 RA DEC (5.45 -81.5 or 5:26:50 -81:35:12 or 8 41 43.8 +19 43 33.5 where a +declination sign is mandatory in the third case only), GSC2.3.2 ID (for the gsc2.3.2 dataset only; e.g. N2312220195 or N120013341), Kepler Input Catalog ID (for the KIC dataset only; e.g. K3433237), APASS Catalog ID (for the APASS dataset only; e.g. APASS_J115140.7+020334), Simbad-searchable object name (XX Dor), or DASCH object (DASCH_J123349.2-113822), i.e. an object which does not have a matching catalog entry. For ATLAS refcat2, see the description of the REF variable. All stars within d arcsecs from center, having more than N measurements will be listed. Because of astrometry issues inherent in the processing of old photographic plates, measurements of interest may appear in adjacent lightcurves. To obtain object's light curve, click on its listed ID in the query results window. Data tables for all points returned by the query may be obtained by selecting the Download all points in table form. link at the bottom of the query results window. WARNING: The Simbad name resolution service has been intermittently unreliable from this web site. If you experience problems, please retrieve the coordinates directly from the Simbad reflector site.

Acknowledgements

The DASCH project at Harvard is grateful for partial support from NSF grants AST-0407380, AST-0909073, and AST-1313370; 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.