Survey Wavelengths and Sky Coverage

DSS images have one-arsecond pixels and use three broad-band filters covering roughly 3950 Å to 9000 Å. SDSS has smaller pixels (0.39 arcsec) and uses narrower filters in five bands between 3551 Å and 8931 Å. 2MASS has 1 arcsecond pixels and used three near-infrared bands between 1.24 and 2.16 μm.

DSS and 2MASS are all-sky. SDSS DR7 covers 11663 square degrees, mostly in the north galactic polar region. For more information, see below.

DSS    The photographic plates scanned for the Digitized Sky Surve y were taken through relatively wide spectral filters. None of the underlying datasets are all-sky; the DSS "surveys" are actually composites of multiple image sets taken at different times using different instruments. For more detailed information on filters, dates, and coverage, see

http://gsss.stsci.edu/SkySurveys/SkySurveys.htm

Users should be aware that there is some overlap here. For instance, SE RC-J (which covers much of the southern hemisphere) is used in both the compo site surveys GSC1 and DSS2B.

Image Band Approximate
wavelength range
DSS1B Bj 3950 - 5400 Å
DSS1R R 6125 - 6475 Å
DSS2B Bj 3950 - 5400 Å
DSS2R R 6300 - 6900 Å
DSS2IR I 6950 - 9000 Å
 
SDSS    The Sloan Digital Sky Survey will map in detail one-quarters of the sky (concentrating on the north polar cap). Data Release 7 (DR7) covers 11663 square degrees .
Image Approximate wavelength
u 3551 Å
g 4686 Å
r 6165 Å
i 7481 Å
z 8931 Å
 
2MASS    The Two Micron All-Sky Survey covers the whole sky in three near-infrared bands.
Image Approximate wavelength
J 1.24 μm
H 1.66 μm
Ks 2.16 μm