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

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