Survey Wavelengths, Resolutions and Sky Coverage

The Digital Sky Survey (DSS) is actually a collection of surveys covering various parts of the sky using ten different emulsion/filter combinations between 2950 and 9700 Angstrom. Some images have 1.0 arcsecond resolution and some 1.7 arcsecond resolution. 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.

Coverage 2MASS and some of the DSS combination surveys 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 Survey 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, SERC-J (which covers much of the southern hemisphere) is used in both the composite surveys GSC1 and DSS2B. GSC2 is actually the same data as DSS2R.

Image Band Approximate wavelength range
DSS1B Opg 2950 - 5400 Å
DSS1R Epg 5950 - 7050 Å
DSS2B Jpg 3400 - 6000 Å
DSS2R Fpg 5900 - 7150 Å
DSS2IR Ipg 7000 - 9700 Å
Quick-V Vpg 4900 - 6800 Å
GSC2 Fpg 5900 - 7150 Å
GSC1 Vpg (North)
Jpg (South)
Vpg (S. Gal plane)
and miscellaneous
4900 - 6800 Å
3450 - 6000 Å
4650 - 6800 Å
SDSS   The Sloan Digital Sky Survey will map in detail one-quarters of the sky (concentrating on the Galactic 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. The user has a choice between the nominal "single coverage" data and the "full survey" data which goes much deeper in a few regions. See

for more information.

Image Approximate wavelength
J 1.24 μm
H 1.66 μm
Ks 2.16 μm