We present a full sky 100 \micron map that is a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps , with the zodiacal foreground and confirmed point sources removed .
Before using the ISSA maps , we remove the remaining artifacts from the IRAS scan pattern .
Using the DIRBE 100 \micron and 240 \micron data , we have constructed a map of the dust temperature , so that the 100 \micron map may be converted to a map proportional to dust column density .
The dust temperature varies from 17 { ~ { } K } to 21 { ~ { } K } , which is modest but does modify the estimate of the dust column by a factor of 5 .
The result of these manipulations is a map with DIRBE-quality calibration and IRAS resolution .
A wealth of filamentary detail is apparent on many different scales at all Galactic latitudes .
In high latitude regions , the dust map correlates well with maps of H I emission , but deviations are coherent in the sky and are especially conspicuous in regions of saturation of H I emission toward denser clouds and the formation of { H } _ { 2 } in molecular clouds .
In contrast , high-velocity H I clouds are deficient in dust emission , as expected .

To generate the full sky dust maps , we must first remove zodiacal light contamination as well as a possible cosmic infrared background ( CIB ) .
This is done via a regression analysis of the 100 \micron DIRBE map against the Leiden-Dwingeloo map of H I emission , with corrections for the zodiacal light via a suitable expansion of the DIRBE 25 \micron flux .
This procedure removes virtually all traces of the zodiacal foreground .
For the 100 \micron map no significant CIB is detected .
At longer wavelengths , where the zodiacal contamination is weaker , we detect the CIB at surprisingly high flux levels of 32 \pm 13 { ~ { } nW / m } ^ { 2 } / { sr } at 140 \micron , and 17 \pm 4 { ~ { } nW / m } ^ { 2 } / { sr } at 240 \micron ( 95 \% confidence ) .
This integrated flux is \sim 2 times that extrapolated from optical galaxies in the Hubble Deep Field .

The primary use of these maps is likely to be as a new estimator of Galactic extinction .
To calibrate our maps , we assume a standard reddening law , and use the colors of elliptical galaxies to measure the reddening per unit flux density of 100 \micron emission .
We find consistent calibration using the ( { B } { - } { R } ) color distribution of a sample of 106 brightest cluster ellipticals , as well as a sample of 384 ellipticals with ( { B } { - } { V } ) and Mg line-strength measurements .
For the latter sample , we use the correlation of intrinsic ( { B } { - } { V } ) versus { Mg } _ { 2 } index to greatly tighten the power of the test .
We demonstrate that the new maps are twice as accurate as the older Burstein-Heiles reddening estimates in regions of low and moderate reddening .
The maps are expected to be significantly more accurate in regions of high reddening .
These dust maps will also be useful for estimating millimeter emission that contaminates CMBR experiments and for estimating soft X-ray absorption .

We describe how to readily access our maps for general use .