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The Extreme Ultraviolet Explorer's (EUVE's) deep-survey telescope image system views the sky through two wavelength band filters, 50--190~\AA\ and 160--360~\AA, spanning the short-wavelength portion of the EUV. A part of the spacecraft's commissioning, a deep first-light sky exposure in the direction of ($l$=5.6, $b$=+1.3) was taken. Analysis has permitted a precise assessment of the observing background for this image, from which we obtain two immediate results: (1) in the 50--190~\AA\ band we see an effective continuum flux of $1.71 \pm 0.17$ photons cm$^{-2}$ s$^{-1}$ sr$^{-1}$ \AA$^{-1}$, consistent with the Wisconsin B band survey in this direction and the ROSAT WFC S1 flux; (2) in the 160--360 band we establish a $3 \sigma$ upper flux limit of 3.63 photons cm$^{-2}$ s$^{-1}$ sr$^{-1}$ \AA$^{-1}$, far lower than previous efforts. Finally, we apply these fluxes to constrain isothermal plasma emission models for the local interstellar medium; we find that no simple isothermal model satisfactorily fits all the data, but that areas of closest agreement occur for log T of 5.85 and 6.20.
This work has been supported by NASA contract NAS5-30180.
