possible on a diurnal basis—Mkn 421 [@Daniel], Mkn 501 [@David], and PKS 2155-304 [@2155].

Intrinsic Energy Spectrum
-------------------------

Having to traverse a cosmological distance corresponding to a redshift of $z=0.044$, the $\gamma$-rays emitted by 1ES2344+514 interact with the low energy photons of the EBL (see, e.g., Nikishov 1962; Gould & Schréder 1966; Hauser & Dwek 2001). The predominant reaction $
\gamma_{\mbox{\scriptsize{\,VHE}}} + \gamma_{\mbox{\scriptsize
EBL}} \rightarrow \mathrm{e}^{+}\,\mathrm{e}^{-}$ leads to an attenuation of the intrinsic spectrum $\mathrm{d}N/\mathrm{d}E_\mathrm{intr}$ that can be described by $$\mathrm{d}N/\mathrm{d}E_\mathrm{obs} \,=\,
\mathrm{d}N/\mathrm{d}E_\mathrm{intr} \cdot
\exp[-\tau_{\gamma\gamma}(E,\,z)]$$ with the observed spectrum $\mathrm{d}N/\mathrm{d}E_\mathrm{obs}$, and the energy-dependent optical depth $\tau_{\gamma\gamma}(E,\,z)$. Here we use the “best-fit” model of @kneiske, which yields an EBL spectrum that agrees with alternative models, e.g. @stecker. Using this EBL spectrum and a state-of-the-art cosmology (flat universe, Hubble constant $H_0=72\,\mathrm{km}\,\mathrm{s}^{-1}\,
\mathrm{Mpc}^{-1}$, matter density $\Omega_\mathrm{m}=0.3$, and dark energy density $\Omega_{\Lambda}=0.7$), we calculate the optical depth $\tau_{\gamma\gamma}$ for the distance of 1ES2344+514. Thereby we use the numerical integration given by eq. 2 in @dwek. The reconstructed intrinsic source spectrum is shown along with the measured spectrum in Fig. \[fig:spectrumdeabs\]. The intrinsic source spectrum can be described by a simple power law of the form $$\frac{\mathrm{d}N}{\mathrm{d}E}_\mathrm{intr} = \frac{
(2.1\pm{1.2_\mathrm{stat}}\pm{0.5_\mathrm{syst}})\cdot10^{-11}}{
\mathrm{TeV}\,\mathrm{cm}^2\,\mathrm{s}} \times \frac{E}{500\,
\mathrm{GeV}}^{-2.66\pm{0.50_\mathrm{stat}}\pm{0.20_\mathrm{syst}}}$$ between 