3727$ doublet which places 7C1753+6311 at $z = 1.576$. This redshift is confirmed with corresponding H$\alpha$ emission by Rettura et al. (in preparation). []{data-label="fig:spectrum"}](spectrum.pdf){width="\columnwidth"}

We obtained a deep optical spectrum of C using the Low Resolution Imaging Spectrometer (LRIS; Oke et al. 1995) at the Keck I telescope during twilight on UT 2011 February 28. LRIS is a double spectrograph, and we integrated for 1200s on the blue arm and 1120s on the red arm in order to match read-out times. The observations used the 1.5 wide longslit and the data were processed using standard procedures and flux calibrated using an archival sensitivity function from 2011 April. Nothing is detected on the blue side, but a single, strong, high equivalent width emission line is detected at 9602Å on the red side, which we identify with the \[\] $\lambda 3727$ doublet at $z = 1.576$ (see Figure\[fig:spectrum\]). For the instrument configuration we used, the spectral resolving power was $R \equiv \lambda / \Delta \lambda = 1600$ for objects filling the slit at $\sim 9600$Å, which is insufficient to resolve the \[\] doublet. However, the redshift is confirmed by the detection of corresponding H$\alpha$ emission in a Keck near-infrared spectrum reported by 