Sabater, J.J.SabaterBest, P. N.P. N.BestTasse, C.C.TasseHardcastle, M. J.M. J.HardcastleShimwell, T. W.T. W.ShimwellNisbet, D.D.NisbetJelic, V.V.JelicCallingham, J. R.J. R.CallinghamRöttgering, H. J. A.H. J. A.RöttgeringBONATO, MATTEOMATTEOBONATOBONDI, MARCOMARCOBONDICiardi, B.B.CiardiCochrane, R. K.R. K.CochraneJarvis, M. J.M. J.JarvisKondapally, R.R.KondapallyKoopmans, L. V. E.L. V. E.KoopmansO'Sullivan, S. P.S. P.O'SullivanPRANDONI, ISABELLAISABELLAPRANDONISchwarz, D. J.D. J.SchwarzSmith, D. J. B.D. J. B.SmithWang, L.L.WangWilliams, W. L.W. L.WilliamsZaroubi, S.S.Zaroubi2025-02-192025-02-1920210004-6361http://hdl.handle.net/20.500.12386/36076The LOFAR Two-metre Sky Survey (LoTSS) will cover the full northern sky and, additionally, aims to observe the LoTSS deep fields to a noise level of ≲10 μJy beam<SUP>−1</SUP> over several tens of square degrees in areas that have the most extensive ancillary data. This paper presents the ELAIS-N1 deep field, the deepest of the LoTSS deep fields to date. With an effective observing time of 163.7 h, it reaches a root mean square noise level of ≲20 μJy beam<SUP>−1</SUP> in the central region (and below 30 μJy beam<SUP>−1</SUP> over 10 square degrees). The resolution is ~6 arcsecs and 84 862 radio sources were detected in the full area (68 square degrees) with 74 127 sources in the highest quality area at less than 3 degrees from the pointing centre. The observation reaches a sky density of more than 5000 sources per square degree in the central region (~5 square degrees). We present the calibration procedure, which addresses the special configuration of some observations and the extended bandwidth covered (115-177 MHz; central frequency 146.2 MHz) compared to standard LoTSS. We also describe the methods used to calibrate the flux density scale using cross-matching with sources detected by other radio surveys in the literature. We find the flux density uncertainty related to the flux density scale to be ~6.5 per cent. By studying the variations of the flux density measurements between different epochs, we show that relative flux density calibration is reliable out to about a 3 degree radius, but that additional flux density uncertainty is present for all sources at about the 3 per cent level; this is likely to be associated with residual calibration errors, and is shown to be more significant in datasets with poorer ionosphere conditions. We also provide intra-band spectral indices, which can be useful to detect sources with unusual spectral properties. The final uncertainty in the flux densities is estimated to be ~10 per cent for ELAIS-N1. <P />Catalogs and images are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/648/A2">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/648/A2</A> <P />The data associated with this article are released at: <A href="https://lofar-surveys.org">https://lofar-surveys.org</A>STAMPAen10.1051/0004-6361/202038828https://www.aanda.org/articles/aa/full_html/2021/04/aa38828-20/aa38828-20.html2021A&A...648A...2SFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation