  We want to study whether the astrometric and photometric accuracies obtained
for the Carte du Ciel plates digitized with a commercial digital camera are
high enough for scientific exploitation of the plates.
  We use a digital camera Canon EOS~5Ds, with a 100mm macrolens for digitizing.
We analyze six single-exposure plates and four triple-exposure plates from the
Helsinki zone of Carte du Ciel (+39 degr < delta < 47 degr). Each plate is
digitized using four images, with a significant central area being covered
twice for quality control purposes. The astrometric calibration of the
digitized images is done with the data from the Gaia TGAS (Tycho-Gaia
Astrometric Solution) of the first Gaia data release (Gaia DR1), Tycho-2, HSOY
(Hot Stuff for One Year), UCAC5 (USNO CCD Astrograph Catalog), and PMA
catalogs.
  The best astrometric accuracy is obtained with the UCAC5 reference stars. The
astrometric accuracy for single-exposure plates is sigma(R.A.)=0.16" and
sigma(Dec.)=0.15" expressed as a Gaussian deviation of the astrometric
residuals. For triple-exposure plates the astrometric accuracy is
sigma(R.A.)=0.12" and sigma(Dec.)=0.13". The 1-sigma uncertainty of photometric
calibration is about 0.28 mag and 0.24 mag for single- and triple-exposure
plates, respectively. We detect the photographic adjacency (Kostinsky) effect
in the triple-exposure plates.
  We show that accuracies at least of the level of scanning machines can be
achieved with a digital camera, without any corrections for possible
distortions caused by our instrumental setup. This method can be used to
rapidly and inexpensively digitize and calibrate old photographic plates
enabling their scientific exploitation.
