...Mpc.
For redshift z<<1 one can compute the distance of a galaxy or cluster of galaxies as 3#3, where c is the speed of light and 4#4 is the Hubble constant. Here a value of 5#5 Mpc/(km/s) has been used (1 parsec = 3.26 light years = 6#6 cm).

...system
Note that two factors fix the scale of a telescope+CCD detector system. One is the scale of the telescope, or how many millimeters on the focal plane correspond to one arcsec on the sky. The other is the pixel size of the CCD. Typical pixel sizes range from 10 to 30 110#110m.

Roberto Saglia
Thu Jul 31 19:08:37 MET DST 1997