Astronomy Principles and Practice Fourth Edition.pdf

Digital photography 449
Figure 24.32. Laboratory equipment for simulating Michelson’s stellar interferometer.
position relative to the image plane of the objective by measuring the position of the double slit when
it is viewed to be in focus in the microscope.
Using the travelling microscope, obtain a mean value for the separation of the slits. By assuming
the mean wavelength of the light to be 5500 Å and knowing the focal length of the objective, calculate
the angular size of the artificial star using the formula
α = 1·22λ
a ′ min
= 1·22λD min
.
aF
As a check, calculate the actual angle subtended by measuring the physical size of the hole
constituting the artificial star and the distance of the star from the objective.
24.12 Digital photography
The advent of two-dimensional solid state detectors has revolutionized ‘photography’. The use of
digital cameras for everyday use is now fairly common. Such equipment used for landscapes and
portraits automatically provides colour pictures. Some of the latest models (SLR) have detachable
lenses and could, in principle, be attached at the focus of a telescope without the camera lens being
attached. However, there is no facility to make long exposures and, without cooling, the recorded
pictures would be very subject to thermal noise. The formatting of the files is also generally not