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PRO-AM collaborations in Planetary Astronomy

5

can produce non-desired forces acting on the mechanics (e.g. wind, resonances of
proper frequencies). The mechanics must damp efficiently these effects. Another
constraint concerns the most frequently encountered classical German equatorial
mounts. They are very compact, but the so-called “meridian flip” induces a rotation
of 180◦ of the observed field of view. The use of calibration frames (e.g. flat fields)
must take into account the tube orientation choice. Many mounts are equipped with a
GOTO system that is generally presented as a pad or a computer linked to the mount
sending the celestial coordinates of the object to point. It is important to verify that
the accuracy of the GOTO system is compatible with the precision to reach.
Recent progresses in electronics, mechanics and computer science allow the
building of robotic observatories [39]. These remote controlled observatories can
provide very high duty cycles by optimizing the time on the sky. When they are
autonomous (i.e. no human presence) the requirements on hardware and software
are significant. It must be noticed that a robotic observatory setup is generally fixed
to keep the same calibrations from night to night.

2.2 Detectors
Many manufacturers propose very different cameras for astronomy. The characteristics described in this section are important to fit the science goals. Sections 2.2.1
and 2.2.2 describe the camera types that can be used by amateur astronomer. Section 2.2.3 is devoted to the specificity of high resolution often demanded in planetary
science.
Digital cameras are based on a matrix of pixels that converts photons into electrons. The quantum efficiency of the conversion, the maximum of electrons by pixel,
the size and the number of pixels are the main factors of such a matrix. The electronics associated to the chip detector play also an important role with respect to
the scientific constraints. The gain gives the conversion from electrons to analog to
digital units (ADU) and is expressed in electron/ADU. A high value is usually used
for bright objects (planetary surfaces) and low values for deep sky. Some cameras
allow changing the gain by software, thus giving a high versatility for various topics.
The readout noise adds a stochastic component to the signal [99]. Low readout of
noise is always preferable, but the value increases as the readout speed diminishes.
The thermal noise is very low in recent cameras, but for exposures longer than a few
seconds it remains necessary to cool the chip. However, thermoelectric cooling (by
Pelletier modules) and air dissipation is enough for all cameras usable for amateur
of astronomy.
To obtain accurate photometry of the planets Uranus and Neptune, it can be useful to use a mono pixel detector as a photometer. The science described in Sec. 6.6.1
and 6.6.2 is obtained with an OPTEC SSP-3 photometer equipped with a S1087-01
photodiode manufactured by Hamamatsu. There is only one readout that generates
much less noise than a matrix of pixels. In this case there is no spatial information