All Figures

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{8267fg1.eps} \end{figure}$ Figure 1: Distribution of nights for the three observing sites. The time baseline is 78 days.
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In the text

$\begin{figure} \par\includegraphics[width=15.5cm,clip]{8267fg2.eps} \end{figure}$ Figure 2: The colour-magnitude diagram for M 4, showing the bump stars and part of the horizontal branch. The colours and magnitudes have been calibrated using the database provided by Stetson (2007). To show the range covered, some of the stars selected for a detailed analysis are indicated and labeled with the ID - see Table 2.
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In the text

$\begin{figure} \par\includegraphics[width=14.7cm,clip]{8267fg3.eps} \end{figure}$ Figure 3: The field of M 4 observed with the Danish 1.54 m telescope at La Silla. The 24 K giants we analysed in detail are marked by squares. The center of the field is at $\alpha_{2000} = 16^{\rm h}23^{\rm m}33\hbox{$.\!\!^{\rm s}$ }7$ , $\delta_{2000} = -26^{\circ}31'05\hbox{$.\!\!^{\prime\prime}$ }7$ .
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In the text

$\begin{figure} \par\includegraphics[width=6.8cm,clip]{8267fg4.eps} \end{figure}$ Figure 4: The rms scatter around the mean for a good night with the Danish 1.54 m telescope, for the ISIS1 reduction. The red open squares give the noise level for the final time series for the selected K giants in which we have looked for solar-like oscillations. The line indicates the noise expected from scintillation and photon statistics. The stars with high scatter near V=13.3 $\pm$ 0.3 are RR Lyrae stars. Saturation sets in at $V \sim 12.5$ .
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In the text

$\begin{figure} \par\includegraphics[width=6.8cm,clip]{8267fg5.eps} \end{figure}$ Figure 5: Same as Fig. 4, but for a bad night that was characterized by very a large sky background due to moon light.
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In the text

$\begin{figure} \par\includegraphics[width=6.8cm,clip]{8267fg6.eps} \end{figure}$ Figure 6: The mean rms scatter per data point per night, plotted against the nightly mean flux level in the exposures represented by a corresponding magnitude difference between each night and a reference night. The filled symbols indicate two nights with very few observations. The over-plotted diamonds indicate nights with a high sky level and the triangles show nights with very good seeing. The rms uncertainty is marked for each point.
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In the text

$\begin{figure} \par\includegraphics[width=6.7cm,clip]{8267fg7.eps}\hspace*{5mm} \includegraphics[width=6.7cm,clip]{8267fg8.eps} \end{figure}$ Figure 7: The mean scatter per data point per night for night 14 for the DAOPHOT ( left panel) and ISIS1 reduction ( right panel). The line gives the noise level for a good night (see Fig. 4).
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In the text

$\begin{figure} \par\includegraphics[width=6.9cm,clip]{8267fg9.eps}\hspace*{4mm} \includegraphics[width=6.9cm,clip]{8267fg10.eps} \end{figure}$ Figure 8: The rms noise level in K giant stars for La Silla data from two different nights. The noise level from the three reduction methods is similar for most stars, but in a few cases the DAOPHOT and ISIS2 noise levels are higher than for ISIS1.
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In the text

$\begin{figure} \par\includegraphics[width=6.9cm,clip]{8267fg11.eps} \end{figure}$ Figure 9: The rms noise levels in data from a good night at SSO. DAOPHOT is doing significantly worse than ISIS2. Notice the increased noise at faint magnitudes relative to the photon noise estimate (solid curve).
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In the text

$\begin{figure} \par\includegraphics[width=13.1cm,clip]{8267fg12.eps} \end{figure}$ Figure 10: Power spectra for the 12 K giants with the lowest noise at high frequencies. The luminosities of the stars increase from left to right and bottom to top. The predicted location of the maximum p-mode power and the acoustic cutoff frequency (indicated by thick black lines) shift to lower frequencies with increasing luminosity. Frequencies at multiples of 11.57 $\mu$ Hz (1 c/d) are indicated with vertical dashed lines.
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In the text

$\begin{figure} \par\includegraphics[width=6.25cm,clip]{8267fg13.eps} \end{figure}$ Figure 11: The autocorrelation of the spectral window for star #181. The vertical lines indicate peaks at 11.57, 5.84 and 0.81 $\mu$ Hz (1, 0.5 and 0.07 c/d). Note that multiples of the 0.81 $\mu$ Hz peak are present.
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In the text

$\begin{figure} \par\includegraphics[width=7.7cm,clip]{8267fg14.eps} \end{figure}$ Figure 12: Amplitude spectra for star #66, which is the brightest, non-saturated star in the subsample chosen for detailed analysis. Panel a) is the raw spectrum with one low frequency peak and a peak close to 2 c/d (23.14 $\mu$ Hz) marked. Panel b) shows the amplitude spectrum after subtracting the two peaks marked with vertical lines in panel a). Panel c) shows the spectral window, which is seen to contain a complex substructure around each 1 c/d sidelobe.
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In the text

$\begin{figure} \par\includegraphics[width=6.25cm,clip]{8267fg15.eps} \end{figure}$ Figure 13: The autocorrelation of the raw power spectrum for the giant star #181. Vertical lines represent peaks in the window function. The peak at 2.75 $\mu$ Hz could be the large separation, but might also be due to low frequency noise interacting with the window function.
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In the text

$\begin{figure} \par\includegraphics[width=5.35cm,clip]{8267fg16.eps}\vspace*{5mm} \includegraphics[width=5.35cm,clip]{8267fg17.eps} \end{figure}$ Figure 14: Autocorrelation of a simulation of star #292 including oscillations. In the top panel the spectrum of #292 was cleaned for multiples of 1 c/d before adding the simulated signal and in the bottom panel, the same procedure was followed as for the observed time series data. The red dotted lines correspond to multiples of the large separation in the simulated signal. The blue vertical lines indicate parasitic peaks from the window function at 0.85 and 11.57 $\mu$ Hz (see Fig. 12).
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In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{8267fg18.eps} \end{figure}$ Figure 15: Average smoothed spectra for three groups of observed K giants with luminosity $L \simeq 60$ , 80 and $130~{L}_{\odot}$ . The faint group (raw and clean version) are the blue lines, the average group is plotted as the magenta line and the bright group is the red line. The bottom curve is the faint group after multiples of 1 c/d are removed. The black solid line is for a simulation of star #292 with peak oscillation amplitudes of A = 400 ppm.
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In the text

$\begin{figure} \par\includegraphics[width=7.25cm,clip]{8267fg19.eps} \end{figure}$ Figure 16: Power density for three cases: 1) the observed star #66 (red, solid line), 2) a scaled power spectrum including granulation, p-modes with A = 300 ppm and white noise as star #66 (blue, dashed line), 3) the simulation by Svensson and Ludwig (2005) (black, dotted line).
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{8267fg1.eps} \end{figure}$	Figure 1: Distribution of nights for the three observing sites. The time baseline is 78 days.
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$\begin{figure} \par\includegraphics[width=15.5cm,clip]{8267fg2.eps} \end{figure}$	Figure 2: The colour-magnitude diagram for M 4, showing the bump stars and part of the horizontal branch. The colours and magnitudes have been calibrated using the database provided by Stetson (2007). To show the range covered, some of the stars selected for a detailed analysis are indicated and labeled with the ID - see Table 2.
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$\begin{figure} \par\includegraphics[width=14.7cm,clip]{8267fg3.eps} \end{figure}$	Figure 3: The field of M 4 observed with the Danish 1.54 m telescope at La Silla. The 24 K giants we analysed in detail are marked by squares. The center of the field is at $\alpha_{2000} = 16^{\rm h}23^{\rm m}33\hbox{$.\!\!^{\rm s}$ }7$ , $\delta_{2000} = -26^{\circ}31'05\hbox{$.\!\!^{\prime\prime}$ }7$ .
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$\begin{figure} \par\includegraphics[width=6.8cm,clip]{8267fg5.eps} \end{figure}$	Figure 5: Same as Fig. 4, but for a bad night that was characterized by very a large sky background due to moon light.
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$\begin{figure} \par\includegraphics[width=6.7cm,clip]{8267fg7.eps}\hspace*{5mm} \includegraphics[width=6.7cm,clip]{8267fg8.eps} \end{figure}$	Figure 7: The mean scatter per data point per night for night 14 for the DAOPHOT ( left panel) and ISIS1 reduction ( right panel). The line gives the noise level for a good night (see Fig. 4).
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$\begin{figure} \par\includegraphics[width=6.9cm,clip]{8267fg9.eps}\hspace*{4mm} \includegraphics[width=6.9cm,clip]{8267fg10.eps} \end{figure}$	Figure 8: The rms noise level in K giant stars for La Silla data from two different nights. The noise level from the three reduction methods is similar for most stars, but in a few cases the DAOPHOT and ISIS2 noise levels are higher than for ISIS1.
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$\begin{figure} \par\includegraphics[width=6.9cm,clip]{8267fg11.eps} \end{figure}$	Figure 9: The rms noise levels in data from a good night at SSO. DAOPHOT is doing significantly worse than ISIS2. Notice the increased noise at faint magnitudes relative to the photon noise estimate (solid curve).
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$\begin{figure} \par\includegraphics[width=6.25cm,clip]{8267fg13.eps} \end{figure}$	Figure 11: The autocorrelation of the spectral window for star #181. The vertical lines indicate peaks at 11.57, 5.84 and 0.81 $\mu$ Hz (1, 0.5 and 0.07 c/d). Note that multiples of the 0.81 $\mu$ Hz peak are present.
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$\begin{figure} \par\includegraphics[width=6.25cm,clip]{8267fg15.eps} \end{figure}$	Figure 13: The autocorrelation of the raw power spectrum for the giant star #181. Vertical lines represent peaks in the window function. The peak at 2.75 $\mu$ Hz could be the large separation, but might also be due to low frequency noise interacting with the window function.
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$\begin{figure} \par\includegraphics[width=7.25cm,clip]{8267fg19.eps} \end{figure}$	Figure 16: Power density for three cases: 1) the observed star #66 (red, solid line), 2) a scaled power spectrum including granulation, p-modes with A = 300 ppm and white noise as star #66 (blue, dashed line), 3) the simulation by Svensson and Ludwig (2005) (black, dotted line).
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