J (1.2 m) and K (2.2
m) photometry of King 5
was obtained
at the 1.5 m Gornergrat Infrared Telescope (TIRGO)
equipped with Arcetri Near Infrared Camera (ARNICA)
in October 1997.
ARNICA is based on a NICMOS3 256
256
pixels array (gain = 20 e-/ADU, read-out noise = 50 e-,
angular scale = 1
pixel, and
field of
view).
More details about the observational equipment and infrared camera,
and the reduction procedure can be found in Carraro et al. (1999a).
Through each filter 4 partially overlapping images of
each field were obtained,
covering a total field of view of about 8
8
,
in short exposures to avoid sky saturation.
One field is located close to the center of King 5.
In addition, a sample of the background population of King 5 was
obtained observing a field of
at about
South-East from the cluster center
and a second one of the same dimensions located at about
Northward.
The log-book of the observations is presented
in Table 1 where the centers of the observed fields and the total
exposure times are given.
The nights were photometric
with a seeing of
.
Figure 1 presents the final mosaic of the 4 frames
for King 5 in K passband.
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Figure 3:
The CMD of two comparison fields taken
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The conversion of the instrumental magnitude j and k to the standard J, K was made using stellar fields of standard stars taken from Hunt et al. (1998) list. About 10 standard stars per night have been used. In addition 2 stars (thereafter K5A and K5B) inside the field have been measured with a photometer and used for the calibration. Results are summarized in Table 2.
The relations in usage per 1 s exposure time are:
J = j+19.51 | (1) |
K = k+18.94 | (2) |
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