UIST Imaging
|
Imaging: Saturation and Sky Counts
|
|
Note that saturation magnitudes (the brightest point source that can be observed at the
shortest possible exposure time for each mode) are very seeing dependent.
| Plate |
Filter |
Sky |
Background |
Saturation Mag |
| Scale |
  |
Counts |
Brightness |
Limited |
0.5" seeing |
| "/pix |
  |
/sec/pix |
mag/sq." |
Exp Time, sec |
1024x1024 |
512x512 |
| 0.12 |
J |
2.4 |
15.7 |
30 |
7.3 |
6.0 |
|   |
H |
17 |
13.9 |
12 |
8.3 |
7.0 |
|   |
K |
12 |
13.5 |
15 |
6.9 |
5.6 |
|   |
L' |
26,000 |
4.0 |
0.03 |
4.5 |
3.5 |
|   |
M' |
57,000 |
1.0 |
0.01 |
N/A |
1.7 |
|   |
Klong |
13 |
- |
15 |
- |
- |
|   |
nb-K |
0.8 |
13.5 |
55 |
3.9 |
2.6 |
|   |
3.0-3.3um nb |
500 |
- |
0.4 |
- |
- |
|   |
4.0um nb |
1580 |
- |
0.1 |
- |
- |
| 0.06 |
J |
0.62 |
15.7 |
60 |
5.8 |
4.5 |
|   |
H |
4.4 |
13.9 |
20 |
6.8 |
5.5 |
|   |
K |
3.1 |
13.5 |
25 |
5.4 |
4.1 |
|   |
L' |
6,000 |
4.0 |
0.17 |
2.9 |
1.9 |
|   |
M' |
14,000 |
1.0 |
0.07 |
1.0 |
0.0 |
|   |
nb-K |
0.18 |
13.5 |
80 |
2.4 |
1.1 |
|   |
nb-L'-M |
25-700 |
- |
10-1 |
- |
- |
A saturated frame has a typical pattern as shown below.
An exposure consists of a single global reset followed by two or more
reads of array where the four quadrants are read out in parallel, from
the outer corner towards the center. The output image is the difference
between the reads so that the interval between reads is constant across
the array. The center of the array is always exposed longer in
this read mode and hence in the case of a high background the center
will saturate sooner than the outer regions; a
saturated NDSTARE frame has a characteristic pattern with a strong
gradient in counts across the frame, as shown in the image below.
|