Observations
The observing strategy for the HDF-S was similar to that of the HDF-N, with the same optical filters used for the WFPC2 images (isolating wavelengths at 300, 450, 606 and 814 nanometres), and similar total exposure times. The observations were made over 10 days in September and October 1998, a total of 150 orbits, and had a total exposure time of over 1.3 million seconds. While the WFPC2 took very deep optical images, the fields were simultaneously imaged by the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). A number of flanking fields were also observed for shorter periods of time.
The WFPC2 image is 5.3 square arcminutes, whilst the NICMOS and STIS images are only 0.7 square arcminutes.
| Camera | Filter | Wavelength | Total exposure time | Exposures |
|---|---|---|---|---|
| WFPC2 | F300W | 300 nm (U-band) | 140,400 s | 106 |
| WFPC2 | F450W | 450 nm (B-band) | 103,500 s | 67 |
| WFPC2 | F606W | 606 nm (V-band) | 99,300 s | 53 |
| WFPC2 | F814W | 814 nm (I-band) | 113,900 s | 57 |
| NICMOS NIC3 | F110W | 110 nm (J-band) | 162,600 s | 142 |
| NICMOS NIC3 | F160W | 160 nm (H-band) | 171,200 s | 150 |
| NICMOS NIC3 | F222M | 222 mm (K-band) | 105,000 s | 102 |
| STIS | 50CCD | 350–950 nm | 155,600 s | 67 |
| STIS | F28X50LP | 550–960 nm | 49,800 s | 64 |
| STIS | MIRFUV | 150–170 nm | 52,100 s | 25 |
| STIS | MIRNUV | 160–320 nm | 22,600 s | 12 |
| Spectroscopy | G430M | 302.2–356.6 nm | 57,100 s | 61 |
| Spectroscopy | G140L | 115–173 nm | 18,500 s | 8 |
| Spectroscopy | E230M | 227.8–312 nm | 151,100 s | 69 |
| Spectroscopy | G230L | 157–318 nm | 18,400 s | 12 |
As with the HDF-N, the images were processed using a technique known as 'drizzling', in which the telescope pointing was changed by a very small amount between exposures, and the resulting images combined using sophisticated techniques to achieve a higher angular resolution than would otherwise be possible. Translational changes were fine during the imaging parts of the observation; however, the telescope had to be rotated by small amounts instead of repointed during the spectroscopic work, such that the centre of the STIS instrument was kept on the central quasar. The HDF-S final image had a pixel scale of 0.0398 arcseconds.
Read more about this topic: Hubble Deep Field South
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