Table 2
Comparison of discrepancies as a function of the PSF fitting radius.
| Figure | Radius at Max S/N | Radius at 1.2×FWHM | Radius at 10% Discrepancy | F | B | F/B |
|---|---|---|---|---|---|---|
| /Discrepancy | /Discrepancy | /Discrepancy | e− | e− | ||
| – | 0.8″/48% | 0.6″/44% | 1.5″/10% | 20 000 | 2025 | 9.87 |
| – | 0.4″/92% | 0.6″/78% | 2.1″/10% | 2000 | 1025 | 1.95 |
| – | 0.4″/91% | 0.6″/78% | 2.7″/10% | 100 | 1000 | 0.10 |
| – | 0.6″/39% | 0.6″/39% | 0.8″/10% | 100 000 | 1025 | 97.56 |
| (a) | 1.08″/45% | 1.2″/38% | 2.09″/10% | 100 000 | 1625 | 61.54 |
| (b) | 0.69″/85% | 1.2″/56% | 3.30″/10% | 2000 | 1625 | 1.23 |
| (c) | 0.70″/85% | 1.2″/46% | 2.80″/10% | 8000 | 825 | 9.69 |
| (d) | 1.08″/44% | 1.2″/37% | 1.84″/10% | 80 000 | 825 | 96.96 |
| – | 1.58″/56% | 1.8″/28% | 2.8″/10% | 100 000 | 1625 | 61.54 |
| – | 0.90″/85% | 1.8″/47% | 3.7″/10% | 2000 | 1625 | 1.23 |
| – | 1.10″/85% | 1.8″/44% | 3.8″/10% | 10 000 | 1625 | 6.15 |
| – | 1.58″/55% | 1.8″/36% | 2.8″/10% | 80 000 | 825 | 96.97 |
Notes. A fitting radius close to the maximum S/N is advocated by Stetson (1987) [Section III.D] in DAOPHOT, as well as Naylor (1998) (second column). A slightly larger radius is suggested by Mendez et al. (2010)[Fig. 4 in Section 3.2] (for astrometry, third column). As a reference, the last column is for a discrepancy tolerance of 10%. The first four rows are for a FWHM of 0.5 arcsec, the following four rows are for 1.0 arcsec (panels a to d in Fig. 1), while the last four are for 1.5 arcsec.
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