| Author |
 |
 |
N | |
| Eggen & Sandage (1964) | photoel. | -0.02 | 0.04 | 173 |
| Sanders (1989) | photoel. | 0.01 | 0.05 | 225 |
| Gilliland et al. (1993) | CCD | -0.02 | 0.03 | 136 |
| Montgomery et al. (1993) | CCD | -0.01 | 0.05 | 967 |
| Kim et al. (1996) | CCD | -0.01 | 0.04 | 89 |
| Henden (2003) | CCD | 0.01 | 0.06 | 306 |
| Sandquist (2004) | CCD | 0.01 | 0.03 | 154 |