Diapositiva PPT
Effectively we need stars over the full range of magnitudes from 0 ? N ? 15, although most stars will be at the middle of this range.
- N=7 ? s/n?200-300 in 100s in broad-band.
- We need very bright stars for the highest resolutions. To get the same s/n at ?????1500 requires a star 6 magnitudes brighter than for broad band.
- The faintest stars are needed for instrumental verification by observatory staff - can we trust a 5? detection at faint magnitudes?