Precision premium, a concept in astrometry that was firstly presented by Pascu in 1994, initially means that the relative positional measurement of the Galilean satellites of Jupiter would be more accurate when their separations are small. Correspondingly, many observations have been obtained of these Galilean satellites since then. However, the exact range of the separation in which precision premium takes effect is not clear yet, not to say the variation of the precision with the separation. In this paper, the observations of open cluster M35 are used to study precision premium and the newest star catalogue Gaia DR2 is used in the data reduction. Our results show that precision premium does work in about less than 100 arcsecs for two concerned objects, and the relative positional precision can be well fitted by a sigmoidal function. Observations of Uranian satellites are also reduced as an example of precision premium.
Observing dwarf planets and other large Kuiper Belt objects (KBOs) from vantage points between 8 and 47 au from the Sun, NASA’s New Horizons spacecraft has found diversity in the shapes of their solar phase curves. Here we extend solar phase angle coverage of dwarf planets (136199) Eris, (136472) Makemake, and (136108) Haumea; large KBOs (28978) Ixion, (50000) Quaoar, (307261) 2002 MS4, and (556416) 2014 OE394; and Neptune’s satellite Triton to phase angles as high as α = 94° using New Horizons data and fit the resulting solar phase curves to the Hapke photometric model. When accounting for sparse α sampling, these fits yield large uncertainties in the Hapke parameters; however, opposition effect parameters are generally well constrained and suggest a significant range of regolith maturation ages among these bodies. The expanded range in α enables evaluation of Bond albedos, phase integrals, rotation curves at high α, and comparisons of the surface scattering properties of these objects with those of others in the solar system. The dwarf planets with surface compositions dominated by hypervolatiles, Eris and Makemake, and Triton (a likely former KBO) have shallower solar phase curve slopes (i.e., lower phase coefficients, higher phase integrals, and Bond albedos) than objects with volatile-poor surfaces. The total amplitude of Haumea’s rotation curve at α = 48° is Δm = 0.6 ± 0.2 mag, nearly twice that of its rotation curve measured from Earth at low phase angles. Bond albedos range from 0.037 ± 0.007 for Ixion to 0.99 − 0.09 + 0.01 for Eris.
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