Astrometric performance of the five major uranian satellites using a narrow-band Methane filter

Abstract

During ground-based observations of satellites near a bright planet, the satellite images are often affected by the planet’s halo, introducing significant uncertainty in their astrometric positions. To address this issue, we employed a narrow-band methane filter for observations of the five major Uranian satellites, which makes them easily discernible on CCD frames without requiring halo removal procedures. We systematically evaluated the astrometric performance of this Methane filter and compared it to that of the commonly used Clear and Cousins-I filters. Totally, the positional precision for most of the four brightest satellites is approximately 30 mas in both right ascension and declination, comparable to the Cousins-I filter and superior to the Clear filter. On the other hand, the faint satellite Miranda achieves a precision of better than 80 mas after image stacking in the methane band images. Based on our experiments, we recommend using the Methane filter for observing objects with an apparent visual magnitude brighter than 15, as it offers a sufficient signal-to-noise ratio (SNR) of approximately 55 within a reasonable exposure time of 200 s using a 0.8 m telescope.