Elara, or Jupiter VII

Elara at 02:45 UT Elara at 04:05 UT

Elara is the eighth largest Jovian satellite and has a diameter of about 87 km. Elara was magnitude 16.6 at the time of observation.

The two images were taken 80 minutes apart and very clearly show the motion of Elara. The earlier image shows the satellite to the right of a distinctive line of stars, second-lowest of which is notably fainter than the others. The later image reveals a 18.4-magnitude background star, the light of which had been completely drowned out by the much brighter satellite. By this time Elara had moved so close to a star of similar magnitude that the two objects are not resolved and they now appear as a single object which is about as bright as the other three stars in the line.

When these images was taken Jupiter and its satellites were located within a dense portion of the Milky Way in Ophiuchus, which explains why there are so many stars of comparable or greater brightness in the image.

Image information
Date and times of observation  2019-06-20 02:45 and 04:05 UT
Telescope 0.4m f/6.5 Dilworth-Relay
Camera Starlight Xpress Trius-PRO SX814 CCD
Filter None
Exposure 1×10s+10×60s and 18×30s, each median-stacked
Centre of image RA 17h10m49.6s  Dec -22°51'49"
Image dimensions 5.2 arcmin × 5.6 arcmin