Themisto was discovered in 1975 and promptly lost until 2000. It is a rather small body, only 9km in diameter, and never gets brighter than 20th magnitude.
In the image above, Themisto is indicated by cross bars. The arrow points at Gaia EDR3-6771111466513671680 which is catalogued at g=20.66. Themisto itself was magnitude V=20.3 when this image was taken.
| Date and time of observation | 2020-09-05 22:40 UT |
| Telescope | 0.4m f/6.5 Dilworth-Relay |
| Camera | Starlight Xpress Trius-PRO SX814 CCD |
| Filter | None |
| Exposure | 1708s in 31 subs. |
| Centre of image | RA 19h17m02.5s Dec -22°44'50" |
| Image dimensions | 3.9 arcmin × 2.2 arcmin |