Asteroid occultation, 30 September 2015

On the morning of Wednesday 30 September 2015, between 04:27 – 04:30 UT, the +13.9 magnitude asteroid (275) Sapientia will occult the +7.9 magnitude star HIP 14977 in Aries.

The star is well placed at an altitude of approximately 42º in the south west. However, there is a 93% illuminated Moon only 13º away and so equipment needs to be shielded from any lunar glare. The star will disappear if an occultation from your location is observed. The maximum duration for the event, should you be lucky enough to observe it, is expected to be 18 seconds yet if you are away from the centre line of the path, the duration could be considerably shorter.

The path chart I produced put the path across the centre of the country but predictions on the internet put the path further south. As with all asteroidal occultations, negative observations are just as important as positive ones and they can show if the path has shifted. Information gained from asteroidal occultations contributes towards details on the asteroids orbit, shape and size. Please be aware that during these events, keep watching even after the event has taken place as there could be a second occultation if the asteroid has a natural satellite.

To observe the event you will need reasonable equipment, binoculars probably won’t be ideal for this observation, depending upon magnification. Ideally a driven scope is better, one less thing to worry about while looking down the eyepiece. It would also be wise to locate the star well before the event and so not to become flustered nearer the event time.

Timings are important too. You will need a stopwatch with lap time function and a reliable time source eg a radio controlled clock. As soon as the star disappears, start your stopwatch. On reappearance stop it on lap mode, make a note of the time (the duration of the event) and continue. Stop the watch against a set time with your reliable time source.

Deducting the time off your stopwatch from the set time will give you the time the event started.

Report forms for asteroidal (and lunar) occultations are downloadable from the SPA website:

More information and star charts for the occultation are available from here:

Here are star charts showing how to find the star, produced using SkyMap. The first one shows the general area while the second one shows a close-up of the area within the yellow rectangle, with black stars on a white background suitable for printing out. The star itself is shown within a small square.

Good Luck and Clear Skies

Mell Jeffery, FRAS

Occultation Section Director