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(71) Niobe occults UCAC4-660-030215

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About this observation
Observer
Alex Pratt
Time of observation
10/02/2019 - 18:52
Object
Asteroid (71) Niobe occults star UCAC4-660-030215
Observing location
Z92
Equipment
C11 f/10 and f/3.3 focal reducer
Watec 910 video camera
IOTA-VTI GPS time inserter
OccuRec (recording)
Tangra and AOTA (reduction)
Exposure
0.08s (2 integrated video frames)
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The magnitude 12.3 asteroid (71) Niobe, 82.5 km in diameter, was predicted to occult a mag 11.8 star in Aur in the early evening of 2019 Feb 10. Lucky observers who were within the shadow track could see a drop in brightness of almost 1 mag for up to 6.9s.

My site was 2.5 km outside the predicted track but I was fortunate that the shadow moved slightly to the west and I recorded a dip in brightness for 3.80s as the asteroid occulted the star. The attached plot shows the analysis of the light curve using Tangra and AOTA. (Reprocessed, giving a smaller uncertainty for the D).

D     18 52 39..33 +/- 0.04

R     18 52 43.13 +/- 0.04

An extract from the video can be viewed here. (The clip was converted from OccuRec's AAV format to AVI then to WMV, but it illustrates the event).

The occultation was successfully monitored by other observers in England and continental Europe and their timings, chords and the overlaid shape model are available on Euraster.

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