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(862) Franzia occults UCAC4 632-027606


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About this observation
Alex Pratt
Time of observation
20/09/2019 - 22:41
(862) Franzia occults UCAC4 632-027606
Observing location
C11 f/10 and f/3.3 focal reducer
Watec 910 video camera
IOTA-VTI GPS time inserter
OccuRec (recording)
Tangra and AOTA (reduction)
0.16s (4 integrated video frames)
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The mag 14.8 main belt asteroid (862) Franzia, 27 km in diameter, was predicted to occult a mag 13.1 star in Auriga on 2019 September 20. Observers within the 52 km wide shadow track could see a drop in brightness of 1.8 magnitudes for up to 1.7s.

My site was inside the predicted shadow zone with a 20.2% probability of success. The sky was clear and I recorded the brief disappearance of the target star, 1.12s in duration. The attached screenshot shows the analysis of the light curve using Tangra and AOTA.

    D  - 22 41 01.27 ± 0.08
    R  - 22 41 02.39 ± 0.08

The actual track of the occultation was very close to the prediction. There are no previous observations of any Franzia occultations listed in the Occult database. This single chord across the asteroid confirms it is at least 19 km in diameter and the Gaia position of the target star will give high-precision astrometry of the asteroid at the mid-time of the occultation.


astrotom925's picture

Hi Alex. Looking forward to your talk at Newcastle. I am tentatively looking into occultation work. Hopefully you can give me some tips and ideas.

A R Pratt's picture

Hi Tom,

Sure, we can discuss a few ideas when I come up to Newcastle. A video camera and GPS timestamps are sometimes called the 'gold standard' for occultation work, although good quality timings can also be obtained with digital imaging cameras - and you don't need a large telescope. See you next month on the 17th.


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