Observation by Alex Pratt: (862) Franzia occults UCAC4 632-027606

Uploaded by

Alex Pratt

Observer

Alex Pratt

Observed

2019 Sep 20 - 21:41

Uploaded

2019 Sep 23 - 08:44

Objects

Conjunction

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Constellation

Hydra

Field centre

RA: 10^h28^m
Dec: -17°23'
Position angle: +87°46'

Field size

2°14' × 1°11'

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

0.16s (4 integrated video frames)

Location

Z92

Target name

(862) Franzia occults UCAC4 632-027606

Title

(862) Franzia occults UCAC4 632-027606

About this image

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.

Files associated with this observation

2019-Sep-20 23-40-39 (272)_Bin1_Form.png (73.9 kB)

Like this image

David Swan, Ray Emery, David Basey, Neil Morrison, Jeremy Shears, Dean Ashton OBE, Graham Winstanley, Mr Leonard Entwisle, Andy Wilson, Martin Crow, Nick Hewitt, Ron Arbour, Dr Paul Leyland, Andrew Dumbleton, Peter Carson

Comments

Tom Moran, 2019 Sep 23 - 11:10 UTC

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.

Alex Pratt, 2019 Sep 23 - 15:02 UTC

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.

Alex.

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