(814)Tauris (possible binary): 2020-Jan-26


A recent occultation by this 108km diameter asteroid observed in the US, indicates a possible binary structure or some exaggerated relief like a crater. The Journal for Occultation Astronomy [1] (JOA), describes the observations in detail and the theory put forward to explain a double (full extinction) occultation recorded by Drift Scan [2]. One chord was obtained.

More observations are requested.

The next occultation is over the British Isles on 2020 Jan 26 at 05:26 UT, across England.

[1] JOA 2019_3 http://www.iota-es.de/joafree.html
[2] Drift scan Timing by John Broughton http://www.asteroidoccultation.com/observations/DriftScan/Index.htm

Observing Aims

More chords will improve the shape profile of (814)Tauris. The paper in JOA lists the events where chords were obtained in the past. Five predictions, but no more than 2 positive chords in any one event. The asteroid is most likely a rotating object so the profile may be time dependant. Rotation light curve observations in the ALCDEF [3] database indicate only a small magnitude differential of about 0.1 mag and no clear light curve.

[3] http://alcdef.org/


Occultation prediction for Tauris:
Prediction made on 2019 July 11th

Occulted star : UCAC4 403-066026 ( GSC 5630-511) in Ophiuchus
Magnitudes: v 12.9, r 12.0
Magnitude drop: 3

Maximum duration 3.9s


Finder field of 5 degrees:

Finder field of 0.5 degrees

Tips for observers / recorders:

1. Planning:

1 ) Please observe even if you are outside the dotted line limits. These observations may be negative or short duration.
2 ) If you use a mobile telescope, then make notes on its location so that we can get its coordinates from Google Earth.

2. Planetary Cameras:
1) If possible use a focal reducer to get F3 to F5 or thereabouts. This usually applies to SCT
2) Download and install Dimension 4 software and use it to update the computer clock 10min before the observation
3) Use the camera software control to add the UT time stamp to the frames. This can be done with SharpCap and FireCapture (or other products).
4 ) Select an integration time that records the target star clearly without over-exposure.
6) The integration time (or exposure) is likely to be 0.1 to 0.5sec. The shorter the better, but this will depend on your telescope and sky clarity
7) Record in the format (SER or AVI) which shows the time stamps clearly.
8) Observe/record for a minimum of 3min around the predicted mid time.
9 ) Use a clear filter, or no filter.
10) The desired UT accuracy is +/-0.1 sec

3. Video cameras
1) Record analogue video in AVI format using a USB-2-digital converter (e.g. Pinnacle) and VirtualDub software, or possibly Sharpcap (untried).
2) Introduce time onto the video frame during recording with a GPS Video Time inserter if you have a VTI such as GPSBOXSPRITE or IOTA-VTI

Note how you time the occultation in a written log book.

4 Reporting:
1) The observer should play back the file and note the approximate times of any events. A software analysis will be needed to extract the exact times.
2) There is a free software tool (TANGRA) if the observer does the analysis, otherwise send the file to the writer for analysis (drop box, wetransfer etc).
3) Negative result (no occultation) are as important as the positives. Please report negatives or "unsure".
4) There is standard report to fill out. Contact me if you have a successful recording.

Good luck...

Tim Haymes

Tim Haymes: occultations AT stargazer DOT me DOT uk

Assistant Director, BAA Asteroids and Remote Planets Section, Occultations.

[ PS: If you see any typos, drop me an email thanks :-) ]


More information:

About occultations and this page:
This is a personal web page to support occultation observers. There is a discussion group https://groups.io/g/UKoccultations which observers are welcome to join. An observation sent to the writer is checked and forwarded to the British Astronomical Association (BAA) which will perform a preliminary analysis prior to submission to IOTA-ES.

Occult-4 software by Dave Herald was used to compute the predictions. Nearer the time, an update may appear from Steve Preston (IOTA)
OccultWatcher software by Hristo Pavlov is used to present the ground maps for planning observer locations when these become available.
SkyMap pro 11 was used to present the path on the sky and the star fields. .

Page created: 2019 July 11