Bruno Sicardy et.al. (ERC Lucky
Star project, l'Observatoire de Paris) and IOTA-ES
(pro-am collaboration) request amateur observers in the UK to monitor
this prediction involving the total occultation of 16.3 magnitude star
in Pisces: UCAC4 474+000226 at altitude/azimuth of 35/141 on September
8th centered at 2304 30s +/- 13 sec UT. The Moon is setting.
recording time is 2302 to 2307 UT. The maximum event (D-R) duration
is 10 sec. A 40 to 70 cm appeture has been suggested and 1 sec cadence
Chiron is one of the Centaurs, otherwise classified as 95P/Chiron,
the most distant minor planet at the time of discovery in 1977 and believed
to be a comet with an Aphelion of 18.9 AU, and orbital period of 50
next star occultation is over the British Isles on 2019 Sept 08 at 2304
UT, when the shadow is predicted to cross Northern England and Scotland.
The uncertainty indicates that observers anywhere in the UK should attempt
to observe. It will be a challenging observation so planning and test
runs are suggested. It should be interesting! The probability of recording
an occultation (due to prediction errors) is 39%.
Please report all recordings.
Predicted shadow and centre
line. Some observatories are marked.
Invited observatories ( List under development )
Planned observations ( test
runs and other factors allowing...)
Sherwood Observatory, (Mansfield
and Sutton AS)
West Park Observatory, (Leeds),
The Amateur Astronomy Centre, ( AAC,Todmorden)
University of St Andrews
University of Central Lancashire (uclan)
S Kidd (Stevenage)
Isle of Man AS
lucky-star project need many more chords to improve the shape profile
of this minor planet. A time accuracy (exposure) of 0.5 to 1 sec should
provide new data. Of more interest is the search and detection of rings
or possible satellites. This will require a time resolution (exposure)
of the order of 100ms. Ring detection may require a 50 to 80cm class
instruments and dark skies.
amateur can contribute with 30 to 40cm, are the chord information (duration
of occultation) from widely spaced positions across the path. Video
cameras such as the integrating WAT-910HX would be ideal, but any mono
camera could be used. Larger CCD/CMOS cameras should be operated in
binning mode (e.g. 2x2 or 3x3) to obtain a plate scale near 1 arcsec/pixel
(typical). Some experimentation prior to the event will be needed. Please
check the PC clock time is correct to within 50ms of UT prior to recording,
30-40cm SCT, F 3.3 reducer,
50 to 70cm
Newonian. RC etc.
Drift Scan (untested by the writer)
Observing / recording
Obtain some test sequences on the star field days/week before under
good conditions to check detection, and become familiar with the setup.
We assume the observatory will have some light pollution, and SQM 20
may be typical (20 mag/arcsc2).
Check the PC clock is synchronize
to UT via NTP, or some other means. Make a note of any offset before
and after observation.
Focus the camera
Goto the star.
Use binning and/or
sub-frame to optimise detection and cadence.
Check there is at least one other brighter star in the field of view
to monitor seeing condiions.
Prepare to record from 2302
to 2307 UT at 1 frame per second, or adjust for best detection.
1) Use a focal length that matches the detector pixel size. We should
aim for a star image that fills one pixel. Due to changes in seeing
stability the star image can fluctuate between 1 and 3 arcseconds in
size. The image should be oversampled a little bit, but not a lot. Using
my 30cm F/4, the plate scale with a video camera of 8.5x8.5um pixels
is 1.5 arc sec. (good)
A 40cm SCT with F3.3 reducer
and same video camera gives 1.3 arcsec/pixel
A 40cm F/8 RC and ATIK 314L+
produces 0.4 arcsec/pixel. This is a bit too small, and CCD 2x2 binning
would improve sensitivity and lower the image size Kb and improve cadence.
2) Focus. A basic requirement
and so important. Get good focus at the centre of the field using software
or a mask, or use the diffraction spikes of a bright star.
3) Reduce light pollution.
Not easy. Local lighting can be nuisance, even inside the observatory.
Unsure of this, but a mono USB2/3 planetary camera has greater bit depth
(10 - 12 bit) compared to analogue video (8 bit). This should give better
definition when looking with faint objects like this.
00h 10m 13", +04d 37' 05" (J2000)
magnitude 16.1 to 16.5 depending on spectral type.
0.3 degree field:
ALADIN Field. A cross marks the star.
General tips for observers / recorders:
1) Let the writer
know if you plan to observe and your location (even if you don't observe
in the end). occultations AT stargazer DOT me DOT uk
2) Please do observe even if you are outside the dotted line limits.
These observations may be negative or short duration.
3 ) Allow enough time to find the correct star. The asteroid will be
4 ) If you use a mobile telescope, make notes on its location so that
we can get its coordinates from Google Earth.
1) Where possible use a focal reducer to get F3.3 to F5 or
2) Download and install Dimension
4 software and use it to update the computer clock to +/- 0.05 sec.
( for NTP)
3) Use the camera software control to add the computer UT time stamp
to the frames. This can be done with SharpCap
and FireCapture (or other products).
4) Often there is a log file function. Use this to add extra info.
5 ) Select an integration time that records the target star. Use trial
and error to get best result beforehand. If unsure make a recording
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
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
Tim Haymes: occultations AT stargazer DOT me DOT uk
Assistant Director, BAA Asteroids and Remote Planets Section,
Member of IOTA/ES
[ PS: If you see any typos, drop me an email
thanks :-) ]
About occultations and this page:
This is a personal web page to support occultation observers. There
is a Yahoo! group: UKoccultations which observers are welcome to join.
An observation sent to the writer is checked and forwarded to the BAA
which will perform a preliminary analysis prior to submission to IOTA-ES
and for PRO-AM collaborations, to the designated data collector.
SkyMap pro 11 was used to present the path on the sky and the star fields.