Comet
29P/Schwassmann-Wachmann 1
Occults TYC
1888-00333-1
2023 May 07 @ 2242-2245 UT
TEST on 2023-04-19.9:
FITS image of a star of similar brightness and spectral type: The star
was at Alt/Az 13.3 / 298 and the instrument a C11. But the telescope aperture
was partly obscured (50% area) by the observatory wall at this low elevation.
The equivalent aperture was calculated as about 20cm.
An SER file was also obtained to measure Signal/noise (SNR) with Tangra
Full info:
QHY174-gps, 100ms exposure, 20cm aperture, TYC 1918-1836-1 B-V 0.3, mag
11.7, SNR 5.
Sky conditions: good, SQML 20.85 (zenith).
Image: 0.3 degrees
TEST
on 2023-05-01.9
FITS images of the target star TYC 1888-333-1 obtained in Moonlight: Image-1
is 2 sec exposure to obtain an approximate r magnitude using Astrometrica.
Camera and settings: C11 at F5.8, QHY174-gps, 2x2 bin, gain 300. SharpCapPro
with anti-banding reduction. T=-10C, un-calibrated.
Image-1. The
star is magnitude r 11.7 (unfiltered CCD)......................Image-2
exp 200ms (gain 360) through thin cloud when star at altitude
15deg (C11).
. 
CONCLUSION: With an 8 to 10" it should be possible to image at 5 or even 10 fps in poor transparency, using a mono camera (bin 2x2) at medium gain.
Below: Image-3 of the star field (10x2sec stack) when at altitude 29deg in clear Moonlit conditions. Comet 29P is outside the area.
Observations received as of 2023-05-15
Owen Brazel (Farringdon)...clouded...............................................
Jennings used a 20cm Newtonian, WATEC-910HX video camera at 2 x frame
integration (0.08s, 12.5fps) in clear conditions. Timing with GPS-VTI
onto AVI (DivX compressed).
This is the first confirmed UK observation of a comet nucleus occulting
a star (Lucky-Star team prediction.)
Observed light curve (blue) relative to a brighter field star:
A Provisional SkyPlane plot for the reported observatons, relative to a default circular profile fitting the observation. (T Haymes with Occult4 software )
Observerations relative to the updated ground track (M Kretlow) in Collaborative Occultation Rescources and Archive (CORA) [ opens a new page ]
Background to the campaign:
A rare opportunity to see a star occulted by this comet [Fig-1] can be followed by UK observers on the evening of 2023 May 07. The star: TYC 1888-00333-1 is relatively bright at visual magnitude 11.7 and will be situated low in the West at 13-14 deg. altitude and azimuth 297.
M. Kretlow and R. Miles established a revised orbit for 29P. They used
astrometry of the pseudo-nucleus while it was in a quiescent state (no
cometry coma). The ephemeris is being used by JPL and the ERC LuckyStar
group to predict occultations by this large (>60km diameter) comet
[1]. An occultation chord will provide constraints
on a shape profile for the nucleus which cannot be observed directly [2].
[1]
https://lesia.obspm.fr/lucky-star/occ.php?p=122512
[2] Kretlow
and Miles:
Occultations by 29P https://www.iota-es.de/JOA/JOA2021_3.pdf
Observing Aims
Observers in or near the predicted path [ Fig-2 ] are invited to observe the star as the comet passes. The aim is to record the time (UT) and duration if the star is occulted. Typically this can be recorded by a planetary video camera using the computer clock synchronised to UT (or BST). Suggested techniques are explained later see TIPS (new page). An unobstructed horizon to the west is needed. A mobile telescope might be required to reach the star. Advance planning is recommended !
Please report
all observations, even though no event may have occurred.
Occultation
Details:
Date: 2023 May 07 at 22:43:15 UT +/- 15 sec
Observe/record from: 2242 - 2245 UT ( 2342
- 2345 BST)
The
Maximum occultation duration is 2.0s
Occulted
star : TYC
1888-00333-1 (in
Gemini)
Colour index:
B-V = +0.25 (spectral type F)
Equatorial coordinates (epoch
J2000.0, ICRS)
RA: 06h 40m 53.4s
Dec: +26° 51' 43.5"
Combined magnitude R 11.5
(assumes the comet is not in outburst)
Magnitude
drops to about 16 (magnitude of the quiescent pseudo nucleus)
Fig-1, Path of the shadow displayed by Occult 4 software.
Fig-2
Shadow path displayed on a map:
Green line: line of maximum duration, Blue
line: edge of the predicted shadow, Red
Line: edges of the uncertainty regions
Fig-3 View of the star field (Sky Map Pro) of about 1degree: The occulted star is in the white square.
Tips for observers / recorders:
1.
Planning:
1 ) Observe if you can, even
if you are outside the red line limits in Fig-2.
These observations may be negative or short duration.
2 ) If you use a mobile telescope, then note the location so that we
can get its coordinates from Google Earth.
3 ) Take test exposures of the star when at about 15-20 deg altitude
some time before.
4 ) Check that the horizon at +13 / 297 is unobstructed !
5 ) Use SER or FITS files, with an exposure between 0.1 and 0.3 s (conditions
allowing) or shorter.
MORE tips HERE
Experienced observers should submit reports to SODIS and the Lucky Star occult-portal in the usual way.
Send
preliminary reports or notifications to: Tim Haymes: tvh DOT observatory
AT btinternet DOT com, or to the UKoccultations.group.io
And copy reports to Richard Miles: rmiles AT baa.u-net DOT com
Page prepare by Tim Haymes: Assistant Director (Occultations), BAA Asteroids and Remote Planets Section.
About the occultation 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 above
contact by email is acknowledged, checked and forwarded to the British
Astronomical Association (BAA) which will perform a preliminary analysis
prior to submission to IOTA-ES
or the LuckyStar research group. Further
information from observers may be requested by email.
Acknowledgements:
Occult-4 software by Dave Herald was used to compute the prediction
using orbital data from the sources indicated.
OccultWatcher and OccultWatcher Cloud services by Hristo Pavlov are
used to present the ground maps for planning observer locations.
SkyMap pro 11 was used to present the star map and finder field.
This page was created: 2023 April 19