Update re. star to be occulted
TONIGHT:
The following measurements indicate a combined
(star+comet) magnitude of 14.56R, and that a total occultation will induce at
least a 2.2 mag drop in brightness as measured in a 3" radius photometric
aperture. Smaller measuring apertures (dependent on seeing and good focus) would
see an even larger decrease in brightness.
Richard Miles
BAA
-------------------------------------------------
COD Z21
OBS LCOGT
MEA R. Miles
TEL 0.40-m
f/8 Schmidt-Cassegrain + CCD
ACK MPCReport file updated 2020.12.08
10:14:51
NET UCAC-4
STAR_aa C2020 12
07.97031 02 18 09.60 +25 19
05.1
14.70R Z21
STAR_aa C2020 12 07.97187 02 18 09.59 +25 19
05.0
14.71R Z21
STAR_aa C2020 12 07.97342 02 18 09.60 +25 19
05.1
14.72R Z21
STAR_aa C2020 12 07.97498 02 18 09.60 +25 19
04.9
14.72R
Z21
0029P C2020 12 07.97031
02 18 27.37 +25 21 54.8
16.74R
Z21
0029P C2020 12 07.97187
02 18 27.35 +25 21 54.5
16.81R
Z21
0029P C2020 12 07.97342
02 18 27.32 +25 21 53.7
16.75R
Z21
0029P C2020 12 07.97498
02 18 27.30 +25 21 53.8
16.83R Z21
----- end -----
----- Original Message -----
Sent: Monday, November 30, 2020 4:52
PM
Subject: [comets-ml] Rare Stellar Occultation Event
involving Centaur comet 29P/Schwassmann-Wachmann 1
> In the late evening of Tuesday 8th December 2020, the 64-km
nucleus of Comet
> 29P/Schwassmann-Wachmann 1, along with its inner coma,
are predicted to
> occult a 14th magnitude star in the constellation
Aries as seen from Russia,
> Finland, Sweden, Norway, UK and Ireland. The
star will be favourably placed
> high in the moonless sky as seen from
the UK.
>
> The path crosses Scotland about 23:24 UT and so in this
case (and for other
> parts of the UK) the recommended observing window
is 23:21 to 23:27 UT. For
> Sweden, the times will be about 1 minute
earlier.
>
> The position of the magnitude 14.7R star involved is
R.A. 02h 18m 09.6s,
> Dec. +25° 19' 05".
> The expected maximum
duration of the occultation by the nucleus is 5.0 s but
> there is good
reason to believe that secondary events involving a partial
> dimming of
the star may also be seen if a debris disk or shell exists
> embedded
within the inner coma. The most likely times for secondary events
> are
within 60 seconds either side of closest approach. Similarly,
>
observations from locations up to 1000 km or so from the nominal shadow
>
track may detect partial dimming of the star.
>
> As far as I know,
this event will be the first opportunity to probe the 29P
> system by the
occultation method. Telescopes of 25-cm aperture or larger
> (the larger
the better) together with a sensitive integrating video camera
> are
recommended. Alternatively if you wish to try using an integrating CCD
>
or CMOS camera then the drift-scan method would be especially useful for
> detecting possible fades caused by debris shells or rings.
>
> Importantly, 29P exhibits occasional strong outbursts and so the
nucleus is
> usually embedded in a faint coma. Good seeing and good
telescope focus will
> be important in detecting any changes in the
intensity of the starlight
> throughout the long observing window. The
last strong outburst of 29P was on
> November 25th and the pseudonucleus
has been fading since that time. If no
> further outbursts happen over
the next 8 days then we should be in for a
> fairly unobstructed view of
the pseudonucleus of the comet.
>
> Josselin Desmars of the Lucky
Star Team
> (https://lesia.obspm.fr/lucky-star/index.php) and Mike Kretlow of CORA
> (Collaborative Occultation
Research on Asteroids) have independently
> generated predictions for
this event. Thank you both!
> Mike's predictions are now available online,
where you can click on the path
> dots and get information such as the
predicted time in an info popup. See:
> https://astro.kretlow.de/occpred/occ/342050/ (Mike's latest)
> https://astro.kretlow.de/occpred/occ/342021/ (JPL-H)
>
> Please report positive and negative
observations to:
> UKoccultations@groups.io
> planoccult@ls.vvs.be
>
> Clear skies all and good luck,
> Richard Miles
>
BAA
>
> P.S. Please consider distributing this alert to others,
such as local
> astronomy groups in the countries involved, who have
suitable equipment to
> observe this event. Thank you.
>
>
>
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