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Ocultatie cu planeta pitica Haumea in 21 ianuarie


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ovidiuv
Membru
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Data inscrierii: 30 Mai 2013
Mesaje: 159



Localitate: Santa Cruz de La Palma

MesajTrimis: 11 Ian 2017 13:40 Download mesaj
Titlul subiectului: Ocultatie cu planeta pitica Haumea in 21 ianuarie
Raspunde cu citat (quote)

Salut Grup,

Am primit din Granada urmatoarea invitatie pentru Romania
la observarea (si publicarea impreuna cu colegii astronomi de acolo)
unei ocultatii cu TNO-ul Haumea, cea mai buna metoda pentru stabilirea
marimii (inca destul de nesigure) a acestui obiect.

Este posibila cu telescoape mici (~40cm) echipate cu camere CCD,
CMOS, foto digitale sau camere video (posibil si web?). Va avea loc
in noaptea de 20 spre 21 ianuarie, in speranta ca vremea se va imbunatati.
Anuntul mai jos si trei harti atasate. Daca aveti intrebari, il puteti contacta
direct pe colegul Pablo (in engleza sau spaniola) sau eventual pe mine
(desi nu prea am timp de asta acum).

Marian, te rog sa te inscrii pe lista SARM@Yahoogroups (care nu necesita
apartenenta la asociatia SARM), unde eu trimit stiri astro pentru RO.

Ovidiu

---------

From: Jose-Luis Ortiz <ortiz>
Date: Tue, Jan 10, 2017 at 5:35 PM
Subject: IMPORTANT stellar occultation by Haumea on January 21st at
around 2:10 UT
To: sbnaf_team@mpe.mpg.de

Dear all,

As you probably know, Haumea is the only dwarf
planet for which a stellar occultation has not been recorded yet.
Detecting an occultation would allow us to determine its size and
shape to kilometric accuracy. Besides, Haumea is a very exotic
body (a fast rotator and a very elongated body for its size). And it
has two satellites. Even though its surface is covered mostly with
water ice, we cannot discard that there could also be other more
volatile ices that might give rise at least to local atmospheres,
which would also be detectable through an occultation.

Hence we might expect intersting science and a very high-impact
publication if we succeed in the observation.

We have been working very hard to predict and update this occultation.
We initially predicted it more than a year ago and we have been
collecting quite a lot of data to make an accurate update (because as
you know, the angular accuracy of the ephemeris of all TNOs are far
more uncertain than their angular diameters... Hence updates are
critical to succeed).

It turns out that updating the stellar occultation by Haumea with
recent high quality astrometry is not as direct as we have done it for
other TNOs. The reason is the presence of the large satellite Hiiaka,
which is bright enough to cause periodic oscillations in the
optocenter of the Haumea system, with the period of the orbit of the
satellite (49.2 days). The amplitude of this oscillation is also much
larger than the angular diameter of Haumea!.

We noticed this oscillation from a large data set that we obtained in
April-July last year with our 0.77m telescope at la Hita, comprising
more than 1000 measurements spread along several months.

In the last few weeks we have obtained Haumea images with 5 large
telescopes and have worked hard, but so far we are still struggling
with getting the correct phase of the photocenter oscillation to come
up with an accurate prediction of the position of the shadow path.

Using all the data sets my current best guess is the attached map.
However, I still cannot discard a more eastward and a more westward
shadow path (see the other two attachments).

In the next few days we will get more data and I expect we will be
able to reach a more precise prediction. So currently the best
approach is to try to set up observations from as many observatories
as possible from Turkey to Spain. So we encourage you to arrange
observations from your observatories and contact colleagues who might
be willing to participate in this campaign.

The star that will be occulted is magnitude 17 so telescopes in the
~40cm size range are needed. We expect a drop of around 1 magnitude in
the flux of the combined star+Haumea. Because the occultation will
last longer than is usual for most TNOs (up to 110s in this case),
integration times of several seconds can still provide very valuable
results. Note that it is important to start observing at least around
15 minutes before the nominal occultation time (~2:10 UT) and finish
15 minutes after that in order to get a good baseline to characterize
the noise. Also note that computers should be synchronized with the
best time precision possible, using internet time servers or other
methods. No filters should be used to maximize the signal to noise
ratio, and it is also important to try to minimize the readout time of
the CCD camera either by using binning of by taking a window or a ROI
(Region Of Interest) of the CCD. Also try to keep at least one
reference star in the field of view to monitor transparency
fluctuations etc. If your readout time is, for instance, 1s, use
integration times of around 4s so that the percentage of time loss is
only around 25%. A common mistake by many observers is to use too
short exposure times; in these cases the risk of missing the ingress
or the egress of the occultation is very high and if the ingress or
egress are missed no reliable chord lengths can be determined, which
ruins the observations. So, in summary, the integration time and the
readout should be balanced. If your readout time is 1s use at least 4s
of exposure time, and if your readout time si 2s use at least 8s of
exposure time.

If you plan to observe please keep Pablo (psantos@iaa.es) informed.

Best regards,
Jose-Luis



2017 Jan 21 0 HaumeaJPL+182+84.jpg
 Descriere:
 Marime fisier:  114.52 kb
 Vizualizat:  de 640 ori

2017 Jan 21 0 HaumeaJPL+182+84.jpg



2017 Jan 21 1 Haumea JPL east.jpg
 Descriere:
 Marime fisier:  114.52 kb
 Vizualizat:  de 640 ori

2017 Jan 21 1 Haumea JPL east.jpg



2017 Jan 21 1 Haumea JPL west.jpg
 Descriere:
 Marime fisier:  112.33 kb
 Vizualizat:  de 640 ori

2017 Jan 21 1 Haumea JPL west.jpg



_________________
Cer senin!

Ovidiu
Sus
auriga
Membru
Membru


Data inscrierii: 22 Dec 2008
Mesaje: 1888



Localitate: Cluj-Napoca

MesajTrimis: 11 Ian 2017 15:21 Download mesaj
Titlul subiectului: Re: Ocultatie cu planeta pitica Haumea in 21 ianuarie
Raspunde cu citat (quote)

Cu un telescop mai mic se poate modificand putin viteza de urmarire si expunand cateva minute (astfel incat Haumea sa nu iasa din camp). In acest mod se poate observa momentul in care Haumea va scadea in magnitudine. Eventual se poate si masura cu o precizie mai scazuta. Se poate experimenta cu o stea de magnitudine apropiata pentru a determina viteza de urmarire optima.
Haumea va fi pe la 47 grade altitudine si 300 azimut, magnitudine 17.4V cu Luna iluminata 37% la doar 30 grade distanta.
Cu camere de viteza mare (gen Watec 902H) este nevoie de un telescop mare pentru aceasta magnitudine.
Sus
Mircea Pteancu
Moderator
Moderator


Data inscrierii: 12 Feb 2008
Mesaje: 5404

Motto: ''OBSERVO ERGO SUM''

Localitate: Arad

MesajTrimis: 11 Ian 2017 22:31 Download mesaj
Titlul subiectului:
Raspunde cu citat (quote)

Regret ca nu pot sa particip dar telescoape chiar asa de mici (pe la 40 cm ) nu am. Very Happy
Succes la observatii si sa ne spuneti si noua rezultatul,Mircea

_________________
http://observoergosum.blogspot.ro/
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