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Re: (V=8.7 m) 27 2007 .
« Ответ #30 : 24 Сентябрь 2007, 17:05:19 »


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Re: (V=8.7 m) 27 2007 .
« Ответ #32 : 24 Сентябрь 2007, 17:10:55 »
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Re: (V=8.7 m) 27 2007 .
« Ответ #35 : 24 Сентябрь 2007, 17:38:13 »

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Re: (V=8.7 m) 27 2007 .
« Ответ #36 : 24 Сентябрь 2007, 17:39:37 »

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Re: (V=8.9 m) 27 2007 .
« Ответ #37 : 25 Сентябрь 2007, 13:20:24 »
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« Ответ #38 : 25 Сентябрь 2007, 19:45:59 »
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[IOTAoccultations] New prediction shows possible occultation of SAO 160793 by Charon on Sept. 27

David Herald, Canberra, Australia, has updated his prediction of the
Pluto/Charon appulse on Sept. 27, using a new Pluto ephemeris including currections from
recently observed occultations, including the one by Pluto observed from the
western U.S.A. on March 18. This shows the southern limit of the occultation
by Charon just grazing the Earth over Mongolia and south-central Siberia.
With the remaining uncertainties, an occultation by Charon lasting over 100s
is possible between 14:55 and 15:10 UT of Sept. 27, for observers in
western China, Mongolia, and southern Siberia, with some chance also a little
farther south, from central Asia to southern China, and even possibly
northern India. He sent some maps and charts that I'll post on my Web site at
http://iota.jhuapl.edu/pluto.htm later today, but they might be posted first
at some of the other Pluto occultation Web sites.

David Dunham

, :

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[PLANOCCULT] Occultation of 8.7-mag. star by possible rings of Pluto this week

Hello,

FYI, I put some maps of the 27 Sept. 2007 events (Pluto and Charon) on my
page:

http://calys.obspm.fr/~sicardy/predic_occn_06_07/table.html

go to the bottom of the page ("Section 2 - star astrometry based on 1.6m
and 0.6m LNA telescopes/Brazil"), and click on "Pluto" or "Charon" cases
in the light-blue table

The event is mainly visible low above horizon from Ausralia, Indonesia,
Asia, China and India, and higher above horizon, but in evening twilight,
from Pakistan, Afganistan, Iran, Irak (...), Saudia Arabia, La Reunion

Cheers,

Bruno
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[PLANOCCULT] Occultation of 8.7-mag. star by possible rings of Pluto this week

>From J. Lecacheux

Hi all,

About the incoming exceptional Pluto / SAO 160793 appulse, Aleksey Losyuk asked:

> When it is necessary to begin photometry of of occultated star and when to finish it?

1/ By analogy with major planets, we could hope a main ring existing
well inside the orbit of Charon, the innermost satellite of Pluto.
The orbital radius of Charon is 19 400 km.

According to the current prediction by the MIT, based upon the UCAC2
position of "P507"= SAO 160793 and recent USNO astrometry of Pluto,
the closest approach should occur near 14:48 UT on Thursday 27 at
7 700 1 100 km above the Pluto surface.
This is well inside the Charon orbit, as roughly midway between Pluto
and Charon.
Nevertheless such an appulse at about 7.5 equatorial radii from Pluto's
center might be not close enough, leading to a miss of the ring.
(Something really difficult to forecast, as we don't know what this
hypothetical ring would be like...)


2/ Faint diffuse rings, narrow ringlets, discrete arcs, etc. also could
exist in the region of the outer satellites Nix and Hydra.

Assuming the MIT appulse prediction, I have computed the approximate
GEOCENTRIC instants of the orbit crossings by the beam from the star:

- Star entering the HYDRA  orbit       :    13:43 UT
- Star entering the NIX    orbit       :    14:01
- Star entering the CHARON orbit       :    14:37

- Closest approach of the star at 0".39:    14:48 UT
- Crossing the Pluto-Charon line       :    14:55

- Star leaving  the CHARON orbit       :    15:13 UT
- Star leaving  the NIX    orbit       :    15:48
- Star leaving  the HYDRA  orbit       :    16:07


These geocentric times are valid also from Uzbekistan.
ADD 1-3 mn from India, 2 mn from La Réunion and Mauritius, about 6 mn
from south-east Asia, 8 mn from west Australia.
The uncertainty probably lies under 5 minutes.

In my opinion any complete monitoring should begin near 12h30 UT,
if possible from the site (for example from Australia), i.e. at about
75 equatorial radii ESE from Pluto, and should end near 17 h (for
example from South-Africa), at the same distance WNW.


3/ Sure, other faint rings could exist even very farther, maybe at 400
equatoral radii as pointed out by David, but seeking them would consume
two or three complete nights, undoubtly with a low chance of detection.


4/ Some other useful informations to prepare this observation :

The velocity relative to Earth of the Pluto system will be 11.1 km/s
or 0.49 mas/s. This seems favourable, as occultations by Pluto often
are faster.
(Note : 1 mas = 1 milli-arc second will correspond to 22.82 km at the
current Pluto distance).

The probable apparent diameter of the giant target star should be close
to 0.5 mas or 11 km.  (Note : I assumed a K4 III star at 400 parsecs).
The Fresnel diffraction scale will be 1.1 km in visible light or 2.3 km
for 2.2 microns (infrared) sensors.

It results that any quick event (for example a brief occultation by
some "Uranian-style" narrow ringlet, or by some "Neptunian-style" arc)
will be lengthened to about one second by the stellar diameter.
Besides
- the occultation drop will suffer reduction,
- any diffraction effect should be almost erased.

To be able to detect by further image addition the slow crossing of
a faint tenuous ring of very small optical depth, please take the
following precautions :
- keep in the field of the camera the brighter SAO 160798, abput five
  arc min. east (a V= 8.0, R= 7.8 white-yellow subgiant star);
- to beware of any signal saturation, either by this bright comparison
  or by the red target itself.

Note1 : This above suggested bright comparison star is a close visual
binary where one component is a magnetic variable star. Its luminosity
period is unknown, but probably equal to the star rotation. Moreover
Hipparcos found only a 0.011 mag. scatter from 57 widely time-spaced
measurements. So one may assume the magnitude of SAO 160798 will not
vary at few minutes scale, thus it can be used as reliable comparison
along the Pluto event.
Note2 : Some fainter comparisons within 0.1 degree also are convenient
for large telescope users.

Good luck to every observer.

, :

, J. Lecacheux , 12:30 17:00 UT.

! , :

David Dunham, J. Lecacheux, Bruno Sicardy,

SAO 160793.

.

1. V=8.7 m [target star] SAO 160793 UCAC2, . ( ) The Tycho-2 Catalogue (Hog+ 2000) : V=8.945+/-0.033 m, B=10.351+/-0.058 m, (B-V)=1.406 m.

2. Dave Herald wrote:

> Attached are plots of this event, with a correction to the DE413 position of -100mas and
> +60mas having been applied (as consistent with recent occultations).

Majdanak (MPC code 188, longitude 66deg 53' 47.0'' E, latitude 38deg 40' 23.7'' N, altitude 2575 m), 14:48, 14:51 UT. 15:02.

3. http://www.referat-s.ru/mathematics/26405 .

( ) 60 - , 7.8 .

: Perov N. I. A method of localization of unknown minor bodies in multiple systems of major bodies / Proceedings of International Conference "AstroKazan-2001", September 24-29, 2001, Kazan State University: Publisher "DAC", 2001. P. 253-256.

Rylkov V. P., Vityazev V. V., Dementieva A. A. Pluto: an analyses of photographic positions obtained with the Pulkovo normal astrograph in 1930-1992 / Astronomical Transactions. 1995. V. 6. P. 265-281.

, . 2510-2520 , Rr.

3700 . 5.5 (14:51 UT). 5.5 .

4. , 160798 , [target star] SAO 160793. The Tycho-2 Catalogue (Hog+ 2000) : V=8.0380.017 m, B=8.5040.018 m, (B-V)=0.466 m.

. , , . [target star] ( ) , .

14 15 UT Majdanak 32 27 .

, CCD .

5. .

, 1977 .

. Lupus abstract Nature http://nssdc.gsfc.nasa.gov/planetary/factsheet/uranringfact.html ( http://www.ka-dar.ru/forum/index.php/topic,702.msg7511.html#msg7511 ). , 0.109 m (t=0.1) 0.543 m (t=0.5).

t - ( ) , , ( , ).

6. Bruno Sicardy, http://calys.obspm.fr/~sicardy/predic_occn_06_07/table.html 2007 . , .

DE413? Dave Herald:

> Fairly soon I will be releasing a new version of Occult - in beta form. A key improvement for events
> involving Pluto is that the DE413 ephemeris can be downloaded for the predictions. DE13 was
> generated a couple of years ago specifically for Pluto occultations. The path location is _significantly_
> different from the DE405 ephemeris. Indeed, for Pluto occultations DE413 is effectively mandatory.

, Dave Herald (as consistent with recent occultations). .

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Re: (V=8.9 m) 27 2007 .
« Ответ #39 : 25 Сентябрь 2007, 23:23:19 »
http://www.referat-s.ru/mathematics/26405http://nssdc.gsfc.nasa.gov/planetary/factsheet/uranringfact.html executed an indirect estimation of value of magnitude falling (look http://www.ka-dar.ru/forum/index.php/topic,702.msg7511.html#msg7511). He has shown, that magnitude falling for rings of Uranus was from 0.109 m (optical depth of ring t=0.1) up to 0.543 m (optical depth of ring t=0.5).

Here t - the optical depth of media, the dimensionless value describing the attenuation of optical radiation in the media at the expense of joint action of light absorption and dispersion (but without effects of amplification of the radiation caused by multiple dispersion).
We haven't access to "Nature" articles, and we cann't to compare this resuts. So, maybe Vitaly is mistaken in his calculations

6. Dear Bruno Sicardy, we watched closely for your page http://calys.obspm.fr/~sicardy/predic_occn_06_07/table.html during all first half-year 2007. Unfortunately, in the second half-year you have ceased to make calculations of stars occultations by Pluto and its satellites.

Do you use ephemeris DE413 during the calculations of Pluto occultations? That writes Dave Herald:

> Fairly soon I will be releasing a new version of Occult - in beta form. A key improvement for events
> involving Pluto is that the DE413 ephemeris can be downloaded for the predictions. DE13 was
> generated a couple of years ago specifically for Pluto occultations. The path location is _significantly_
> different from the DE405 ephemeris. Indeed, for Pluto occultations DE413 is effectively mandatory.

Besides this, Dave Herald considers, that it's necessary to note the correction for this ephemeride (as consistent with recent occultations). About it it is written above.

Best regards,

Losyuk Alexey



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Re: (V=8.9 m) 27 2007 .
« Ответ #40 : 26 Сентябрь 2007, 00:15:10 »

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Re: (V=8.9 m) 27 2007 .
« Ответ #42 : 26 Сентябрь 2007, 21:18:38 »

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Re: (V=8.9 m) 27 2007 .
« Ответ #44 : 27 Сентябрь 2007, 08:10:49 »