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skysurfer
sage


Reged: 10/05/09

Loc: NL, N 52 E 6
Is prediction occ. Regulus by 163 Erigone in 2014
      #4634269 - 06/11/11 04:38 PM

According to many sources on the internet (incl Wikipedia) there will be an occultation of the star Regulus by the very faint asteroid Erigone on 2014 March 20 from a narrow 40km strip which will pass over downtown NYC.
The image from Wikipedia:


When I downloaded the most recent orbital elements for Stellarium, I found that the asteroid will have its closest approacht om Mar 16 about 1/2 degree apart.
According to SkySafari (updaqted minor body database), the closest approach is on March 19, als falf a degree apart.

How do these guys get differnt orbital elements and are these predictions true ?


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Centaur
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Reged: 07/12/04

Loc: Chicago
Re: Is prediction occ. Regulus by 163 Erigone in 2014 new [Re: skysurfer]
      #4634340 - 06/11/11 05:30 PM

The source of the Wikipedia occultation path illustration is Aldo Vitagliano through the use of the Solex numerical integration software which he created: http://main.chemistry.unina.it/~alvitagl/solex/ . I use Solex data as an aid to my occultation calculations. Your other sources likely utilize osculating orbital elements which are only good for short periods of time around a base epoch. I have confidence in Aldo’s prediction for the event you describe. In Jean Meeus’ More Astronomical Astronomy Morsels chapter 29, Aldo provides generalized data for this event and other occultations of stars by asteroids.

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Centaur
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Reged: 07/12/04

Loc: Chicago
Re: Is prediction occ. Regulus by 163 Erigone in 2014 new [Re: skysurfer]
      #4634362 - 06/11/11 05:43 PM

It should be noted that Aldo Vitagliano requested attribution be made for redistribution of his copyrighted illustration of the occultation path that appears in Wikipedia: http://en.wikipedia.org/wiki/File:Erigone_Regulus_path.png . At least I supplied that in my reply to the OP. I'm afraid that simply crediting “Wikipedia” is insufficient.

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skysurfer
sage


Reged: 10/05/09

Loc: NL, N 52 E 6
Re: Is prediction occ. Regulus by 163 Erigone in 2014 new [Re: Centaur]
      #4635014 - 06/12/11 03:51 AM

This image is published on the internet for everybody, so it is free to redistribute if one provides the copyright hoder / source.
And that is what I did.
It is distributed on more sites,check google.


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Centaur
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Reged: 07/12/04

Loc: Chicago
Re: Is prediction occ. Regulus by 163 Erigone in 2014 new [Re: skysurfer]
      #4635426 - 06/12/11 11:49 AM

Quote:

This image is published on the internet for everybody, so it is free to redistribute if one provides the copyright hoder / source.
And that is what I did.
It is distributed on more sites,check google.




Please thoroughly study the text found after clicking the link I provided in my previous post: http://en.wikipedia.org/wiki/File:Erigone_Regulus_path.png . On that webpage the true copyright holder, Aldo Vitagliano, requests attribution. Wikipedia is not the copyright holder. People who work hard to provide a free service for other people at least deserve attribution. Repeating the carelessness of others is not justification.

Was the explanation of orbital determination methods in my first post helpful to you?


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Aldo Vitagliano
newbie


Reged: 06/12/11

Re: Is prediction occ. Regulus by 163 Erigone in 2014 new [Re: skysurfer]
      #4636604 - 06/13/11 06:32 AM

Quote:


...
How do these guys get differnt orbital elements and are these predictions true ?




Short answer:

You can trust the image linked by Wikipedia, whose original (drawn three years ago) is on my website here:
http://chemistry.unina.it/~alvitagl/solex/occpath2.gif
at least within the uncertainty estimate given by the red bars crossing each spot.
Note that time is given as UT.

Long answer:

The prediction of an asteroidal occultation track is delicate issue: an error of one arcsecond in the position of the asteroid, at the distance of 1.18 AU (the distance of Erigone at the moment of the occultations) means an error of about 850 km in the corresponding position of the “umbra” on the Earth’s surface. Therefore a very accurate prediction of the asteroid’s orbit is necessary, which cannot be obtained by common planetarium software. As Curt pointed out, these programs usually compute asteroidal positions by using the current osculating elements and simple Keplerian orbits, with no planetary perturbations taken in account. The method gives accurate positions only for epochs that are close in time (within a couple of months) to the epoch of the osculating elements, but at a time distance of about three years the error can be of several arcminutes.

On the other hand, Solex “propagates” all the orbits (including those of the major planets) by using a N-body numerical integration algorithm, which means that all the mutual planetary perturbations, and those affecting the motion of minor bodies are fully taken in account, thus making long-term predictions easy and reliable. In addition, the software provides some ways of estimating the uncertainty of a prediction, which I consider even more important than the prediction itself.
Just to be on the safe side, I have now determined the orbit of (163) Erigone, by using only the observations made in the last 14 years, and recalculated the occultation paths from a number of possible “clones” of the asteroid created by the orbit determination procedure. All the results fit the path given in the image, within the uncertainty given by the red bars. So I am pretty confident in the accuracy of the prediction.

Turning to copyright issues, I am not particularly eager to be cited as the source of published data, especially in an informal discussion board such as a Forum (more important it would be in a book or magazine). Nevertheless I would certainly appreciate it as a form of courtesy and politeness.

Best regards, and greetings to all forum members
Aldo Vitagliano


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skysurfer
sage


Reged: 10/05/09

Loc: NL, N 52 E 6
Re: Is prediction occ. Regulus by 163 Erigone in 2014 new [Re: Aldo Vitagliano]
      #4637157 - 06/13/11 02:42 PM

i downloaded Solex and tried it in Windows 7 and XP but it is missing a DLL.
Anyway thanks for your (and Centaur) answers.


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Aldo Vitagliano
newbie


Reged: 06/12/11

Re: Is prediction occ. Regulus by 163 Erigone in 2014 new [Re: skysurfer]
      #4637172 - 06/13/11 02:56 PM

Very strange. There is no DLL missing.
Two DLLs: GFXT_PRO.DLL and CT_PRO.DLL should be in the same directory where the executable file SOLEX110.EXE is located.
Check this out ...
A.V.


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NadirZen
newbie


Reged: 01/16/13

Re: Is prediction occ. Regulus by 163 Erigone in 2014 new [Re: skysurfer]
      #5627716 - 01/17/13 09:53 AM

You may have downloaded only the latest executable; you need to download file: SETS110L.ZIP
After installing, you may want to replace the file SOLEX110.EXE with the one contained in the SOLEX110.ZIP (which you probably have).
SOLEX is a very impressive and interesting program.
R.L.


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