Dossier observations

Occultation d'une étoile par un astéroïde

Documents complémentaires à l'observation
de l'occultation de PPM46655 par Julia

 

Roland Boninsegna :

Merci pour ton observation. Quelques mots concernant l'aspect technique de tes images CCD. Si l'occultation se confirme, ton observation aura la seule qualite de confirmer d'autres occultations positives. En fait, pour etre franc, la camera CCD n'est certainement pas l'instrument recommande pour observer ces phenomenes. Une surveillance photoelectrique, video, visuelle aurait ete plus adaptee (resolution temporelle insuffisante). Par contre les images CCD sont bien adaptee pour l'astrometrie et verifier si l'asteroide est bien passe "sur" l'etoile vu de ta position.

David Dunham :

Philippe,
Many thanks for your report of the occultation by Julia. It's good to know finally where the path really went. Sorry I couldn't reply sooner, since at the time of your message, I arrived in Turin, Italy, for a week-long meeting, and returned only late on the 12th, and am just now reading all of my e-mail at work. The problem with most CCD systems is that they are set up to integrate light over a relatively long time, making them unsuitable for timing occultations - it would have been better if, once the objects merged, you had used an eyepiece and look for a sudden disappearance and reappearance of the star, that you could have timed visually using a tape recorder to a few tenths of a second. I'm copying this to others who also tried to observe, but saw no occultation - your report is the first positive one. Jan Manek can reconstruct the path from your observation, and perhaps then we can contact others who might have observed the occultation.
David Dunham, IOTA.

Jan Manek :

Hello David and others too,
I have prepared chart showing where the path of October 3 occultation by (89) Julia most probably went. Attached you can find chart (color version O89.GIF, gray scale O89G.GIF) produced by OCCULT. The path was fitted to
all observations known to me (5) with listing following (+ indicates positive +? dubious positive, - negative observation):
Long , Lat , Place
-------------------------------------------------------
4.3706 , 50.9353 , Grimbergen (MIRA, Phillippe Mollet) -
14.47 , 35.913, San Gwan (Stephen Brincat)-
-0.1 , 53.2 , Lincolnshire (Paul Money) -
1.58 , 48.4 , Chartes (Philippe Martinol) +
11.0278 , 43.7 , Montelupo (Maura Tombelli) +?

The only true positive observation is fully filled circle (Martinol), the crossed circle is dubious observation on station 108 (Tombelli). The path surely didn't went more to SW as indicated by Brincat's negative observation on Malta. Occultation duration was reported to be 10 - 20 seconds. I prefer the shorter duration and placed his station to the south limit.

If this path is true, then it moved over Roma, Torino, Bern, Paris, Dublin and barely missed London. If you check the charts please contact other observers (even those not having e-mail) in the regions where it should be observed - Ireland, SE U.K., France, SW Switzerland and Italy. It may be possible they didn't send their reports yet.

Carte :