----------------------------------- UFO 18 Ian 2012 10:53 ----------------------------------- Gareth V. Williams FROM Minor Planet Center, EXEMPLU DE RASPUNS. An accurate orbit, one that would allow you to do a direct recovery at the next opposition, requires accurate observations over (usually) an arc of at least 60 days. Getting accurate positions from photographic plates is very time consuming and error prone. Most photographic positions during that era were approximate or semi-accurate (the one accurate position that Demetrescu made was a visual observation with a micrometer--another error prone method). Even if he had accurate measures of all his plates, he would still have had an arc of only ~30 days. By Dec. 3 the object was 1 magnitude fainter than at discovery and 0.5 mag fainter than on Nov. 1. It is unlikely that he could have followed it much longer than he actually did. And it is probable that a new object will be fainter at the next opposition--(1189) was 0.5 mag fainter at the 1917 Jan. opposition--making it harder to find. In addition, consideration of planetary perturbations was a monster undertaking, generally undertaken only for a handful of well-observed object (and even then, undertaken in a way that today we would consider merely an approximation). Predictions for the next opposition of a one-opposition object would be done without consideration of perturbations. For a giggle, I ran an orbit with the 1915 observations and predicted where the object would be in Jan. 1917, ignoring perturbations: it was off by > 20 deg. in R.A. and > 9 deg. in Decl. from where (1198) really was. It is not a question of competence. It's a question of available resources and techniques. CCDs make observing today easy. Computers make orbit computations today easy. This was not the case in 1915... so... Multumesc MPC pentru lamuriri. Aroganta lui Alex denota lipsa de respect pentru orice (in primul rand cititori). Probabil ca aceasta deranjeaza cel mai mult. ALEX : In concluzie: - Demetrescu nu a determinat o orbita nici macar aproximativa a acelui obiect, a trebuit sa vina un alt individ in 1932, sa faca link intre masuratorile din 1930 si 1932 pt a gasi o corelatie mica cu una din pozitiile lui Demetrescu. Greseala fatala nr. 1, din care rezulta un intreg lant de erori care au dus la invalidarea observatiilor. - Demetrescu nu poate fi considerat descoperitor, avand in vedere ca nu a facut aproape nimic util pt asteroidul ala. - Demetrescu intra in categoria de observatii precovery, cu cea mai veche observatie cunoscuta pana acum la acel obiect (cum ziceam mai sus, nu au fost digitizate toate arhivele fotografice ale altor observatoare pt a vedea daca exista sau nu alte pozitii mai vechi). Sa inteleg ca tu puteai sa calculezi orbita ? In zilele noastre si un copil de 15 ani poate face asta cu un pc, insa acum 100 de ani, nu erau pc-uri. Totul era facut pe hartie. Da, acum o sa prinzi prilejul sa te lauzi din nou, arogant. Nu ma mai uimeste nimic din ce scri. Ai o ura inexplicabila pentru Demetrescu. Cred ca tine de patologie. :shock: