John Mahony wrote: > --- David Nicholls <[EMAIL PROTECTED]> wrote: > >>So that means CDC will only accept the first 99999 asteroids in >>astorb.dat, because all higer numbers use 6 digits? > > > No, the problem only affects the numbered asteroids. Asteroids only get > numbered (and named, if the discoverer is interested in naming it) after > they've been observed long enough that the orbit is well enough known that > there's little chance it will get "lost". That typically takes a few > opposition cycles, or typically around 5 years. > > Before that, the asteroid is known by a "provisional designation" that looks > something like "2003 TK47". There are over 300,000 known asteroids, but the > number with permanent numbers only just passed 100,000.
The astorb.dat file is a bit bewildering for the newbie. In my case I'm only interested in viewing the occasional asteroid, not in serious observations, so editing the extra space from the beginning of each line for the first few hundred meets my needs, but I was curious about how far the editing had to go if CDC is to read the entries correctly. >>In practice one would probably only ever want to identify the named >>asteroids, and these number around 25000. > > > 12779, as of December 15. Yes, you're right. I scanned through astorb.net until there were no more named asteroids, but in fact there are many gaps where they aren't named. > But I disagree with your premise. I'm one of many amateurs making follow-up > astrometric (position) measurements of newly discovered near-earth asteroids, > to help refine the orbits of these objects. I use CdC to help locate the > objects and point the scope, for CCD imaging. > And then there are events like the close pass of 2000 NY40 in November 2000, > which was so close you could watch the asteroid move in real time in the EP. That's impressive testimony to the effectiveness of CDC as a research tool. > If you're looking for one or a few objects that aren't in the short "bright or > unusual" list, and you don't want to deal with the full astorb file, you can > get a customized file of asteroid elements from > <http://cfa-www.harvard.edu/iau/MPEph/MPEph.html>. Thanks for that. > Enter the objects you want, skip the middle portion, then under "format", > select "TheSky" (same format that CdC uses). It will download a file called > "elements.txt", which you can either cut/paste to append into your current > asteroides.dat file, or just rename it to replace your old file (in the > ciel/cat/planet folder). > > You can do the same with comets, and the "cometes.dat" file. Thanks. Very useful information. DN -- ____________________________________ David Nicholls Nicholls Communications http://www.dcnicholls.com/ ____________________________________ ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/1.XolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/skychart-discussion/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
