TIPS ON ASTROMETRY

Astrometry

Everybody reads this page (i.e. has got a PC connected to the Web) and owns a telescope with a CCD camera can virtually start measuring the position of asteroids and comets, which is called astrometry: the more those measures are accurate (less than one arcsec), the better the orbit of the celestial body is known, and this is very important for asteroids and comets which approach the Earth's orbit or are targets of spacecrafts.
Astrometry indeed is one of the fields where amateur astronomers can collaborate with professionals at the same level, and this is evident in the official reports known as Minor Planet Circulars prepared by I.A.U., where single amateurs and the world most famous astronomical sites like E.S.O., Kitt Peak, Siding Spring, etc. publish their observations together (see below...)
abstract MPC

The same instruments used in astrometric work could be employed in asteroid hunting: the methodology is to compare two images of the same part of the sky taken with a 30 min. interval, and look for not-in-catalogue objects which have moved.
If the further observations allow to calculate the orbit with the sufficient accuracy, the people who have discovered the new celestial body will have the privilege to name it as they want.

In the two frames the asteroid (433) Eros has moved slightly during half an hour interval: images taken at Grange Observatory on the evening of Sep. 15th, 1995 with CCD Electrim EDC-1000 HR, 90 s exposure.

What's needed for the astrometric activity:

the subscription to the Computer Service of Minor Planet Center to access directly the major database on asteroids and comets;
the astrometric program can measure the CCD images;
the stellar catalogue used by the above program is on-line at STScI;
the software for the accurate timing turns the PC erratic clock in an observatory reference time source;
the photographic plates taken at Mount Palomar Obs. for the all-sky survey are retrievable at POSS site: the stellar limit magnitude is about 21. Very useful to check if the CCD image just taken is the right one or not;
the IAU's "Guide for Minor-Body Astrometry" is on-line here.
an image processing sofware will be very useful, too.
Some good software useful for astrometry can be found in Project Pluto's and 670 Camarillo Obs.'s sites.
If you're interested in asteroid appulses to stars or deep sky objects, consult the Minor Planet Observer; other interesting data about asteroids are in Asteroid Node site.

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