Re: asteroids

[Bill Dillon <bdillon@houston.geoquest.slb.com>]

Arne wrote:

> 
> I note that Jedicke and Metcalfe have an accepted paper for Icarus on
> "The Orbital and Absolute Magnitude Distributions of Main Belt Asteroids,"
> based on 4 years of data with the 0.9m Spacewatch telescope on Kitt Peak.
> They say that "the set of known asteroids is complete to about absolute
> magnitudes 12.75, 12.25 and 11.25 in the inner, middle and outer regions
> of the belt respectively."  The 'absolute magnitude' is the magnitude at
> opposition, in this case referring to the V filter.  So it sounds like there
> might be a few asteroids still to be discovered that are within the reach
> of the mark III systems.  (paper astro-ph/9801023)

Forgive me for dropping out of lurker space, but these "absolute"
magnitudes are NOT opposition magnitudes, but the magnitude the
asteroid would have if were 1 A.U. from the sun and 1 A.U. from
the earth.  The "absolute" magnitude appears in an IAU formula
as one of two constants that (with solar and earth distances)
allows you to estimate the V magnitude of an asteroid for a 
given time.

Paul Comba, perhaps the U.S. leader in amateur asteroid discovery
(well over 300 now) wrote an article in the "Reflector" about
his work.  He had an interesting table summarizing the brightness
of the asteroids he's discovered.  The majority were 18th magnitude
and fainter, and only a handfull were as bright as 16th magnitude.

That's not to say that TASS can't be valuable in catching earth-crossing
or approaching asteroids (or comets!).  But you'll have to go much
fainter than 15th magnitude to discover lots of Main Belt asteroids 
these days.

Regards,

Bill Dillon
bdillon@houston.geoquest.slb.com
http://www.geocities.com/CapeCanaveral/7477/