Elgin Observatory
HOME

ASTEROID OCCULTATIONS
Asteroids frequently eclipse stars.
Such eclipses are called occultations.
Not quite so frequently an observer may be in a place to measure the occultation.

Measuring an asteroid occultation can provide good astronomical information.
Primarily, an observation can give some information as to the size of the asteroid.
If several observers measure the same occultation, the profile of the asteroid can be determined.

Also, the occultation light curve might be able to determine if the star being eclipsed is a double star,
or possibly find that the asteroid has a satellite.

Finally, measuring an occultation provides information on the location of
the asteroid's orbit and can refine the position of a star.
    See - Asteroid Occultation Methods & Resources
    and
    Check out John Broughton's web site for detailed instruction
    on using drift scan to record occultations


    To measure an occultation with a CCD camera (Drift Scan)
    one takes an extended exposure with the telescope tracking turned off.
    This gives a "drift trail" for each of the stars in the image.
    The occulted star's trail will have a break or reduction in brightness
    as the star is occulted.

    Once the image is obtained a program that can measure a spectrum is used
    to measure the drift trail. I use AIP4Win or Vspec, both work fine.

    The essence of measuring an asteroid occultation is getting accurate timing.
    John Broughton's web page covers this in detail.
    For SBIG camera's there is a new tool for timing.
    CCDOps-5.55 can connect to a Garmin GPS18x-USB unit.
    This allows CCDOps to mark the beginning and ending time
    of an exposure accurate to better than 0.01 second.




HOME