Arecibo Observatory

Exercises related to the ALFALFA observing mode

Review the memo we wrote on ALFA beam rotation.

Suppose the ALFALFA schedule for a given day targets the drift at +28d35'30"; therefore, the central beam (designated Beam "0") is the one which is set to declination of +28d35'30".

  1. What is the zenith angle of this drift as observed with ALFA beam 0?
  2. At what azimuth will we orient the azimuth arm so that ALFA can observe this declination strip?
  3. List the resultant seven declinations covered by the seven beams, in order, from south to north.
  4. Assuming a mean effective HPBW of the telescope at 1.4 GHz (the frequency of the HI line) is about 3.5 arcminutes, how long does it take for a source to traverse the beam?

Last modified: Sun Oct 7 09:41:14 EST 2007 by martha