From Thu Jul 3 11:53:56 2003 -0400
Date: Thu, 3 Jul 2003 11:53:55 -0400 (EDT)
From: Sam Ragland
To: "Wesley A. Traub"
cc:, Rafael Millan-Gabet ,,,,,, Mike Pearlman ,
gary wallace , Mike Brewer ,
Chip Coldwell ,,
Subject: Good News on Closure phase measurements

Hi All,

1) I find that the IOTA/IONIC provides stable closure phase
measurements - no appreciable day-to-day or run-to-run
drift in the instrumental closure phase.

2) Also, Chromaticity is not a serious issue. I find that the instrumental
closure phase changes very little with the spectral type - a maximum
of ~ 3 degrees between extreme spectral types (see the enclosed
figure: The left and right columns correspond to the two complementary
closing triangles)

3) At 1.75 microns, the complementary closing triangles has an offset
value of ~ 12 degrees.

4) The instrumental closure phase is a function of wavelength of
observations and PICNIC camera settings such as OPD range, number
of reads and loops.

I will post the details of my findings on our web site soon and write you the link.

Sam Ragland
Harvard-Smithsonian Center for Astrophysics (MS20)
60 Garden Street
Cambridge MA 02138
Tel: (617) 495-7158 (W) (617) 389-7461 (R)
Fax: (617) 496-0121/ 617 495-7467