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OOF Holography package
User's Manual
Bojan Nikolic
July 26, 2001
Abstract
The Out-Of-Focus (OOF) Holography package attempts to calculate
inaccuracies of the surface of a telescope from a set of observations of an
astronomical object taken at dierent focus settings. It has been designed
as an extension of John Richer's Holography system (this manual will
assume some familarity with that environment). The OOF holography
package has been implemented in the programming languages C++ and
TCL.
1 Introduction
The OOF package has been designed so that the user can work with it
entirely from within TCL. The user interacts with the package in the
following three ways:
 The oof TCL command provides an interface to the C++ portions of
the code. Individual functions are selected by passing subcommands
to the oof command. On-line help is available via the command oof
subcommands.
 A number of TCL variables provide a way of controlling numerous
aspects of the behaviour of the package as well as providing input
and output of data.
 There also exist a collection of TCL procedures and scripts which
provide a number of useful features and allow consistent and more
comfortable work.
Before attempting to use any portions of the OOF package it is essen-
tial to run the oof init command. This loads and initialises the remain-
der of the package, so making sure that any impact on existing holography
scripts is minimised.
2 The oof command
The oof command provides an interface to the C++ portion of the oof
package. It is always used in conjunction with a subcommand, so the cor-
rect syntax is oof . The following
subcommands are available.
1

init Initialises the oof subsystem, creates global variables and arrays.
Note that the oof init commands reads the defaults le initparams.tcl,
and creates the suфcient number of slots for number of Zernike co-
eфcients specied there. Therefore, the maximum order of Zernikes
required in a session should be specied there.
currentf Reads the current parameterisation from oof ic and returns
a [eld2] representing the surface errors (phase) and illumination
(amplitude).
fsurface .... Fits a surface to
the supplied maps. The mask should contain 0 at bad values. When
the command returns, the calculated best t surface parametrisation
is stored in the oof ic array and a field2 representing the surface
is returned.
beam chop Uses the current parametrisation in oof ic to
predict what a chopped beam map would look like, defocused by
the given amount.
beam scuba Uses the current parametrisation in oof ic to
predict what a doubly dierentiated (chop+nod) beam map would
look like, defocused by the given amount.
print Prints out the current surface parametrisation in an easier-to-read
format
3 Variables
The behaviour of the OOF package is controlled mostly by three arrays:
oof pars, oof ic and oof fit. These arrays can be manipulated in the
standard way:
 Their contents can be listed by typing parray
 Individual element can be inspected by typing puts $()
 Individual elements can be set using set $()
 Arrays oof pars and oof ic additionally have a pair of helper com-
mands, oofset and ooficset, which simplify the setting of elements
in respective arrays. Their syntax is oofset .
3.1 The oof ic array
The oof ic array contains the complete current description of the model
describing the telescope: it contains information on the shape of the sur-
face, the illumination pattern, any chopping parameters and receiver spe-
cic information such the mean level of maps.
When tting a surface to a set of data maps, the contents of oof ic
is used as the initial guess of the surface, and the new optimum surface
description is stored in the same array. Information contained in oof ic
can be stored and read in from les, see oofsave and oofload.
A short description of elements of the array:
z0 ... zn Coeфcients of Zernike polynomials, normalised so they repre-
sent radians at the edge of the telescope dish. z0 refers to the piston
term, z1 to the n = 1; l = 1 term, z2 to the n = 1; l = 1, z3 to
the n = 2; l = 2 and so on. These coeфcients completely describe
the phase variation across the surface.
2

amp is the amplitude of the illumination.
x0,y0 describe the center of the illumination pattern, in units normalised
so they are 1 at the edge of the dish.
r,rho,di The illumination taper is modeled using a 2D Gaussian func-
tion: exp [r(x 02 + y 02 ) + rho(2x 0
y 0 ) + diff(x 02
y 02 )], where x 0 =
x x0 and y 0 = y y0 and all distances are normalised to be unity at
the edge of the dish. The ratio of r to rho and diff is a convenient
measure of how isotropic the illumination patter is.
hchop,vchop Are the magnitudes in arcseconds of the chop movement,
in horizontal and vertical directions.
hnod,vnod Are the magnitudes in arcseconds of the nod movement, in
horizontal and vertical directions. Only relevant if a doubly dier-
entiated beam pattern is used, eg. SCUBA.
dicoma Is the dierential comma term produced by the chopping of the
secondary term, normalised so it represents radians at dish edge.
mean Is the mean of the model maps.
3.2 The oof fit array
The oof fit array species which parameters dened in the oof ic should
be tted for and which should be kept xed. For each element in oof ic,
there is an element of the same name in oof fit. If the value of the
element is 1 then that parameter is a free parameter should be tted for,
while if it is 0, it should remain xed.
By default, all parameters other then z0 are tted for. The z0 terms is
omitted because it represents a uniform phase change across the surface
of the telescope and the beam map is invariant under this transform.
3.3 The oof pars array
This array contains a large number of parameters which control what sort
of tting should be attempted, details about the geometry of the telescope
and other data. The most important elements are described bellow.
mapsize The size of maps (in pixels) to be used throughout. Only square
maps are supported at the moment. Using mapsize which is not a
power of two has not been tested.
pixelsize Species the size of each pixel in arcseconds.
zorder Use Zernike polynomials of orders up to and including zorder.
This parameter can not be changed during a session: to change edit
the initparam.tcl le and restart.
sn The signal to noise ration in supplied data maps. Used in calculating
the correct  2 .
noise Additive noise present in supplied data maps. Used in calculating
the correct  2 .
observ lambda The wavelength in meters at which the beam maps were
made.
primary diameter The diameter of the primary mirror (dish) in meters.
foc bigf, foc smallf Focal lengths of in meters of, respectively the pri-
mary and secondary mirrors.
3

method Select the minimisation algorithm to be used in the tting pro-
cess. It is recommended this is set to 3, which selects the Levenberg-
Marquardt algorithm.
ftol Species the fractional tolerance which the minimisation algorithm
should try to achieve.
scubachop If this is set to 1 then the doubly dierentiated maps will be
made. This already includes the chopping of the secondary mirror,
so simplechop should be set to zero. Normally, this option is used
for analyzing maps taken with SCUBA.
simplechop If this is set to 1 then model beam maps will include chop-
ping of the secondary mirror. Otherwise should be set to 0.
4 TCL commands and scripts
oofsave Saves the contents of the oof ic array to the spec-
ied le. Very useful for storing surface parametrisations for later
use.
oo oad Restores a surface parametrisation from specied
le.
readmap Reads a map in from the specied le. This com-
mands is suitable for use with simple ASCII les as produced by old
Rx A data.
tsio read 1 Reads a map in the standard ts format | as
produced by SCUBA reduction software.
oofmask