All the FITS headers on ArcVIEW-generated images must be described on a header file template. This template specifies the order, names, comments and where to get the values (or the actual values if they are fixed ones). If using multiple extensions fits file images, then it can be described a diferent set of keywords for each extension (if desired).
ArcVIEW reads the template file, and at the moment of generating the image it will add the specified keywords, taking the current values of the variables from the specified source.
symbols used on this document
< >: denotes a requiered field
[ ]: denotes an optional field
Header file template
The header template is just a list of ascii lines, where each entry corresponds to a keyword:
KEYNAME1='<expresion>' /[comment]
expresion : corresponds to the source where
to get the value, or the value itself. Possible values are:
database
: Get the value from the internal ArcVIEW database. This is the
most usual source
datatype <value>: Will take "value" and will add it according
to the datatype specified. If not datatype specified, it will assume "STRING".
Datatypes
can be: U32 (ULONG), U16 (UINT), U8 (BYTE), I32 (LONG), I16 (INT), I8 (SHORT),
FLOAT, DOUBLE, STR (STRING),
where U: unsigned, I: signed. FLOAT is 32 bits, DOUBLE is 64 bits.
file <path>
: Get the specified file and append it to the headers.See the explanation
below
comment
: the comment that will appear on the correspondent keyword
An example of header file template is:
OBJECT ='database
' /object title
SOFTVER ='database
' /software version
HDR_REV ='database
' /header revision
OBSERVER='database
' /observer
UTSHUT ='database
' /UT shutter open
EXPTIME ='database
' /exposure time (secs)
NAMPSYX ='database
' /number of amplifiers in y x
CCDSUM ='database
' /binning in x y
GEOMETRY='database
' /FPA geometry
TCSINFO ='database
' /info from the TCS
FILTINFO ='database
' /filter position/ID
COMMENT ='database
' /any comment
CCDTEMP = 'FLOAT 112.5 '
/celcious degrees
ANYKEY = 'any
comment' / if no datatype specified, it will
be added as string.
FILEINFO ='file <expresion>'
/appended file header
/*see explanation on this field below*/
The Keyword names that appear on the header template must be valid ones (listed at the end of the document) in order to be recognized by the database. In other words, if you want the time in which the shutter was opened you MUST add a "UTSHUT" entry; however, if you want it to appear with a diferent name on the headers, you can specify a diferent name in this way:
OBSTIME@UTSHUT = 'database ' /any comment you want
This format is saying: "write OBSTIME instead of UTSHUT for the
time when the shutter was opened".
Any value available on the database can be written to the headers;
a complete list of the currently available database variables is
given in the "DBS Keywords document"; note, however, that the list may
be expanded, as requiered, at any time.
Special Keywords
FILEINFO
sintax: FILEINFO = 'file <expesion>'
/[comment]
Specifies a file or a set of files with extra information to be added
to the headers. The value of <expresion> can correspond to an
specific file or to multiples ones using wildcats. The filepath must
be absolute . Examples are:
a) FILEINFO = 'file /home/ArcVIEW/ConfigFiles/weather.hdr'
FILEINFO = 'file
/home/ArcVIEW/ConfigFiles/temperatures.hdr'
In this case the content of both files will be added to the headers. The specified files must follow the rules mentioned above for file templates (even when this files are expected to normally have only fixed values updated by an external application)
b) FILEINFO = 'file /home/ArcVIEW/ConfigFiles/*.hdr'
In this all the files with an "hdr" extensions will be read an added
to the headers
TCSINFO
The Keyword noted as "TCSINFO" it is only saying "add the info coming
from the TCS, whatever that info may be".
All the information coming from the TCS can be added to the headers;
however, this info is usually customized by editing an Info template file
for the specific TCS in use. See the TCS info header file template document.
Some usual TCS keywords are DATE, TIME, RA, DEC, FOCUS,
AIRMASS, etc
GEOMETRY
The Keyword "GEOMETRY" it is saying "add the keywords which describes
the geometry of the array". Currently the only set of keywords provided
is an iraf-like one. In the future there will be more modules for
making specific or customized descriptions. A complete description of these
keywords exists on the "NOAO-Mosaic Geometry keywords" document
UTSHUT
The UTSHUT keyword is provided by ArcVIEW, and it is computed at the
moment in which the controller opened started the exposure. Since the TCS
normally returns its own observation time, the headers usually have two
time keywords (or three if the fits file creation time is added). The
diference between these two times will depend on the communication
delay between the camera software and the TCS.
UTSHUT has the following format: YYYY-mm-ddTHH:MM:SS.msmsms
where
YYYY : four digits year
mm : two
digits 01-12 month
dd
: two digits 01-31 day
T
: standard date-time separator
HH : two
digits 00-23 hour
MM : two digit 00-59
minutes
SS
: two digits 00-59 seconds
msmsms : three digits 000-999 milliseconds
The value should have a precision of about 2 ms relative to the local
host time (which is synchronized, through an NTP daemon, with the
GPS clock).
Multiextension Images
If a multiextension fits format is used, then it is possible to specify
a diferent set of keyword for each extension, using the following convention:
[<expresion1>]
Keywords
....
[<expresion2>]
Keywords2
.....
where expresion can be:
number
: extension number
/*add to extension number all the keywords specified untill the
next [ ] expresion*/
number1-number2: from extension number1 to extension
number2 /*add the next keywords
to all extension between
number1 and number2*/
number1-*
: from extension number1 to the end
/*add the next keywords to all the extensions from number1 (inclusive)
to the end*/
*
: all the extensions
If no <expresion> (neither brackets) is given, the specified
set of keywords will be added to all the extensions of the image.