Introduction
The Telescope
& Optics
The
Detectors
The Imaging
Cameras
An Imaging
Cookbook
The Data
you Take Away
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times
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files
CCD
Windows
Data
Catalogs
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Shutters
NB: Some of the following discussion is irrelevant to direct CCD imaging. However, it is all included for completeness. Of the example files, numbers 4-10 are the most directly relevant to direct imaging.
A window is a rectangularly bounded region anywhere inside the data digitization area which includes the physical CCD chip and typically extends beyond it by a number of rows and columns in each direction. The hardware supports single and dual windows which may be placed anywhere in the digitization area.
The current software allows only dual windows, except for time series mode where only a single window is allowed. The present program also requires that the two windows begin on the same starting row and finish on the same end row. This restriction may be relaxed in later software. For normal readout mode, single windowing is simulated by defining either the left or the right window as a single column of the bias overscan region or by simply butting the two windows together.
For the purpose of binning the data, each window may be divided into one, two or three horizontal binning fields (summing columns). Both windows together may also be divided into one, two or three vertical binning fields (summing rows). The hardware currently requires that the vertical binning be the same for both windows, though the horizontal binning can be different.
In this appendix, we use the following terminology: A line is a single row of CCD pixels before binning and a row is a series of image data elements after binning. Pixels are individual detector elements on the CCDchip or their direct equivalent in the pre-scan or over-scan areas, BEFORE binning. Bins are the digitization or image data elements AFTER binning. For example, one row of 193 bins with a horizontal binning factor of 2 and a vertical binning factor of 3 corresponds to 3 rows of 386 pixels each on the CCD chip. Examples of window definitions, and the resulting data frames, are given in §5 below.
The default location where OBSERVER looks for windows is given by the value of the logical name WINDOW_DIR, which is currently given by
WINDOW_DIR = ADAMLOCAL:[WINDOW.R0_0]
= ADAMLOCAL:[WINDOW.Q0_1A]
ADAMLOCAL = DISK$USER:[SYSDISK1.ADAMLOCAL.]
If you are logged in as OBSERVER or NIGHT then WINDOW_DIR will be defined. It is not defined if you are logged in as OBSRED. Window files are sometimes also stored in DISK$USER:[OBSERVER], DISK$USER:[OBSERVER.WINDOW] and DISK$USER:[OBSRED], though OBSERVER must be given an explicit filename in order to read these files.
A called program PGWINDOW is provided to graphically examining these window files, when you log into the NIGHT account (your support astronomer will give you the password) on the VAX. Before you can run it, you must set the DECW$DISPLAY logical name, using the xon script.
40a> xon aatxtr
(replace
aatxtr
with the actual name
should be printed on the X-terminal or Sparc
station)
40a> pgwindow
PROGRAM : WINDOW
Function -
To display the information contained in the .WINDOW files
PGPLOT v4.9G Copyright 1993 California Institute of Technology
Graphics device/type (? to see list, default xwindows):
xwindows
Which detector [TEK]/GEC/THOMSON/RCA/UNKNOWN/quit ? TEK
What window file? (If your own specify disk as well as directory)
TEK1K_DIRECT_CEN
The ccd window you are using has been divided into
2 window(s).
--------------------------------------------------
Window number 1
this window is specified by the following pixels
X start X end Y start Y end
366 665 366 665
X bin factor 1
Y bin factor 1
--------------------------------------------------
Window number 2
this window is specified by the following pixels
X start X end Y start Y end
1029 1050 366 665
X bin factor 1
Y bin factor 1
As well as displaying the numerical values of the window, the program will display the window layout in a PGPLOT X-window, which should look like this example.
Vertical binning means combining CCD rows. If the whole frame is to be binned in the same way, there is a single vertical binning field called the middle field. It is also possible to split the CCD window into two or three sub-windows (binning fields), with different binning factors.
If there are two vertical binning fields, the first is called the first field and the second the middle field. These may have different vertical binning factors. If there are three vertical fields, they are called the first, middle and third fields. The third field will have the same binning factor as the first. The vertical binning field possibilities are:
Horizontal binning means combining CCD columns. If there is only one horizontal field in the window, it is called the centre field
If there are two horizontal fields, the first is called the left field and the second the centre field - this may have a different horizontal binning factor from the left field.
If there are three horizontal fields, the first field is called the left field, the second is called the centre field and the third is called the right field. The right field will have the same horizontal binning factor as the left field. Thus for each window, there are three possibilities for horizontal binning:
Each window is positioned horizontally by specifying the number of pixels after the reference column. This number is allowed to be negative by a small amount. DO NOT OVERLAP THE WINDOWS, since the software cannot cope with this.
The reference column is nominally the ``left'' edge of the chip, and is column 1 for all GEC CCDs (i.e.\ the first data column). For the RCA chip, there is currently an error of 8 columns, because the extension of the readout register is three pixels rather than eleven for the GEC chips. This will be corrected in a future version of the microcode by allowing the readout register overhang to be specified by a hardware command.) For now, the reference column for the RCA chip is column -7, where column 1 is again the first data column.
Both windows must start at the same row, and the vertical position is specified by the number of pixel lines after the reference line (which is always the first row of the chip, i.e. line 1).
The following tables show the definitions of the `parameters' used in window definition files
| Vertical Parameters | |
|---|---|
| CCD-LTW | Lines to window. (0 = nominal start of CCD chip) |
| CCD-NVF | Number of vertical fields. (1 , 2 or 3) |
| CCD-LPBM | Lines per bin in middle or only field |
| CCD-NBMF | Number of image (data) rows in middle or only field |
| CCD-LPBF | Lines per bin in the first field of two or three fields |
| CCD-NBFF | Number of image (data) rows in the first field of 2 or 3 |
| Left Window Horizontal Parameters | |
|---|---|
| CCD-PTLW | Pixels to left (first) window. (0 = nominal edge) |
| CCD-NFLW | Number of fields in left window. (1, 2 or 3) |
| CCD-BCLW | Number of bins in centre or only field of left window |
| CCD-PCLW | Pixels per bin in centre or only field of left window |
| CCD-BLLW | Number of bins in left field of left window |
| CCD-PLLW | Pixels per bin in left field of left window |
| CCD-BRLW | Number of bins in right field of left window |
| Right Window Horizontal Parameters | |
|---|---|
| CCD-PTRW | Pixels to right (second) window |
| CCD-NFRW | Number of fields in right window |
| CCD-BCRW | Number of bins in centre or only field of right window |
| CCD-PCRW | Pixels per bin in centre or only field of right window |
| CCD-BLRW | Number of bins in left field of right window |
| CCD-PLRW | Pixels per bin in left field of right window |
| CCD-BRRW | Number of bins in right field of right window |
The window should be defined in an ASCII file with extension .WINDOW. The default locations are the directories pointed to by the logical name WINDOWS_DIR (see above). The general layout of existing (successful) definition files should be followed. See the examples below, and note that the numeric fields of the .WINDOW files end in column 30.
CCD-WINS= 'FORS ' / WINDOW NAME CCD-LTW = -8 / LINES TO WINDOW CCD-NVF = 1 / NUMBER OF VERTICAL FIELDS CCD-NBFM= 584 / NUMBER OF BINS IN MIDDLE FIELD CCD-LPBM= 1 / LINES PER BIN IN MIDDLE FIELD CCD-PTLW= -1 / PIXELS TO LEFT WINDOW CCD-NFLW= 1 / NUMBER OF FIELDS IN LEFT WINDOW CCD-BCLW= 1 / NO. OF BINS IN C. FIELD OF L. WNDW CCD-PCLW= 1 / PIXELS PER BIN CENTER FIELD L. WNDW CCD-PTRW= 74 / PIXELS TO RIGHT WINDOW CCD-NFRW= 1 / NUMBER OF FIELDS IN RIGHT WINDOW CCD-BCRW= 256 / NO. OF BINS IN C. FIELD OF R. WNDW CCD-PCRW= 1 / PIXELS PER BIN C. FIELD R. WNDW END
The final data frame recorded on disk will contain 256 columns x 584 rows. Rows 1-8 sample the bias overscan region. The figure below shows the location of this window on the GEC chip. Note that windows for the GEC chip start at column PTLW or PTRW +1.
CCD-WINS= 'RCA_STAN ' / RCA CHIP - STANDARDS AREA CCD-LTW = 171 / LINES TO WINDOW CCD-NVF = 1 / NUMBER OF VERTICAL FIELDS CCD-NBFM= 170 / NUMBER OF BINS IN MIDDLE FIELD CCD-LPBM= 1 / LINES PER BIN IN MIDDLE FIELD CCD-PTLW= 92 / PIXELS TO LEFT WINDOW CCD-NFLW= 1 / NUMBER OF FIELDS IN LEFT WINDOW CCD-BCLW= 170 / NO. OF BINS IN C. FIELD OF L. WNDW CCD-PCLW= 1 / PIXELS PER BIN CENTER FIELD L. WNDW CCD-PTRW= 319 / PIXELS TO RIGHT WINDOW CCD-NFRW= 1 / NUMBER OF FIELDS IN RIGHT WINDOW CCD-BCRW= 30 / NO. OF BINS IN C. FIELD OF R. WNDW CCD-PCRW= 1 / PIXELS PER BIN C. FIELD R. WNDW END
This is a double window, used for observing standard stars when imaging with the RCA CCD. The left window covers 170 x 170 pixels near the centre of the chip, while the right window covers the bias overscan region. The final data frame will have 200 columns x 170 rows, with the data in columns 1-170. The starting column on the RCA chip is currently defined as PTLW or PTRW + 9.
CCD-WINS= 'GEC17-PAIR2 ' / WINDOW NAME LTW = -8 / LINES TO WINDOW NFL = 1 / NUMBER OF VERTICAL FIELDS NBFM = 584 / NUMBER OF BINS IN MIDDLE FIELD LPBM = 1 / LINES PER BIN IN MIDDLE FIELD PTLW = 160 / PIXELS TO LEFT WINDOW NFLW = 1 / NUMBER OF FIELDS IN LEFT WINDOW NBFCLW = 10 / NO. OF BINS IN C. FIELD OF L. WNDW PPBCLW = 2 / PIXELS PER BIN CENTER FIELD L. WNDW PTRW = 210 / PIXELS TO RIGHT WINDOW NFRW = 1 / NUMBER OF FIELDS IN RIGHT WINDOW NBFCRW = 10 / NO. OF BINS IN C. FIELD OF R. WNDW PPBCRW = 2 / PIXELS PER BIN C. FIELD R. WNDW END
This defines a pair of windows on the GEC chip, with the data double-binned in columns in each window. The final data frame will have 20 columns x 584 rows, where rows 9-584 have useful data and rows 1-8 sample the bias overscan region. Columns 1-10 have data from the left window and columns 11-20 data from the right window.
CCD-WINS= 'TEK1K_DIRECT' / Window name. CCD-LTW = 0 / CCD chip lines to window CCD-NVF = 1 / Number of vertical binning fields CCD-LPBM= 1 / No vertical binning CCD-NBFM= 1024 / Number of rows CCD-PTLW= 0 / CCD pixels to left window CCD-NFLW= 1 / No. horiz. binning fields in L.window CCD-PCLW= 1 / No horizontal binning in left window CCD-BCLW= 1028 / Number of columns in left window CCD-PTRW= 1028 / CCD pixels to right window CCD-NFRW= 1 / No. horiz. binning fields in R.window CCD-PCRW= 1 / No horizontal binning in right window CCD-BCRW= 22 / Number of columns in right window END
A full sized window (1028x1024) with a bias overscan (22x1024)
CCD-WINS= 'TEK1K_DIRECT_CEN' / Window name. CCD-LTW = 365 / CCD chip lines to window CCD-NVF = 1 / Number of vertical binning fields CCD-LPBM= 1 / No vertical binning CCD-NBFM= 300 / Number of rows CCD-PTLW= 365 / CCD pixels to left window CCD-NFLW= 1 / No. horiz. binning fields in L.window CCD-PCLW= 1 / No horizontal binning in left window CCD-BCLW= 300 / Number of columns in left window CCD-PTRW= 1028 / CCD pixels to right window CCD-NFRW= 1 / No. horiz. binning fields in R.window CCD-PCRW= 1 / No horizontal binning in right window CCD-BCRW= 22 / Number of columns in right window END
A 300x300 pixel window in the centre of the TEK CCD, with a 22x300 pixel bias overscan
CCD-WINS= 'TEK1K_CEN_100' / Window name. CCD-LTW = 450 / CCD chip lines to window CCD-NVF = 1 / Number of vertical binning fields CCD-LPBM= 1 / No vertical binning CCD-NBFM= 100 / Number of rows CCD-PTLW= 450 / CCD pixels to left window CCD-NFLW= 1 / No. horiz. binning fields in L.window CCD-PCLW= 1 / No horizontal binning in left window CCD-BCLW= 100 / Number of columns in left window CCD-PTRW= 1028 / CCD pixels to right window CCD-NFRW= 1 / No. horiz. binning fields in R.window CCD-PCRW= 1 / No horizontal binning in right window CCD-BCRW= 0 / Number of columns in right window END
A 100x100 pixel window in the centre of the TEK chip, with a 1x100 pixel overscan.
CCD-WINS= 'THOMSON_F1' / Window name. CCD-LTW = 0 / CCD chip lines to window CCD-NVF = 1 / Number of vertical binning fields CCD-LPBM= 1 / No vertical binning CCD-NBFM= 1024 / Number of rows CCD-PTLW= 0 / CCD pixels to left window CCD-NFLW= 1 / No. horiz. binning fields in L.window CCD-PCLW= 1 / No horizontal binning in left window CCD-BCLW= 1024 / Number of columns in left window CCD-PTRW= 1024 / CCD pixels to right window CCD-NFRW= 1 / No. horiz. binning fields in R.window CCD-PCRW= 1 / No horizontal binning in right window CCD-BCRW= 40 / Number of columns in right window END
A 1024x1024 pixel window (the ful chip) and a 40x1024 pixel overscan region
CCD-WINS= 'THOMSON_F1_CENTRE' / Window name. CCD-LTW = 363 / CCD chip lines to window CCD-NVF = 1 / Number of vertical binning fields CCD-LPBM= 1 / No vertical binning CCD-NBFM= 300 / Number of rows CCD-PTLW= 363 / CCD pixels to left window CCD-NFLW= 1 / No. horiz. binning fields in L.window CCD-PCLW= 1 / No horizontal binning in left window CCD-BCLW= 300 / Number of columns in left window CCD-PTRW= 1024 / CCD pixels to right window CCD-NFRW= 1 / No. horiz. binning fields in R.window CCD-PCRW= 1 / No horizontal binning in right window CCD-BCRW= 40 / Number of columns in right window END
A 300x300 pixel window centred in the centre of the chip, with a 40x300 pixel overscan region.
CCD-WINS= 'THOMSON_BIN2' / Window name. CCD-LTW = 1 / CCD chip lines to window CCD-NVF = 1 / Number of vertical binning fields CCD-LPBM= 2 / Vertical binning factor CCD-NBFM= 512 / Number of (binned) rows CCD-PTLW= 7 / CCD pixels to left window CCD-NFLW= 1 / No. horiz. binning fields in L.window CCD-PCLW= 2 / Horizontal binning factor - left windo CCD-BCLW= 1 / Number of binned columns in left windo CCD-PTRW= 9 / CCD pixels to right window CCD-NFRW= 1 / No. horiz. binning fields in R.window CCD-PCRW= 2 / Horizontal binning factor - right wind CCD-BCRW= 511 / Number of binned columns in right wind END
A 512x512 bin window (binned in X and Y - 2 pixels per bin), offset by 8 pixels in the X direction.
CCD-WINS= 'THOMSON_F1_TEST' / Window name. CCD-LTW = 0 / CCD chip lines to window CCD-NVF = 1 / Number of vertical binning fields CCD-LPBM= 1 / No vertical binning CCD-NBFM= 1024 / Number of rows CCD-PTLW= 500 / CCD pixels to left window CCD-NFLW= 1 / No. horiz. binning fields in L.window CCD-PCLW= 1 / No horizontal binning in left window CCD-BCLW= 10 / Number of columns in left window CCD-PTRW= 510 / CCD pixels to right window CCD-NFRW= 1 / No. horiz. binning fields in R.window CCD-PCRW= 1 / No horizontal binning in right window CCD-BCRW= 1 / Number of columns in right window END
This 10 x 1024 pixel window is for making short test observations with the Thomson CCD. Its usual shape prevents the `fast readout' mode from saturating the readout register (by binning many otherwise unsaturated pixels into the readout register). Use it to test levels of flat field exposures.
Time Series Mode is a special CCD readout mode which uses charge sguffling techniques to continuously observe with and read from an AAO CCD, to create a data cube with a time axis. It is mostly used for spectroscopy. A discussion of its use on the RGO can be found in the RGO Manual Section 6.3.
Introduction
The Telescope
& Optics
The
Detectors
The Imaging
Cameras
An Imaging
Cookbook
The Data
you Take Away
Exposure
times
OFFSET_RUN
files
CCD
Windows
Data
Catalogs
On-line
Reduction
Filters
Flat-fields
Blank
Fields
Orientation
Shutters
This Page maintained by : Chris Tinney (cgt@aaoepp.aao.gov.au)
This Page last updated: 8 Mar 1996, by Chris Tinney
