1. CCD Parameters
2. CCD Commands
3. CCD Windows
4. File formats
5. CCD Dewars
The Tektronix CCD has a physical size of 24.6 x 24.6 mm, with 1024 x 1024 pixels. The pixel size is 24 microns. The detector is operated at either 170 K (normal) or at 200 K. For UCLES and UHRF the detector is always used at 170K due to the much lower dark current at 170 K than at 200 K.
| Mode | Readout Noise (e- rms) |
Gain (e-/ADU) |
Saturation Level (e-/pix) |
Readout Time full chip binned x 2 |
|---|---|---|---|---|
| XTRASLOW | 2.3 | 0.34 | 22,000 | 394 |
| SLOW | 3.6 | 1.36 | 88,000 | 120 |
| NORMAL | 4.8 | 2.74 | 180,000 | 75 |
| FAST | 7.2 | 5.5 | 370,000 | 33 |
| NONASTRO | 11.0 | 11 | 385,000 | 25 |
Dark current : @ 170K approx 0.55 e-/pix/2000s
Dark Current : @ 200K approx 0.10 e-/pix/1s
Saturation level: 65K ADU
Typical cosmic ray event number : 730 per 2000s
| Mode | Readout Noise (e- rms) |
Gain (e-/ADU) |
Saturation Level (e-/pix) |
Readout Time full unbinned chip |
|---|---|---|---|---|
| XTRASLOW | 1.3 | 0.093 | 9,000 | 940 |
| SLOW | 1.45 | 0.366 | 23,000 | 300 |
| NORMAL | 2.00 | 1.11 | 70,000 | 160 |
| FAST | 2.9 | 2.3 | 145,000 | 95 |
| NONASTRO | 5.2 | 4.6 | 100,000 | 60 |
Dark current : @ 170K approx 0.30 e-/pixel/4000s
| Mode | Readout Noise (e- rms) |
Gain (e-/ADU) |
Saturation Level (e-/pix) |
Readout Time full unbinned chip |
|---|---|---|---|---|
| XTRASLOW | 1.3 | 0.088 | 6,000 | 924 |
| SLOW | 1.6 | 0.36 | 23,000 | 285 |
| NORMAL | 2.0 | 1.1 | 62,000 | 143 |
| FAST | 2.9 | 2.2 | 148,000 | 108 |
| NONASTRO | 5.2 | 4.7 | 150,000 | 58 |
Dark current : @ 160K < 0.8 e-/pixel/4000s after allowing time to settle.
Choosing between the TEK and MITLLs:
Both the TEK and MITLL2 device may be used with UCLES and UHRF (Since the MITLL3 cannot be binned on-chip, it is not suitable for use with UHRF). The MITLL2/3 provides smaller pixels (15um vs 24um) and a larger wavelength coverage in the spectral direction. Resoving powers approaching 80000 are possible with the MITLL2/3, but only with a sub-arcsecond slit. For UHRF, resolutions of 900,000 have been obtained with the MITLL2. The main reason for preferring the TEK over the MITLL2/3 devices is its superior QE for wavelengths below 5000 Angstroms. The MITLL3 has a higher quantum efficiency than the MITLL2 at all wavelengths above 4200 Angstroms, but MITLL3 also has a substantially higher number of cosmic rays.
It may be necessary to type:
vax: VERSION date
Then start up CCD with
vax: CCDL_VAC (or vax: CCDU_VAC)
vax: CCD_1 (or vax: CCD_2 )
(The controller and CCD in use are given on the control room whiteboard).
CCD Commands
| Command | Action | |
|---|---|---|
| FITSINFO | gives the current inputs for the OBSERVER and INSTRUMENT commands | |
| OBSERVER | Set the observer name(s) | |
| INSTRUMENT | Set the instrument number, 21 for UCLES + 70 cm camera | |
| DATA USHORT | Use a compressed data format. This is essential for unbinned MITLL files | |
| DATA FLOAT | Use the standard, uncompressed data format | |
| COLOUR X | Se the display colour X = GRAY, GRTJ, others | |
| SPEED Y | Se the readout speed. Y = XTRASLOW, SLOW, NORMAL, FAST. NONASTRO | |
| WINDOW Z | Set the CCD window. See the list of windows below. | |
| DUMMY N | Dummy exposure of n seconds, written to disk$data: | |
| GLANCE N | Glance exposure of n seconds, not written to disk | |
| RUN N | Run exposure of n seconds, written to disk$inst: | |
| REPEAT M | Repeat exposures, m = inclusive number of repeats | |
| REPEAT | open ended repeat | |
| SINGLE | Turn off repeat | |
| BIAS | Take bias frame (0s exposure) | |
| OBJECT name | Set the object name | |
| DARK N | Take exposure with shutter closed (dark frame) | |
| ARC | Start exposure and log this as an Arc frame (arc lamp must be turned on separately). | |
| FLAT | Start exposure and log this as a Flatfield (quartz lamp must be turned on separately). | |
| HOLD | Pause the exposure | |
| TIME N | Change time during exposure | |
| EXIT | exit from CCDs | |
| NEXT 1 | sets next frame number to 1 | |
| RECOVER XMEM | Attempt to recover data before lost from XMEM | |
| RECOVER CCD | Attempt to recover data before lost from CCD | |
| SPAWN | gives the dcl prompt | |
| USE_INST1 | change from disk$inst to disk$inst1 | |
| LO | Logs out of dcl | |
| RESET SOFT | rest the XMEM and controllers (must be reset after use_disk) |
| Detector | Window file | Window size | Notes |
|---|---|---|---|
| TEK | TEK1K_SETUP | 121x1024 | Used for setting up |
| TEK | TEK1K_X2 | 525 x 1024 | Binned x 2 in x Standard UCLES window |
| TEK | TEK1K_DIRECT_CEN | 322 x 300 | Central window - no binning |
| TEK | TEKTRONIX_EXACT | 1028 x 1024 | exact window + four overscans |
| MITLL2/3 | MITLL_FULL | 4096 x 2048 | Full window, no binning |
| MITLL2/3 | MITLL_CENTRE | 1000 x 1000 | Centre window, no binning |
| MITLL2 | MITLL_FULL_B1X4 | 4096 x 530 | full window, binned x 4 in y |
| MITLL2 | MITLL_PLANET_BX2 | 2088 x 2496 | "Planet Search" window, binned x 2 in x |
Window files for the Tek CCD are in VAX directories with names similar to:
disk$user:[sysdisk1.adamlocalwindow.q0_1a]
MITLL2/3 window files are in the VAX directory with names similar to:
disk$user:[sysdisk1.adamlocalwindow.ro_0]
To create a new CCD window file, copy an example file to observer account. Then edit this to create a new window file. To use the new window just give full path in CCD windows command - or copy file over to the permanent directory area. This has to be done by someone with appropriate file-writing permission.
To plot a CCD window, login as username=NIGHT.
vax: XON device name
vax: PGWINDOW , this should plot the window, or use
vax: WINDOWS
Dummy files and run files are written in sdf format to the VAX disks
DISK$DATA:[CCD_n.date]
DISK$INST:[CCD_n.date]
DISK$INST1:[CCD_n.date]
DISK$INST2:[CCD_n.date]
These can be accessed from unix workstations as i.e.
/vaxdata/ccd_n/date
/vaxinst/ccd_n/date
Data files can also be written in FITS and IRAF formats using the unix-server facility. To use this, make sure the the unix server on aatssf is running : If not then from obsred or other unix account type
unix: xhost aatssf
Files in FITS and IRAF formats are written to:
/data/ssf/1/obsred/fits/ccd_n/date
/data/ssf/1/obsred/iraf/ccd_n/date
To see space left on INST, INST1 and INST2:
vax: SHOW DEV D
To change from disk$inst to disk$inst1 use the ccd commands:
ccd: SPAWN
vax: USE_INST1
vax: LO
ccd: RESET SOFT