New FITS keywords in the primary header
General keywords in the primary header
| Keyword name | Value | Description |
|---|
| RADECSYS | FK5 | Celestial
coordinate system |
| EQUINOX | 2000. | Equinox of celestial
coordinate system |
| OBSGEO-X | 5327395.9638 | Cartesian
Coordinate X of telescope |
| OBSGEO-Y | -1719170.4876 | Cartesian
Coordinate Y of telescope |
| OBSGEO-Z | 3051490.766 | Cartesian
Coordinate Z of telescope |
| ORIGIN | NOTSA | Nordic Optical
Telescope Scientific Association |
| CREATOR | NOT2MEF V1.4.4 | Version of
FITS writing software |
| OBS_MODE | Imaging | Type of data (Imaging/Spectroscopy) |
| QCRDATE | 2004-11-24 | Instrument rotation centre reference date |
The keywords OBSGEO-X, OBSGEO-Y, and OBSGEO-Y are the geocentric
Cartesian triple incarnation of the traditional position on
earth expressed in longitude, latitude, and altitude. These values
were calculated based on GPS data for the location of the NOT.
Timing keywords in the primary header
For ALFOSC, STANCAM, MOSCA, FIES the start and midpoint of the actual
exposure are recorded in ISO8601 format. For NOTCAM these keywords
are not recorded in the primary header, but in the headers of the data
extensions, since the different extensions have different start times,
midpoints and exposure times.
| Keyword name | Value | Description |
|---|
| DATE-OBS | 2003-09-26T02:25:56.0 | Start of exposure |
| DATE-AVG | 2003-09-26T02:26:26.0 | Midpoint of exposure |
Special NOTCAM headers
To facilitate the amplifier-dependent data reduction for NOTCAM several
keywords have been added to the primary header. Together with a
special translation file these can be used to
create multiextension format from images with multiple amplifier readouts
recorded as sections of a single image.
New FITS keywords in data extensions
Mandatory keywords in data extensions
The new NOT data extensions have the following mandatory keywords with
mandatory values:
| Keyword name | Value | Description |
|---|
| XTENSION | IMAGE | Image data
extension |
| PCOUNT | 0 | Required keyword in
data extension |
| GCOUNT | 1 | Required keyword in
data extension |
Additional keywords describing the data extensions
These optional keywords describe the data extension itself. Values listed are examples.
| Keyword name | Value | Description |
|---|
| EXTNAME | im1 | Extension name |
| IMAGEID | 1 | ID of data extension |
Primary WCS for imaging data
| Keyword name | Value | Description |
|---|
| CTYPE1 | RA---TAN | Name of coordinate (RA, gnomonic projection) |
| CTYPE2 | DEC--TAN | Name of coordinate (Dec, Gnomonic projection) |
| CRVAL1 | | RA at reference point |
| CRVAL2 | | Dec at reference point |
| CUNIT1 | deg | Unit of 1st axis |
| CUNIT2 | deg | Unit of 2nd axis |
| CRPIX1 | | Reference pixel on 1st axis |
| CRPIX2 | | Reference pixel on 2nd axis |
| CD1_1 | | Element of transformation matrix for primary WCS |
| CD1_2 | | Element of transformation matrix for primary WCS |
| CD2_1 | | Element of transformation matrix for primary WCS |
| CD2_2 | | Element of transformation matrix for primary WCS |
Linear pixel WCS for spectroscopic data
| Keyword name | Value | Description |
|---|
| CTYPE1 | X | Coordinate name |
| CTYPE2 | Y | Coordinate name |
| CRVAL1 | | X at reference point |
| CRVAL2 | | Y at reference point |
| CUNIT1 | pixel | Unit of 1st axis |
| CUNIT2 | pixel | Unit of 2nd axis |
| CRPIX1 | | Reference pixel on 1st axis |
| CRPIX2 | | Reference pixel on 2nd axis |
| CDELT1 | | Increment on 1st axis |
| CDELT2 | | Increment on 2nd axis |
Detector characteristics
| Keyword name | Value | Description |
|---|
| QCDDATE | | Detector characteristics reference date |
| RDNOISE | | Read-out noise [e-] |
| GAIN | | [e-/ADU] |
| DARK | | [e-/hr/pix] |
Extra IRAF-style keywords
| Keyword name | Value | Description |
|---|
| CCDNAME | | Name of detector, used by IRAF
ccdproc, mscred |
| CCDSUM | 1 1 | On chip binning factors, used by
IRAF ccdproc, mscred |
| DATASEC | | Location of data pixels |
| TRIMSEC | | Section of useful data |
| BIASSEC | | Location of bias pixels |
Extra IRAF-style keywords for mosaic data
| Keyword name | Value | Description |
|---|
| DETSEC | | Location in final mosaic |
| CCDSEC | | Location on CCD |