INT-DAS-2

FITS Headers for
INT Observations

Guy Rixon, Mike Irwin, Peter Bunclark & James Lewis

Issue 3.3; 1997-09-12

 

 

 

 


Royal Greenwich Observatory,
Madingley Road,
Cambridge CB3 0HJ

Telephone (01223) 374000
Fax (01223) 374700
Internet gtr@mail.ast.cam.ac.uk

1 Introduction

1.1 Purpose of this document

This is the Interface-Control Document for the passing of FITS headers from the various INT observing systems to the associated data-export systems and thence to the observers. As such, the document defines the set of descriptors that a `consumer' of the data may expect to find in each FITS file. Once offically issued, this document is an authoritative specification. It is appropriate for authors of observing systems to claim conformance to a specific issue of this document.

1.2 Scope of the interface

The data-sets defined are those written to D-tapes and C-tapes and those presented to the observers as disk-FITS files. No mention is made of the way in which the data get into those files and any intermediate files are not covered by this specification. It may be assumed that FITS files are not accessible to the observers, or to software other than observing and logging systems until the files are complete.

1.3 Division of headers into packets

For convenience of description, each FITS header may be built from separate packets, each packet containing one or more descriptors. Once assembled, the boundaries between packets must be invisible and it must be possible for external software to process the header without knowing about the packets. The packets should appear in the order given, and within each packet, the descriptors must appear in the order specified below.

The names of the packets form part of the interface between the DAsS and other sub-systems. Tasks that write packetsmust produce them with the names given below.

After the last descriptor of the last packet, shall be present a descriptor with the HISTORY keyword marking the end of the part of the header that was written during observation. Any subsequent descriptors are then clearly the result of data reduction.

These are the lists of packets that need to be collected:

WFC: observation wcs telescope autoguider wfc exposure ccd ccdproc

IDS: observation wcs telescope autoguider cagb ids exposure ccd ccdproc

2 Image-size packet

The descriptors listed in this section shall be present at the start of every FITS-file written at the INT. They indicate how to read the image from the file.

 

Keyword

Constant value

Variable type

Notes

SIMPLE

T

 

All files are simple FITS.

BITPIX

16

 

All files contain 16-bit images.

NAXIS

 

integer

Number of axes in the image.

NAXISn

 

integer

Number of pixels in nth axis. n descriptors as appropriate.

BSCALE

1.0

 

Image data have not been rescaled.

BZERO

32768.0

 

Image data have the offset required to fit 16-bit unsigned data into a 16-bit signed range.

 

The use of these descriptors is strictly defined in the NASA FITS standard, NOST 100-1.0. The order of SIMPLE, BITPIX, NAXIS and NAXISn is part of the standard. The BLOCKED keyword is not used.

This packet has no formal name. The data are provided directly by the DAsS and the packet is not collected in thesame way as other packets.

3 Observation packet

This packet contains data that cannot be derived from any single sub-system of the observing system.

 

Keyword

Constant value

Variable type

Notes

RUN

 

integer

The run number.

SYSVER

 

character

Version number of the observing system plus list of software patches.

ORIGIN

'ING La Palma'

 

As used at the WHT.

OBSERVAT

'LAPALMA'

 

Used by IRAF

OBSERVER

 

character

Typically, this contains the observer's initials.

PROPOSAL

 

character

This is the code for the PATT/CAT proposal.

DATEARCH

 

character

Date of observation in format yyyy/mm/dd

OBJECT

 

character

If the observer has entered a title for the observation, it appears here. Otherwise, the name of the current target should be used, or the words ARC, BIAS, FLAT, SKY etc. as appropriate.

OBSTYPE

 

character

This should be one of TARGET, BIAS, FLAT, ARC, SKY, FLAT, DARK, MAP, FOCUS.

IMAGETYPE

 

character

Same as OBSTYPE: needed by IRAF.

 

All these descriptors can be built at the start of the observation.

ORIGIN is written to match WHT headers. OBSERVAT, with the precise value shown above, is used by some IRAF programs to select site-specific data.

This packet is named observation.

4 World-coordinate-system packet

This packet defines the registration of the image to celestial coordinates. The form of the packet should be reviewed as the WCS conventions for FITS evolve.

 

Keyword

Constant value

Variable type

Notes

CTYPE1

 

character

Type world coordinates mapped to x axis. Usually 'RA', or 'DEC'.

CRPIX1

 

real

Reference pixel for world coordinates on x axis.

CRVAL1

 

real

World-coordinate value at reference pixel, x axis.

CDELT1

 

real

Interval in world coordinates between pixel centres, x axis.

CROTA1

 

real

Rotation of x axis from the world-coordinate type stated in CTYPE1.

CTYPE2

 

character

Type of world coordinates mapped to y axis. Usually 'RA', or 'DEC'.

CRPIX2

 

real

Reference pixel for world coordinates on y axis.

CRVAL2

 

real

World-coordinate value at reference pixel, y axis.

CDELT1

 

real

Interval in world coordinates between pixel centres, y axis.

CROTA1

 

real

Rotation of y axis from the world-coordinate type stated in CTYPE1.

 

The axis-type keywords can be omitted for axes that are not mapped to position on the sky. Where world coordinates are RA or dec., CDELTn and CVALn are given in degrees. CROTAn is always in degrees.

All these descriptors can be built at the start of the observation.

This packet is named wcs.

5 Telescope packet

 

Keyword

Constant value

Variable type

Notes

TELESCOPE

INT

 

Name of telescope.

LATITUDE

'28:45:38.5'

 

Latitude of telescope.

LONGITUD

'17:52:39.5'

 

Longitude of telescope.

SLATEL

'LPO2.5'

 

The name for the telescope as understood by the library subroutine sla_OBS().

CAT-NAME

 

character

The name of the target as stored in the target list. May be different from the name stored under OBJECT.

CAT-RA

 

character

Taken from the target list. In the format hh:mm:ss.ss.

CAT-DEC

 

character

Taken from the target list. In the format sdd:mm:ss.s.

CAT-EQUI

 

character

Equinox of the target's coordinates, taken from the target list. In the format Jnnnn.n, Bnnnn.n or A, where nnnn.n is in years AD.

CAT-EPOC

 

real

Epoch of the target's coordinates, taken from the target list. In years AD as a decimal fraction.

PM-RA

 

real

Proper motion in R.A. In seconds of time per year.

PM-DEC

 

real

Proper motion in dec. In seconds of arc per year.

PARALLAX

 

real

Half-annual parallax in seconds of arc.

RADVEL

 

real

Heliocentric radial velocity of the target in km?s-1.

RATRACK

 

real

Differential-tracking rate in arcsec/second in r.a.

DECTRACK

 

real

Differential-tracking rate in arcsec/second in dec.

RA

 

character

R.A. that the telescope is tracking. In the format hh:mm:ss.ss.

DEC

 

character

Dec. that the telescope is tracking. In the format sdd:mm:ss.s.

EQUINOX

 

character

Equinox of the coordinates in RA, DEC. Ideally, these coordinates should be given to the same equinox as CAT-RA and CAT-DEC. Same format as CAT-EQUI.

STSTART

 

character

Local sidereal time at the start of the observation.

ST

 

character

Same as STSTART

AZIMUTH

 

real

Mean azimuth of telescope during observation. In degrees.

ZD

 

real

Mean zenith distance during observation. In degrees.

AIRMASS

 

real

Mean airmass during observation.

XAPOFF

 

real

Offset from nominal pointing in `x'. In seconds of arc.

YAPOFF

 

real

Offset from nominal pointing in `y'. In seconds of arc.

ROTTRACK

T

 

Always set to true, since an equatorial telescope does not need a tracking rotator.

ROTSKYPA

 

real

Mean position of rotator during observation. In degrees.

PARANGLE

 

real

Parallactic angle. In degrees.

VIGNETTE

 

boolean

True if the mirror petals or the dome vignette the telescope's beam.

DOMEAZ

 

real

Mean azimuth of dome during observation. In degrees.

TELFOCUS

 

real

Position of telescope's focus drive. In metres. The sense of focus movement may vary between foci.

TEMPTUBE

 

real

Temperature of telescope tube in degrees Celsius.

 

The quantities defined as `average...during observation' are the mean of samples at regular intervals, starting with the clearing of the CCD for each exposure and ending at the start of CCD readout. It is assumed that the sampling rate is high enough to track non-linear variations in these quantities.

The definitions of CAT-EQUI and EQUINOX conflicts, by the presence of the prefix-letter for the calender system, with NASA's standard for the use of FITS. It may be better to state the calender system under a separate keyword.

This packet is named telescope.

6 Autoguider packet

 

Keyword

Constant value

Variable type

Notes

AUTACQT

 

real

Integration time (in seconds) for acquisition.

AUTGUIT

 

real

Integration time (in seconds) for guiding.

AUTWINDO

 

integer

Number of autoguider window.

AUTMODE

 

character

Name of autoguider mode.

AUTXSEE

 

real

Mean FWHM (arcsec) of guide star, x-axis.

AUTYSEE

 

real

Mean FWHM (arcsec) of guide star, y-axis.

AUTXSRMS

 

real

RMS on FWHM (arcsec) of guide star, x-axis.

AUTYSRMS

 

real

RMS on FWHM (arcsec) of guide star, y-axis.

AUTMAGNI

 

real

Mean magnitude of guide star.

AUTTRANS

 

real

RMS variation of magnitude of guide star.

AUTMAGOF

 

real

Magnitude zero-point.

AUTSTATN

 

integer

Number of readings used for statistical calculations.

AUTOMODE

 

character

Mode of autoguiding.

AUTOX

 

real

Guiding position on autoguider, x-axis.

AUTOY

 

real

Guiding position on autoguider, y-axis.

 

The mean and RMS value above are calculated from the readings made between the start and end of each exposure,

Some descriptors in this packet cannot be collected until the end of the exposure.

This packet is named autoguider.

7 Exposure packet

This packet records the timing of the exposure. Typically, these data come from the CCD controller, but some observations may have other sources.

 

Keyword

Constant value

Variable type

Notes

DATE-OBS

 

character

Date of observation in the FITS-approved format.

UTSTART

 

character

UTC of start of observation. In the format hh:mm:ss.s.

ELAPSED

 

real

Length of exposure, including pauses, from end of clearing to start of readout. In seconds.

DARKTIME

 

real

Same as ELAPSED.

EXPOSED

 

real

Length of exposure, excluding pauses, from the first opening of the shutter to its final closing. In seconds.

EXPTIME

 

real

Same as EXPOSED.

 

This packet cannot be completed until the end of the observation.

DATE-OBS is the UT date and changes at 0000hrs UTC. The FITS standard specifies two exact formats for this datum: observation dates before 1st January 1998 shall be in the format dd/mm/yy; later dates shall be in the format ccyy-mm-dd. DATE-OBS and UTSTART must be derived from the same time-stamp. It is an error for UTSTART and DATE-OBS to refer to instants on opposite side of the date-change at midnight.

This packet is named exposure.

8 CCD packet

This packets describes the CCD and how it was read out. Details of how the pixel data were finally stored on disk are in the CCDPROC packet, below.

 

Keyword

Constant value

Variable type

Notes

BUNIT

'ADU'

 

Unit of the array of image-data.

GAIN

 

real

Electrons per ADU.

READNOISE

 

real

Readout noise per pixel. In electrons.

CCDSPEED

 

character

Readout speed of CCD.

CCDNCHIP

 

integer

Number of CCDs in this head.

CCDCHIP

 

integer

Number of this CCD within its head.

CCDTYPE

 

character

Name of the this CCD chip (technically, the name of the cryostat such as EEV7).

CCDXSIZE

 

integer

Size in pixels of digitized CCD frame; x-axis.

CCDYSIZE

 

integer

Size in pixels of digitized CCD frame; y-axis.

CCDXIMSI

 

integer

Size in pixels of useful imaging-area; x-axis.

CCDYIMSI

 

integer

Size in pixels of useful imaging-area; y-axis.

CCDXIMST

 

integer

Start pixel of useful imaging-area; x-axis.

CCDYIMST

 

integer

Start pixel of useful imaging-area; y-axis.

CCDWMODE

 

boolean

True if windowing is in force.

CCDWXO1

 

integer

Offset of window 1, x-axis.

CCDWYO1

 

integer

Offset of window 1, y-axis.

CCDWXS1

 

integer

Size in pixels of window 1, x-axis.

CCDWYS1

 

integer

Size in pixels of window 1, y-axis.

CCDWXO2

 

integer

Offset of window 2, x-axis.

CCDWYO2

 

integer

Offset of window 2, y-axis.

CCDWXS2

 

integer

Size in pixels of window 2, x-axis.

CCDWYS2

 

integer

Size in pixels of window 2, y-axis.

CCDWXO3

 

integer

Offset of window 3, x-axis.

CCDWYO3

 

integer

Offset of window 3, y-axis.

CCDWXS3

 

integer

Size in pixels of window 3, x-axis.

CCDWYS3

 

integer

Size in pixels of window 3, y-axis.

CCDWXO4

 

integer

Offset of window 4, x-axis.

CCDWYO4

 

integer

Offset of window 4, y-axis.

CCDWXS4

 

integer

Size in pixels of window 4, x-axis.

CCDWYS4

 

integer

Size in pixels of window 4, y-axis.

CCDXPIXE

 

real

Size in microns of pixels, x-axis, before binning.

CCDYPIXE

 

real

Size in microns of pixels, y-axis, before binning.

CCDXBIN

 

integer

Binning factor, x-axis.

CCDYBIN

 

integer

Binning factor, y-axis.

CCDSTEMP

 

integer

Required temperature of CCD, in kelvin.

CCDATEMP

 

integer

Actual temperature of CCD in kelvin.

PREFLASH

 

real

Length of preflash in seconds.

 

When considering position of windows and imageing-areas on the CCD, the following point should be noted.

z For any CCD, there exists a notional full-frame which is the set of pixels read out when there are no readout windows and the binning factors are both set to one. This full frame typically has more pixels than the physical CCD because it includes bias regions produced as overscan in the preamplifier. Binning and windowing create an actual CCD frame which can be no larger than the full frame, but may, because of overscan, be larger than the physical CCD.

z The descriptors CCDWxxn, which define the readout windows used, refer to regions of the full frame. If the actual frame is both windows and binned, the region read out for each window will be smaller than that described by CCDWxSn. The data-acquisition system arranges the windows to form an actual frame that is the smallest possible rectangle and hence CCDWxxn do not indicate where the windows are in the actual image.

z The descriptors CCDSEC, TRIMSEC, BIASSEC and WINSECn (ccdproc packet, below) refer to regions of the actual frame. They all have the format '[x1:x2,y1:y2]', where x1, x2, y1, y2 are the outermost rows and columns of the region.

z CCDSEC and TRIMSEC describe the region containing all the illuminated pixels. Pixels outside this region are blank or bias level. When multiple windows are used, the `illuminated' region may contain unilluminated pixels in the corners.

z BIASSEC describes the region from which the bias level should be measured.

z WINSECn describe the region containing readout window n.

z In descriptors CCDWxxx, the window start-pixels are expressed as offsets from the edge of the actual frame. A window with CCDWXOx set to zero includes the leftmost column of the frame. A window with CCDWYOx set to zero includes the bottom row of the frame. However, CCDSEC, TRIMSEC, BIASSEC and WINSECn count the first pixel in the frame as (1,1).

This packet can be completed at the start of the observation.

This packet is named ccd.

9 CCDPROC packet

This packet defines how the CCD data are arranged in the FITS file. The name of hte packet reflects the influence of IRAF in defining the descriptors.

 

Keyword

Constant value

Variable type

Notes

TRIMSEC

 

character

Region of actual CCD frame containing the image; in `section' format (see below).

CCDSEC

 

character

Same data as TRIMSEC.

BIASSEC

 

character

Region of actual CCD-frame containing the bias level; in `section' format (see below).

WINSECn

 

character

Region of actual CCD-frame containing data from readout window n, n = 1..4. In `section' format (see below).

READAXIS

 

character

The direction of readout w.r.t the axes of the image: `COLUMN' or `LINE'.

 

When considering position of windows and imageing-areas on the CCD, the following point should be noted.

z For any CCD, there exists a notional full-frame which is the set of pixels read out when there are no readout windows and the binning factors are both set to one. This full frame typically has more pixels than the physical CCD because it includes bias regions produced as overscan in the preamplifier. Binning and windowing create an actual CCD frame which can be no larger than the full frame, but may, because of overscan, be larger than the physical CCD.

z The descriptors CCDWxxn (ccd packet, above) which define the readout windows used, refer to regions of the full frame. If the actual frame is both windows and binned, the region read out for each window will be smaller than that described by CCDWxSn. The data-acquisition system arranges the windows to form an actual frame that is the smallest possible rectangle and hence CCDWxxn do not indicate where the windows are in the actual image.

z The descriptors CCDSEC, TRIMSEC, BIASSEC and WINSECn refer to regions of the actual frame. They all have the format '[x1:x2,y1:y2]', where x1, x2, y1, y2 are the outermost rows and columns of the region.

z CCDSEC and TRIMSEC describe the region containing all the illuminated pixels. Pixels outside this region are blank or bias level. When multiple windows are used, the `illuminated' region may contain unilluminated pixels in the corners.

z BIASSEC describes the region from which the bias level should be measured.

z WINSECn describe the region containing readout window n.

z In descriptors CCDWxxx, the window start-pixels are expressed as offsets from the edge of the actual frame. A window with CCDWXOx set to zero includes the leftmost column of the frame. A window with CCDWYOx set to zero includes the bottom row of the frame. However, CCDSEC, TRIMSEC, BIASSEC and WINSECn count the first pixel in the frame as (1,1).

This packet can be completed at the start of the observation.

This packet is named ccdproc.

10 Wide-field-camera packet

 

Keyword

Constant value

Variable type

Notes

INSTRUME

WFC

 

Name of instrument.

WFCFNAME

 

character

Type of filter e.g. Bkp

WFCFPOS

 

integer

Filter position (1..6).

WFCFID

 

character

Identifier for individual filter.

SECPPIX

0.37

 

Image scale in arcseconds per pixel.

 

These descriptors can be built at the start of the exposure.

The identifier for the filter is assumed to be some kind of serial number or code that uniquely identifies a particular item. Thus, there may be two filters available for which WFCNAME is Bkp but the have different values of WFCID. It is hoped that the unique identifiers can be extened to cover all filters used at ING.

This packet is named wfc.

11 Meteorological packet

At present, meteorological data are not available. Were they available, they would be compiled into this packet:

 

Keyword

Constant value

Variable type

Notes

TEMPOUT

 

real

Temperature outside the dome, in degrees C.

TEMPDOME

 

real

Temperature inside the dome in degrees C.

TEMPMIRR

 

real

Temperature of the primary mirror in degrees C.

TEMPTUBE

 

real

Temperature of the telescope tube in degrees C.

DIMM

 

real

Seeing measured on the Differential Image Motion Monitor; in seconds of arc.

WSPEED

 

real

Wind speed in km?h-1

WDIRECT

 

real

Wind direction in degrees east of north.

HUMIDITY

 

real

Relative humidity as a percentage.

PRESSURE

 

real

Atmospheric pressure in mbar.

DUSTDENS

 

real

Atmospheric extinction in magnitudes.

SKYBRGHT

 

real

Sky brightness in magnitudes per square arcsecond.

METMOLD

 

real

Time in seconds since measurements were obtained from the met. system.

METTOLD

 

real

Time in seconds since measurements were obtained from the TCS

METDOLD

 

character

Time in seconds since measurements were obtained from the DIMM.

METCOLD

 

character

Time in seconds since measurements were obtained from the meridian telescope.

 

Meteorological data comes from the central meteorological system, from the TCS (certain temperature readings), from the DIMM tower and from the Carlesberg meridan-telescope. Some of these links may be difficult to maintain during observing, and it is expected that data may be updated manually, probably a few times per night, in files that are always accessible to the observing system. The descriptors METxOLD indicate how long ago these files were last updated.

This packet is named meteorology.

12 IDS packet

This packet covers both IDS and FOS-1. All the descriptors are collected for each instrument even though a few are inapplicable to each.

 

Keyword

Constant value

Data type

Meaning

INSTRUME

IDS

 

Name of instrument.

SLITWID

 

real

Slit width in metres.

PSLITWID

 

real

Slit-width projected on detector in metres.

PAOFFSET

0.0

 

Slit PA telescope's sky PA in degrees.

SLTSKYPA

 

real

Position angle of slit on sky in degrees.

DEKKERID

 

character

Dekker-slide name.

DEKPOS

 

char

Name of Dekker-slide position.

BSCFILT

 

character

Name of colour filter in the beam below the slit.

BSNDFILT

 

character

Name of ND filter in the beam below the slit.

COLLNAME

 

character

Name of collimator.

COLLFOC

 

int

Collimator focus in encoder units.

HARTMANR

 

character

State of right Hartman-shutter: `OPEN' or `SHUT'.

HARTMANL

 

character

State of left Hartman-shutter: `OPEN' or `SHUT'.

CROSDISP

 

character

State of cross disperser: `IN' or `OUT'.

CLINESMM

 

int

Ruling density of cross disperser in lines per milimetre.

CDBLAZE

 

real

Blaze of cross disperser in Ângstroms.

CAMERA

 

character

Name of spectrograph camera: `235' or `500'.

GRATNAME

 

character

Name of grating.

GLINESMM

 

int

Ruling density of grating in lines per millimetre.

GRATBLAZE

 

real

Blaze of grating nm.

GRATANGL

 

real

Angle of grating in degrees.

GRATSHUT

 

character

State of grating shutter: `OPEN' or `SHUT'.

CENWAVE

 

real

Central wavelength of spectral image in nm.

DISPERSI

 

real

Spectra dispersion in nm of wavelength per mm of length projected on the detector.

FOSMIKER

 

real

Reading of FOS micrometer `R'.

FOSMIKEB

 

real

Reading of FOS micrometer `B'.

FOSMIKES

 

real

Reading of FOS micrometer `S'.

 

This packet is named ids.

PAOFFSET is an ING standard. It defines how far the slit position-angle is offset from the telescope's sky PA.

13 Cassegrain-A&G-box packet

 

Keyword

Data type

Meaning

AGTVPOSX

real

TV's x-position in metres.

AGTVPOSY

real

TV's y-position in metres.

AGTVFILT

character

Name of TV filter.

AGTVSHUT

character

State of TV shutter: `OPEN' or `SHUT'.

AGPOSX

real

x-position of autoguider probe in metres.

AGPOSY

real

y-position of autoguider probe in meters.

ASNDFILT

character

Name of ND filter in the beam above the slit.

ASCFILT

character

Name of colour filter in the beam below the slit.

FLIPMPOS

character

Position of `flip' mirror: `IN" or `OUT'.

AGARCLMP

character

Name of arc lamp in use (`NONE' if all lamps are off).

AGARCND

character

Name of ND filter in front of arc lamp.

COMPMPOS

character

Position of comparison mirror: `IN' or `OUT'.

 

This packet is named cagb.

Appendix A. Document History

Issue 1.1 22/12/94 First (incomplete) issue.

Issue 1.2 09/01/95 Description of image-size packet added (this changed the section numbering). In the observation packet, details of CTYPEn, CRPIXn, CDELTn, CROTAn altered. In the telescope packet, details of RA, DEC, RADVEL, EQUINOX, ZDSTART, ZDEND, altered; EPOCH added. In the CCD packet, details of CCDWxOn, CCDxPIXE altered; WINSECn added; notes defining CCDSEC, TRIMSEC, etc. changed. In the meterological packet, details changed for DIMM, PRESSURE, DUSTDENS, SKYBRGHT; METxOLD added.

Issue 2.1 20/06/96 Major changes after review by P. Bunclark, J. Lewis and G. Rixon. Marker introduced for end of ING-supplied header. BZERO corrected to floating point. FITSVER changed to SYSVER. FSTATION, DISPAXIS deleted and DATEARCH introduced. WCS packet split off from observation packet. LATITUDE, LONGITUD and SLATEL added. Corrections to CAT-EQUI, CAT-EPOC and TELFOCUS. UTOBS, EPOCH, ZDSTART, ZDEND, AMSTART, AMEND, MNTPATA, MNTPAEND, PAOFFSET, DAAZSTART and DAZEND all deleted. ZD and DOMEAZ added. Definition of AIRMASS changed. CCD packet split into Exposure, CCD and CCDPROC packets. WFC packet completely re-written. TEMPTUBE moved to the telescope packet.PFC packet (for the old PFCU) deleted.

Issue 3.1 1996-10-02 Descriptions of the IDS and CAGB packets were added. There is no longer a separate packet for FOS-1. The definition of the interface is now complete.

Issue 3.2 1997-03-24 The formal names are defined for all packets. SECPPIX was added to the wfc packet. The descriptors XXXSEC were removed from the packet ccd (they are now in ccdproc).

Issue 3.3 1997-09-12 The specification was updated following review of an IDS header from system s4.1a.

S TELESCOPE, INSTRUME and DETECTOR were moved from observation to telescope, ids/wfc and ccd packets respectively.

S DATE-OBS was moved from observation to exposure and its formatting rules were extended to the new FITS convention.

S RUN was moved to the top of observation to match established practice.

S PREFLASH was moved from exposure to ccd.

S READAXI was deleted from ccd.

S READAXI in ccdproc was renamed READAXIS.

S SLTSKYPA was deleted from ids and PAOFFSET was added.

S DEKPOS is now the name of the dekker position, not the encoder value (this recognizes established practice).

S CAMFOCUS is deleted from ids. The IDS has no focus drive other than the collimator drive.

S GRATBLAZE and CENWAVE are changed from Ângstroms to nm to conform with IAU and FITS standards.

S DISPERSI was added to ids.

S ASCOLFILT was corrected to ASCFILT in ids.