The 2MASS Atlas and Quicklook Images are in the same format but the Quicklook Images are lossy-compressed. With the exception of the "bitpix" keyword, headers are identical.
An actual 2MASS Atlas Image header may be found here.
Click on the underlined Field Names for more detail on those parameters.
| Field Name | Format | Units | null | Description | |
|---|---|---|---|---|---|
| Primary Fits Information | |||||
| bitpix | %20d | --- | no | -32 => 32 bit IEEE floating point data (Atlas Images)
16 => 16 bit integer data (lossy compressed Quicklook Images) |
|
| naxis | %20d | --- | no | (always= 2) 2 dimensional image | |
| naxis1 | %20d | --- | no | Number of columns in image | |
| naxis2 | %20d | --- | no | Number of lines in image | |
| Observatory Data Identifiers | |||||
| ordate | %20s | --- | no | Observation reference date in the YYMMDD. This is the UT day value at the start of operations for the night on which the source was observed. Because the UT day incremented during the night at CTIO, the actual UT observation date for a source can differ from this value by one day. | |
| daynum | %20d | day | no | Sequential survey day number, where day 1 is defined to be 1 March 1997 UT. Observations were started at Mt. Hokpins on daynum=109 (7 June 1997 UT) and at CTIO on daynum=384 (19 March 1998 UT). | |
| fn_prfx | %20s | --- | no | Observatory Filename Prefix | |
| type | %20s | --- | no | Scan type: dar (dark), flt (flat), sci (survey), cal (calibration), or tst (test) | |
| scanno | %20d | --- | no | Nightly scan number | |
| scandir | %20s | --- | no | Scan Direction: n (north), s (south) | |
| strip_id | %20d | --- | no | 2MASS Tile number. | |
| positnid | %20s | --- | no | Observatory Scan Position Identifier (Hddhhmm -> H = hemisphere, dd = dec at tile center, hhmm = hours and minutes at tile center) | |
| origin | %20s | --- | no | 2MASS Survey Camera | |
| Projection and Location Information | |||||
| ctype1 | %20s | --- | no | Orthographic Projection | |
| ctype2 | %20s | --- | no | Orthographic Projection | |
| crpix1 | %20f | pix | no | Column Coordinate at Image Center (crval1/crval2) | |
| crpix2 | %20d | pix | no | Line Coordinate at Image Center (crval1/crval2) | |
| crval1 | %20f | deg | no | Right Ascension at Image Center (J2000) | |
| crval2 | %20f | deg | no | Declination at Image Center (J2000) | |
| crota2 | %20f | deg | no | Twist about Image Center, +AXIS2 WofN (J2000) | |
| cdelt1 | %20f | deg | no | Axis1 Pixel Size (=1 arcsec) | |
| cdelt2 | %20f | deg | no | Axis2 Pixel Size (=1 arcsec) | |
| Calibration and Auxillary Image Information | |||||
| usxref | %20f | asec | no | 2MASS U-scan X Coordinate at Image Center | |
| usyref | %20f | asec | no | 2MASS U-scan Y Coordinate at Image Center | |
| skyval | %20f | dn | no | Modal Sky Estimate for Image (image dn) | |
| skysig | %20f | dn | no | Point Source Filtered Noise Estimate for Image (image dn) | |
| magzp | %20f | mag | no | Calibrated Zero Point for Image (magnitudes) | |
| calid | %20s | --- | no | Calibration Identifiers for Image | |
| seesh | %20f | --- | no | Seeing Shape Parameter for Image (image dn) | |
| dxfs | %20f | asec | no | Cross-scan Frame Step for Image | |
| dyfs | %20f | asec | no | In-scan Frame Step for Image | |
| pixnam | %20s | --- | no | PIXPHOT Processing Namelist Configuration Identifier | |
| QT0227 | %20f | --- | no | Image Histogram 2.27 Percentile (Image DN) | |
| QT0668 | %20f | --- | no | Image Histogram 6.68 Percentile (Image DN) | |
| QT1586 | %20f | --- | no | Image Histogram 15.86 Percentile (Image DN) | |
| QT3085 | %20f | --- | no | Image Histogram 30.85 Percentile (Image DN) | |
| QT5000 | %20f | --- | no | Image Histogram 50.00 Percentile (Image DN) | |
| QT6914 | %20f | --- | no | Image Histogram 69.14 Percentile (Image DN) | |
| QT8413 | %20f | --- | no | Image Histogram 84.13 Percentile (Image DN) | |
| QT9331 | %20f | --- | no | Image Histogram 93.31 Percentile (Image DN) | |
| QT9772 | %20f | --- | no | Image Histogram 97.72 Percentile (Image DN) | |
| Auxillary Observatory Information | |||||
| base | %20d | ms | no | Pixel Dwell Time (milliseconds) | |
| wavef_p | %20s | --- | no | Secondary Waveform Data File | |
| timer0 | %20d | ms | no | Read1 Time (milliseconds) | |
| timer1 | %20d | ms | no | Read2-Read1 Time (milliseconds) | |
| timer2 | %20d | ms | no | Secondary Settling Time (milliseconds) | |
| icsversn | %20s | --- | no | ICS Script Version | |
| schedver | %20s | --- | no | Scan Scheduler Version | |
| scriptfn | %20s | --- | no | Script Template Filename | |
| scrptver | %20s | --- | no | Script Template Version | |
| ut_off1 | %20f | sec | no | UT Offset - SOS to Frame 1 | |
| xs_off1 | %20f | asec | no | X-scan Offset - SOS to Frame 1 | |
| is_off1 | %20f | asec | no | In-scan Offset - SOS to Frame 1 | |
| xs_off2 | %20f | asec | no | X-scan Offset - EOS to End Frame | |
| is_off2 | %20f | asec | no | In-scan Offset - EOS to End Frame | |
| focus | %20d | --- | no | Telescope Focus Setting | |
| numfrms | %20d | --- | no | Number of Frames in Scan | |
| skiprdos | %20d | --- | no | Number of Frames Skipped at Start of Scan | |
| telname | %20s | --- | no | Telescope Location - Hopkins or CTIO | |
| filter | %20s | --- | no | Wavelength Band - j, h, or k (J, H, or Ks) | |
| ut_date | %20s | --- | no | UT Date of Scan (YYMMDD) | |
| ut | %20s | --- | no | UT Time of Scan (HH:MM:SS.SSS) | |
| amass_fc | %20s | --- | no | Approximate Airmass at Image Center | |
| ut_date | %20s | --- | no | UT Date of Scan (YYMMDD) | |
| Auxillary Observatory Information at Start Of Scan | |||||
| date_sos | %20s | --- | no | UT Date at Start of Scan (YYMMDD) | |
| equinox | %20s | --- | no | Equinox at Start of Scan | |
| am_sos | %20f | --- | no | Airmass at Start of Scan | |
| zd_sos | %20f | deg | no | Zenith Distance at Start of Scan | |
| ha_sos | %20s | --- | no | Hour Angle at Start of Scan (HH:MM:SS.SS) | |
| ut_sos | %20s | --- | no | UT at Start of Scan (HH:MM:SS.SS) | |
| st_sos | %20s | --- | no | Sidereal Time at Start of Scan (HH:MM:SS.SS) | |
| ra_sos | %20f | --- | no | Scan Reference RA J2000 (HH:MM:SS.S) | |
| dec_sos | %20f | --- | no | Scan Reference Declination J2000 (DD:MM:SS.S) | |
| wspd_sos | %20d | --- | no | Wind Speed at Start of Scan (not implemented) | |
| wdir_sos | %20d | --- | no | Wind Direction at Start of Scan (not implemented) | |
| see_sos | %20d | --- | no | Seeing at Start of Scan (not implemented) | |
| bar_sos | %20d | in Hg | no | Barometric Pressure at Start of Scan | |
| airt_sos | %20f | deg C | no | Air Temperature at Start of Scan | |
| telt_sos | %20f | deg C | no | Telescope Temperature at Start of Scan | |
| Auxillary Observatory Information at End Of Scan | |||||
| date_eos | %20s | --- | no | UT Date at End of Scan (YYMMDD) | |
| am_eos | %20f | --- | no | Airmass at End of Scan | |
| zd_eos | %20f | deg | no | Zenith Distance at End of Scan | |
| ha_eos | %20s | --- | no | Hour Angle at End of Scan (HH:MM:SS.SS) | |
| ut_eos | %20s | --- | no | UT at End of Scan (HH:MM:SS.SS) | |
| st_eos | %20s | --- | no | Sidereal Time at End of Scan (HH:MM:SS.SS) | |
| ra_eos | %20f | --- | no | Scan Reference RA J2000 (HH:MM:SS.S) | |
| dec_eos | %20f | --- | no | Scan Reference Declination J2000 (DD:MM:SS.S) | |
| wspd_eos | %20d | --- | no | Wind Speed at End of Scan (not implemented) | |
| wdir_eos | %20d | --- | no | Wind Direction at End of Scan (not implemented) | |
| see_eos | %20d | --- | no | Seeing at End of Scan (not implemented) | |
| bar_eos | %20d | in Hg | no | Barometric Pressure at End of Scan | |
| airt_eos | %20f | deg C | no | Air Temperature at End of Scan | |
| telt_eos | %20f | deg C | no | Telescope Temperature at End of Scan | |
| aryt_eos | %20f | deg C | no | Array Temperature at End of Scan | |
[Last Updated: 2003 March 14, by Gene Kopan & R. Cutri]