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Re: Fits Headers Again
2 more cents...
What about the camera cooler/chip temperature - useful for image
processing if the dark frame is lost, damaged, or stolen. Also having a
record of where the telescope thought is was pointed (RA & DEC) + LST or
Hour Angle can be very useful for analysis of the telescope performance/
trouble shooting / everything else.
Also, from the image processing standpoint...
Presumably, these huge data sets that will be collected by the program
will mostly be processed/analyzed by computer and most of the time
Humans won't be viewing the fits headers directly.
Given this: From a programming stand point, dealing with number formats
of time, date, or coordinates given in human readable formats, such as
HH:MM:SS / DD MM SS / 2000-4-25, requires extra amount of work in
program development as they typically have to be converted to decimal
formats to be operated on. So the thought here is that a few key things
should be stored as floating point numbers instead/in addition to
traditional human connivance formats.
Maybe this stuff has been already been considered and I missed it, but I
thought I should throw it down on the table anyway.
Doug Welch wrote:
> Hi Tom,
> It needs an EPOCH or an EQUINOX (or both).
> On Sat, 10 Mar 2001, Tom Droege wrote:
> > Below is some stuff copied (now directly) out of TN-67. My plan is to make
> > two files. One is the fixed stuff and one varies run by run. My question
> > is, what is a fits extension? Is it everything after the: EXTEND
> > = T/ line below or is it something else?
> > Tom Droege
> > Recommendations:
> > · Switch RA and DEC axis.
> > · CTYPE1 and CTYPE2 must read 'RA---TAN' and 'DEC--TAN', respectively.
> > · EXPOSURE keyword must be present, with correct exposure time in
> > secomds.
> > · It's better to use reference pixels in the middle of image: CRPIX1,
> > CRPIX2=1024.
> > · CDELT1 and CDELT2 are missing now, they must contain pixel
> > increment at the reference pixel. In simpler terms, pixel size with
> > possible negative sign if coordinate is decreasing with increasing pixel
> > coordinates. Size is expressed in decimal degrees.
> > · Keyword IMAGETYP with possible values 'object', 'dark', 'flat' and
> > 'zero' should be included if IRAF proceessing of images will be used.
> > · Change DATE-OBS to include time as well, not only date.
> > · Inclusion of the following keywords may be useful
> > · RDNOISE in electrons.
> > · GAIN in electrons/ADU.
> > · CCD-TEMP or CAMTEMP with temperature in degrees Celsius.
> > · AIRMASS
> > Example of enhanced header after star matching (image H3R1659-826.fts):
> > SIMPLE = T / file does conform to FITS standard
> > BITPIX = 16 / number of bits per data pixel
> > NAXIS = 2 / number of data axes
> > NAXIS1 = 2043 / length of data axis 1
> > NAXIS2 = 2037 / length of data axis 2
> > EXTEND = T / FITS dataset may contain extensions
> > COMMENT FITS (Flexible Image Transport System) format defined in Astronomy an
> > COMMENT Astrophysics Supplement Series v44/p363, v44/p371, v73/p359, v73/p365
> > COMMENT Contact the NASA Science Office of Standards and Technology for the
> > COMMENT FITS Definition document #100 and other FITS information.
> > CTYPE1 = 'RA---TAN' / Inserted by fitsblink
> > CRVAL1 = 2.263508539420E+02 / Inserted by fitsblink
> > CRPIX1 = 1.021500000000E+03 / Inserted by fitsblink
> > CROTA1 = 8.974035779811E+01 / Inserted by fitsblink
> > CTYPE2 = 'DEC--TAN' / Inserted by fitsblink
> > CRVAL2 = 1.723629532873E+00 / Inserted by fitsblink
> > CRPIX2 = 1.018500000000E+03 / Inserted by fitsblink
> > CROTA2 = 8.974035779811E+01 / Inserted by fitsblink
> > BSCALE = 1.
> > BZERO = 32768.
> > LATITUDE= 42.
> > LONGITUD= -88.
> > FILTER = 'V '
> > DATE = '2000-04-25'
> > DATE-OBS= '2000-04-25'
> > UT = '07:49:52.00'
> > TIMESYS = 'UT '
> > COMMENT This file produced by TASS RawToFITS program Version 1.1
> > CDELT1 = 2.150392161597E-03 / Inserted by fitsblink
> > CDELT2 = 2.150050490463E-03 / Inserted by fitsblink
> > IMAGETYP= 'object ' / insert_keywords
> > EXPOSURE= 1.500000E+01 / insert_keywords
> > EXPTIME = 1.500000E+01 / insert_keywords
> > MATCHED = T / Inserted by fitsblink
> > END
> Douglas L Welch | Office/voicemail (905) 525-9140 x23186
> Physics & Astronomy | FAX (905) 546-1252
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