Hi all

Hope you can help me on this one.

I have the Biassec and Trimsec defined in the fits headers of my data. Example:

BIAS_001.fits[385,576][ushort]: Bias
No bad pixels, min=0., max=0. (old)
Line storage mode, physdim [385,576], length of user area 2673 s.u.
Created Wed 14:03:22 27-Jun-2007, Last modified Wed 14:03:42 27-Jun-2007
Pixel file "BIAS_001.fits" [ok]
EXTEND  =                    T / File may contain extensions
BSCALE  =           1.000000E0 / REAL = TAPE*BSCALE + BZERO
BZERO   =           3.276800E4 /
ORIGIN  = 'NOAO-IRAF FITS Image Kernel July 2003' / FITS file originator
DATE    = '2007-06-27T12:03:22' / Date FITS file was generated
IRAF-TLM= '14:03:42 (27/06/2007)' / Time of last modification
COMMENT   FITS (Flexible Image Transport System) format defined in Astronomy and
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.
OBJECT  = 'Bias    '           / Name of object
EXPTIME =                0.001 / Exposure time in seconds
EXPTYPE = 'BIAS    '           / Type of image
FILTER  = 'C       '           / Filter used
RA      = '10h58m27.2s'        / hh:mm:ss.ss
DEC     = '-29d01m52s'         / dd:mm:ss.ss
EPOCH   = '2007.0  '           / Epoch
DATE-OBS= '2007-6-12'          / UT of start of exp
TIME-OBS= '15:57:33'           / UT of start of exp
MJD-OBS =     2454264.16497462 / JD at start of exp
HA      = '00:00:07'           / hh:mm:ss.ss
AIRMASS =                   1. / Airmass at start of exposure
INSTRUME= 'Alta-U55'           / Camera Model
SET-TEMP=            -25.02435 / CCD temperature setpoint in C
CCD-TEMP=          -29.7911835 / CCD temperature in C
OBSERVAT= 'Boyden  '
RDNOISE =                   13
GAIN    =                  3.8
TRIMSEC = '[10:384,2:575]'
BIASSEC = '[384:385,2:575]'
UT      =             15.95917

All the fits headers have the required data.

I then combine the biasframes using zerocombine without processind the data. The biasmaster header is also correct.

But when I then run ccdproc with the following settings

ccdproc (img, ccdtype = "", fixpix-, overscan+,	trim+, biassec="image", trimsec="image", zerocor+, darkcor-, flatcor-, illum-, fringe-, zero=biasmaster)

it gives me the following error

boyden> biasred
The biasframes to be combined (biaslist.lis): 
The images to be reduced (DARK1_001.fits): 
z1=2225.99 z2=2231.743
Process images (yes): 
ERROR: Bias section not specified or given as full image
  "darkcor-, flatcor-, illum-, fringe-, zero=biasmaster)"
     line 93: boyden$biasred.cl
     called as: `biasred ()'

If someone could maybe tell me where the error could be :?

Note: The sections on "biasred" is because I run the reduction process through a script. See http://iraf.net/phpBB2/viewtopic.php?t=86036&highlight=

Regards
Pat

Hi

Figured out my error. Just defined the BIASSEC incorrectly.

I was in a bit of a panic to finish the data analysis. Sorry for that.
:oops:

Thanx
Pat

Hi all.

Doing new data analysis and got some strange results. Maybe found the source of my previous data-analysis errors... ... but that is a long story.

The problem that I have is that for my data there isn't really a TRIMSEC. But there is a BIASSEC. That is -> In the image header the values for TIMSEC is [0:385,0:576] and the BIASSEC is [0:17,0:576].....

When I run the biasreduction it gives me a TRIMSEC and BIASSEC error. Looks like they are defined incorrectly.....

When I change the 0 to a 1 in the TRIMSEC and BIASSEC values then the trim and overscan tasks runs correctly, but then they mess up the ress of my dataframes. For instance, my flatframes goes from looking like normal flats with a few "donut pits" for the dust bunnies to "inverted frames with peaks where the donut pits were, and completely incorrect data values. :x

I do not know exactly whether I am defining something wrong, or whether I sould just leave out the trim and overscan processes...

If someone could maybe help me on this... PLEASE!

Thanx
Pat

Hi Pat,

I don't see off-hand what would cause your data to appear messed up. Yes your original sections were wrong but if you set them right I would not expect anything funny.

Since basic CCD calibration is just a series of arithmetic operations you might just try to do each step, skipping the overscan, to see what things should look like. CCDPROC is very useful to automate things and do all the record keeping but what I mean for testing is to take the flat frame and bias frame and just manually subtract one from the other. Probably just looking at the frames will be enough to see if something funny would happen when applying a bias to a flat.
Yes you could turn over the overscan and trimming to avoid the problems with
those sections.

I am just rambling here. As I said I see that you are doing anything particularly wrong and it would take looking at data for me to be able to say much more.

Yours,
Frank Valdes

Hi Frank

I ran through the reductions with trim and overscan turned off, and the data looks good.

Thing is, if it becomes necessary to use trim and overscan, does ccdproc acept 0 values in the vector. -> TRIMSEC = [0:100,0:100] or does it only acept values >= than 1. That is what is buggering up the whole process.

Thanx
Pat

Pat,

The sections are IRAF sections refering to regions of the image. IRAF sections, and anything to do with pixel coordinates, are one-indexed. So the first pixel in and image is (1,1). This means image sections cannot start at zero but must start at 1 or above. Of course they should also not refer to pixels beyond the edges of the image. CCDPROC has special features to match images since it is possible to have different trims between object and flat field or even have subraster readouts. These are more sophisticated but are controlled by the various section parameters including DATASEC and CCDSEC. If these are inconsistent it is possible for funny things to happen. However, normally if there is something wrong there is a mismatch in the sizes of the sections and some error is written.

While I don't have a lot of time to devote to this if you want to send me header listings of all images involved and the CCDPROC parameters I can try and spot inconsistencies and misunderstandings.

Frank

Hi Frank

You explenation was sufficiant thanx. :D I now have a clearer understanding of how the different image sections work. Thanx for your time and effort for listening and helping an inexperienced photometry student.

Regards
Pat