iraf.net

Hi,I met the following error when starting ccdproc: ERROR: floating point invalid operation. The only thing this time ccdproc should do is zero and flat correction on an image (to make things easier), but with no luck. The output of the process using d_trace is as follows:[code:1:be7e75df9c]
ecl> ccdproc
----- task cl - line 0 (CALL) -----
0 0+5: call ccdproc
0 5+3: exec
----- exec external task ccdproc - line 0 -----
----- connect to noaobin$x_ccdred.e -----
ccdproc\noutput="V405AND_V_0234.fits"\nccdtype=" "\n
max_cache=0\nnoproc=no\nfixpix=no\noverscan=no\ntrim=no\n
zerocor=yes\ndarkcor=no\nflatcor=yes\nillumcor=no\n
fringecor=no\nreadcor=no\nscancor=no\nreadaxis="line"\n
fixfile=" "\nbiassec="[5:10,15:1150]"\n
trimsec="[25:790,15:1150]"\n
zero="/media/disk/rcc/bias3-0/Zero.fits"\ndark=" "\n
flat="*sf*"\nillum=" "\nfringe=" "\nminreplace=1.\n
scantype="shortscan"\nnscan=1801\ninteractive=no\n
function="legendre"\norder=1\nsample="*"\nnaverage=1\n
niterate=1\nlow_reject=3.\nhigh_reject=3.\ngrow=0.\nmode="q"\n
$nargs=0\n
--------------------------------
----- task ccdproc - line 53 (INSPECT) -----
53 11+5: inspect images
List of CCD images to correct (v405and_V_0234.fits):
53 16+3: end
----- task ccdproc - line 54 (INSPECT) -----
54 11+6: inspect instrument
54 17+3: end
----- task ccdproc - line 55 (INSPECT) -----
55 11+5: inspect ssfile
55 16+3: end
----- task ccdproc - line 56 (INSPECT) -----
56 11+5: inspect ssfile
56 16+3: end
----- task ccdproc - line 57 (INSPECT) -----
57 11+5: inspect ssfile
57 16+3: end
----- task ccdproc - line 58 (INSPECT) -----
58 11+6: inspect pixeltype
58 17+3: end
----- task ccdproc - line 59 (INSPECT) -----
59 11+6: inspect pixeltype
59 17+3: end
----- task ccdproc - line 60 (INSPECT) -----
60 11+5: inspect verbose
60 16+3: end
----- task ccdproc - line 61 (INSPECT) -----
61 11+5: inspect logfile
61 16+3: end
----- task ccdproc - line 62 (INSPECT) -----
62 11+5: inspect ssfile
62 16+3: end
----- task ccdproc - line 63 (INSPECT) -----
63 11+5: inspect verbose
63 16+3: end
----- task ccdproc - line 64 (INSPECT) -----
64 11+5: inspect logfile
64 16+3: end
----- task ccdproc - line 65 (CALL) -----
65 11+5: call error
65 16+6: pushconst 502
65 22+4: posargset 0
65 26+15: pushconst `floating point invalid operation'
65 41+4: posargset 1
65 45+3: exec
----- exec builtin error : line 65 -----
----- disconnect noaobin$x_ccdred.e -----
ERROR: floating point invalid operation
cl_error: abort=1 trace=1 flpr=1
cl_error: code=502 do_err=1 errtype=1/1 task='cl'
[/code:1:be7e75df9c]I suspected a division by zero, but minreplace is set to 1, so this shouldn't happen... Do you have any ideas what to do?Thanks,Chris

Chris,There's not a lot of detail to go on, perhaps Frank will have a suggestion as well. I did notice that you have parameters specified as e.g. dark=" " rather than dark="" however these strings shouldn't matter is that kind of correction isn't enabled. Still, a string with a space is not the same as a "empty" string denoted by two quotes.Otherwise, is there something unusual in the image, e.g. non-standard BSCALE/BZERO header values? Can other tasks such as IMSTAT correctly read the image or do they similarly (implying a problem with the data and/or the FITS image kernel)? Can you use a task like IMARITH to manually do the dark/zero correction e.g. with a simple subtraction?There aren't any known issues with CCDPROC that could explain this. If you still have problems please post your IRAF and OS version. Hope this helps.Cheers,
-Mike

I'm getting quite confused now... The same problem happened both on my PC and on my laptop with the same images. Finally I experimented with only one image and one flat frame with no luck. Somehow, the problem was solved on my laptop - I have no clue what could happen. I was trying to make a config set of setinstr on my laptop to make life easier - could this change anything?
The imstat and imarith task both run well on both machines, while ccdproc still fails on the pc. There are no bscale/bzero fields in the header.
The OS is the same on both machines: (K)ubuntu linux 7.10 with 2.6.22-14 kernel. The IRAF version is PC-IRAF Revision 2.13-BETA2 .

Well, I tried with a set of re-combined flat images, and it finally worked on both machines. I still don't get what the problem was
As far as I remember, I've tried this thing also earlier... :shock:

It seems I'm doomed... The problem is the same, again.
I tried to run ccdproc for only one frame using an unprocessed flat, it's OK. Now when trying with a bias-corrected flat frame (just one flat image, not a combined one), the floating-point error is back.
The bias frame is OK as far as I see, I have used it already...
Maybe I should sacrifice a black goat or whatever...

I'll ask Frank to have a look, I'm out of ideas and the goat thing never worked for me. Most often this is something to do with the data, or a problem with the parameters being used (e.g. an invalid uparm directory). You mentioned SETINSTRUMENT which is mostly related to the header keyword translation/use, is it possible this was somehow reset between uses?Cheers,
-Mike

SETINSTR couldn't be reset, unluckily. I was experimenting with that package between the first unsuccessful and the second (successful) reduction, so I thought that it will solve the problem. However on the third run it didn't work
(Just to mention, we don't have an SETINSTR configured for our site, it has to be done by hand...)I thought that the frame sizes could be somehow different, but that's not the case, either.

Hi,The first confusion to address is what "minreplace" does. It is applied only when a flat field is processed. When a flat field is being applied to an image there is not checking for zero (or near zero) in the flat field. This is for efficiency. So you can get the same effect by doing an imreplace on the flat field, with some suitable minimum value depending on whether the flat is normalized or not, and then applying the flat field with ccdproc.In your output I don't see any log info (i.e. what you get with ccdred.verbose=yes). This may be because the verbose flag is not set. The only usefulness of this is that it would pinpoint whether the exception occurs before or after the log. If after then it could very well be during the application of the flat field.I don't think the instrument translation file would affect things though there are a few circumstances (applying a dark would be one) when it could.I guess sending the output of imstat and the log output might be useful. Otherwise the only further option is getting the data.Frank Valdes

Well, this problem seems to be solved, I think There was a line of the CCD field that I didn't notice, and has much lower ADUs than the others (but not on all frames) which caused all the problems, and I didn't recognise the presence of it.
So after all PEBCAT( Problem Exists Between Chair and Terminal) case occurred

Hi,I have also encountered the same problem. The message are listed below:ccdred> ccdproc
List of CCD images to correct (dark.00000001.DARK.FIT):
dark.00000001.DARK.FIT: Oct 30 18:21 Zero level correction image is ../bias/zero.fits
ERROR: floating point invalid operationAnd when I make a command ls -al, I find there is generating 'extra' image, tmp9498a.fits. Could somebody help me to solve the problem? hymong@Mars:~/test/dark$ ls -al
total 94492
drwxr-xr-x 2 hymong hymong 4096 2007-10-30 18:21 .
drwxr-xr-x 8 hymong hymong 4096 2007-10-25 14:23 ..
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark.00000001.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark.00000002.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark.00000003.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark.00000004.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark.00000005.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark_CS_3min_.00000001.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark_CS_3min_.00000002.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark_CS_3min_.00000003.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark_CS_3min_.00000004.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark_CS_3min_.00000005.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark_CS_3min_.00000006.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark_CS_3min_.00000007.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark_CS_3min_.00000008.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark_CS_3min_.00000009.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-30 17:50 dark_CS_3min_.00000010.DARK.FIT
-rw-r--r-- 1 hymong hymong 435 2007-10-30 17:48 d.list
-rw-r--r-- 1 hymong hymong 3058 2007-10-30 18:21 logfile
-rw-r--r-- 1 hymong hymong 6436800 2007-10-30 18:15 tmp9498a.fitsThanks!!
hymong

The tmp file is a common result of an unexpected crash of the program. All processing is done to a temporary image and then, when successful, the temporary image replace the input image. This protects the input data and is a good thing though it does have the effect of leaving behind a file if there is a crash. You can just delete the file.As to why you are getting an error, this kind of error has to do with unusually small or large numbers. The only way to diagnose the cause is with a debugger. However, if you do an imstat of the images and look at the min/max fields this often shows signs of the unusual numbers.Frank Valdes

Dear Frank,Thanks for your explanation and helps very much I have understood the processing of IRAF.As for the error, I have done the command imstat of the images. And the result lists below:ccdred> imstat
List of input images (*.FIT)
# IMAGE NPIX MEAN STDDEV MIN MAX
dark.00000001.DARK.FIT 3214848 106.2 89.18 63. 51722.
dark.00000002.DARK.FIT 3214848 106.2 89.37 60. 51709.
dark.00000003.DARK.FIT 3214848 107.4 89.35 66. 51726.
dark.00000004.DARK.FIT 3214848 107.3 89.39 62. 51707.
dark.00000005.DARK.FIT 3214848 105.4 89.45 62. 51773.
dark_CS_3min_.00000001.DARK.FIT 3214848 106.5 89.8 64. 51653.
dark_CS_3min_.00000002.DARK.FIT 3214848 107.3 89.72 63. 51678
dark_CS_3min_.00000003.DARK.FIT 3214848 106.5 89.78 63. 51688.
dark_CS_3min_.00000004.DARK.FIT 3214848 106.3 90.12 63. 51655.
dark_CS_3min_.00000005.DARK.FIT 3214848 106.8 90.23 64. 51761.
dark_CS_3min_.00000006.DARK.FIT 3214848 106.6 90.01 60. 51692.
dark_CS_3min_.00000007.DARK.FIT 3214848 106.9 89.75 63. 51704.
dark_CS_3min_.00000008.DARK.FIT 3214848 106.3 89.77 61. 51723.
dark_CS_3min_.00000009.DARK.FIT 3214848 107.6 89.83 66. 51679.
dark_CS_3min_.00000010.DARK.FIT 3214848 106.2 89.81 62. 51695.So it seems that it didn't show signs of the unusual numbers in the min/max fields. Could you suggest any other causes of the problem?Thanks!!
hymong

Hi Hymong,Please also do an imstat on "../bias/zero.fits" which is the file that ccdproc was trying to apply when the error occured.Frank

Hi Frank,The result of doing imstat on "../bias/zero.fits" lists below:ccdred> imstat zero.fits
# IMAGE NPIX MEAN STDDEV MIN MAX
zero.fits 3214848 100.5 2.391 88.11 825.4hymong

Try using ccdlist and send me the output. If you have set things up so that the ccdproc can identify dark images then it will try and figure out the exposure time (used for scaling darks). There is some possiblity that a problem with this causes the floating point problem.Frank

Hi Frank,The results of bias and dark parts are below:hymong@Mars:~/test/bias$ ls -al
total 75560
drwxr-xr-x 2 hymong hymong 4096 2007-10-31 11:58 .
drwxr-xr-x 8 hymong hymong 4096 2007-10-25 14:23 ..
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 11:55 bias_CS_.00000001.BIAS.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 11:55 bias_CS_.00000002.BIAS.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 11:55 bias_CS_.00000003.BIAS.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 11:55 bias_CS_.00000004.BIAS.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 11:55 bias_CS_.00000005.BIAS.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 11:55 bias_CS_.00000006.BIAS.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 11:55 bias_CS_.00000007.BIAS.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 11:55 bias_CS_.00000008.BIAS.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 11:55 bias_CS_.00000009.BIAS.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 11:55 bias_CS_.00000010.BIAS.FIT
-rw-r--r-- 1 hymong hymong 270 2007-10-31 11:54 b.list
-rw-r--r-- 1 hymong hymong 982 2007-10-31 11:58 logfile
-rw-r--r-- 1 hymong hymong 12864960 2007-10-31 11:58 zero.fitsccdred> ccdlist *.* l+
Warning: Cannot open image (b.list)
bias_CS_.00000001.BIAS.FIT[2148,1472][ushort][zero][]:bias_CS_.00000002.BIAS.FIT[2148,1472][ushort][zero][]:bias_CS_.00000003.BIAS.FIT[2148,1472][ushort][zero][]:bias_CS_.00000004.BIAS.FIT[2148,1472][ushort][zero][]:bias_CS_.00000005.BIAS.FIT[2148,1472][ushort][zero][]:bias_CS_.00000006.BIAS.FIT[2148,1472][ushort][zero][]:bias_CS_.00000007.BIAS.FIT[2148,1472][ushort][zero][]:bias_CS_.00000008.BIAS.FIT[2148,1472][ushort][zero][]:bias_CS_.00000009.BIAS.FIT[2148,1472][ushort][zero][]:bias_CS_.00000010.BIAS.FIT[2148,1472][ushort][zero][]:zero.fits[2184,1472][real][zero][]:
exposure=0 darktime=0hymong@Mars:~/test/dark$ ls -al
total 94456
drwxr-xr-x 2 hymong hymong 4096 2007-10-31 13:26 .
drwxr-xr-x 8 hymong hymong 4096 2007-10-25 14:23 ..
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark.00000001.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark.00000002.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark.00000003.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark.00000004.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark.00000005.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark_CS_3min_.00000001.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark_CS_3min_.00000002.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark_CS_3min_.00000003.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark_CS_3min_.00000004.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark_CS_3min_.00000005.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark_CS_3min_.00000006.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark_CS_3min_.00000007.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark_CS_3min_.00000008.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark_CS_3min_.00000009.DARK.FIT
-rw-r--r-- 1 hymong hymong 6433920 2007-10-31 13:26 dark_CS_3min_.00000010.DARK.FIT
-rw-r--r-- 1 hymong hymong 435 2007-10-31 13:26 d.list
-rw-r--r-- 1 hymong hymong 3058 2007-10-30 18:21 logfileccdred> ccdlist *.* l+
Warning: Cannot open image (d.list)
dark.00000001.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark.00000002.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark.00000003.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark.00000004.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark.00000005.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark_CS_3min_.00000001.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark_CS_3min_.00000002.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark_CS_3min_.00000003.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark_CS_3min_.00000004.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark_CS_3min_.00000005.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark_CS_3min_.00000006.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark_CS_3min_.00000007.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark_CS_3min_.00000008.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark_CS_3min_.00000009.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correction
dark_CS_3min_.00000010.DARK.FIT[2184,1472][ushort][dark][]: [TO BE DONE] Zero level correctionhymong

Hi Frank,It is really weird. I just re-login cl and re-do the process. This time it works well to do darkcombine. However, I encountered another error message while I would like to get pure-flat images. Following I list my procedure for your reference:ccdred> cd /home/hymong/test/bias
ccdred> ls *.FIT > b.list
ccdred> ccdhedit @b.list IMAGETYP "zero"
ccdred> zerocombine @b.list output=zero combine=average ccdtype=zero process=no rdnoise=8 gain=1.4
ccdred> cd ../dark
ccdred> ls *.FIT > d.list
ccdred> ccdhedit @d.list IMAGETYP "dark"
ccdred> ccdproc @d.list ccdtype=dark fixpix=no oversca=no trim=no zerocor=yes darkcor=no flatcor=no zero=../bias/zero.fits
ccdred> darkcombine @d.list output=dark combine=average ccdtype=dark process=no scale=exposure rdnoise=8 gain=1.4
ccdred> cd ../flatC
ccdred> ls *.FIT > fc.list
ccdred> ccdhedit @fc.list IMAGETYP "flat"
ccdred> ccdproc @fc.list ccdtype=flat fixpix=no oversca=no trim=no zerocor=yes darkcor=yes flatcor=no zero=../bias/zero.fits dark=../dark/dark.fitsImager37.FIT: Oct 31 15.10 Zero level correction image is ../bias/zerofits
ERROR: Image header paramenter not found (exptime)Thanks,
hymong

Hi Hymong,I thought ccdlist would show the exposure time or lack of exposure time. But it looks like your problems are causes by not having an exposure time in the header, not mapping to the keyword for exposure time, or having an exposure time of zero when a non-zero value is used. As as I said, ccdproc only needs exposure times for dark calibrations. If you want to combine with scaling or weighting based on exposure time then an exposure time keyword is also needed. The usual exposure time keyword is "exptime". So maybe you need to add this to your data as appropriate. That seems to be the problem in your last message.So I hope you are on your way.Frank

Hi Frank,Thanks for your kindly helps before. I really learned a lot from youI agree with your thoughts on my problems. In the beginning, I had doubts on the missing keyword "exptime" or its value in the header. After checking my image header, I found that the keyword is "EXPOSURE" not "EXPTIME"And I checked the headers of individual dark images before doing darkcombine command:ccdred> ccdproc @d.list ccdtype=dark fixpix=no oversca=no trim=no zerocor=yes darkcor=no flatcor=no zero=../bias/zero.fits and after doing darkcombine command:ccdred> darkcombine @d.list output=dark combine=average ccdtype=dark process=no scale=exposure rdnoise=8 gain=1.4Extra fields are added to dark.fits:NCOMBINE= 15
EXPTIME = 0.
DARKTIME= 0.I have done ccdhedit to modify the value of EXPTIME below:
ccdred> ccdhedit dark.fits EXPTIME 180And re-check the header:NCOMBINE= 15
EXPTIME = 180
DARKTIME= 0. However, when I do the following command, I still got the same error message
ccdred> ccdproc @fc.list ccdtype=flat fixpix=no oversca=no trim=no zerocor=yes darkcor=yes flatcor=no zero=../bias/zero.fits dark=../dark/dark.fitsImager37.FIT: Oct 31 15.10 Zero level correction image is ../bias/zerofits
ERROR: Image header parameter not found (exptime)It seems that the problem I encountered is something wrong about the keyword "EXPOSURE" and "EXPTIME" and its value. But if it is right, why it worked well when I subtracted combined zero from each dark image to get pure-dark one by doing the command:ccdred> ccdproc @d.list ccdtype=dark fixpix=no oversca=no trim=no zerocor=yes darkcor=no flatcor=no zero=../bias/zero.fits
hymong

Hi,Thank you for your appreciation.Could you please send the output of
[code:1:af08a607c3]
lpar ccdred ccdproc darkcombine
imhead Imager37.FIT,../bias/zerofits l+
[/code:1:af08a607c3]This is confusing but we will keep trying to understand the problem.Yours,
Frank

Dear Frank,You are worthy of the honor And thanks for IRAF group to help us using the powerful software to process the astronomical images very much.Following are the output for your reference:
[code:1:24fd5da8c5]ccdred> lpar ccdred ccdproc darkcombine [/code:1:24fd5da8c5]
ccdred:
(pixeltype = "real real") Output and calculation pixel datatypes
(verbose = yes) Print log information to the standard output?
(logfile = "logfile") Text log file
(plotfile = "") Log metacode plot file
(backup = "") Backup directory or prefix
(instrument = "") CCD instrument file
(ssfile = "subsets") Subset translation file
(graphics = "stdgraph") Interactive graphics output device
(cursor = "") Graphics cursor input
(version = "2: October 1987")
(mode = "ql")
($nargs = 0)
ccdproc:
images = "@f.list" List of CCD images to correct
(output = "") List of output CCD images
(ccdtype = "flat") CCD image type to correct
(max_cache = 0) Maximum image caching memory (in Mbytes)
(noproc = no) List processing steps only?\n
(fixpix = no) Fix bad CCD lines and columns?
(overscan = no) Apply overscan strip correction?
(trim = no) Trim the image?
(zerocor = yes) Apply zero level correction?
(darkcor = yes) Apply dark count correction?
(flatcor = no) Apply flat field correction?
(illumcor = no) Apply illumination correction?
(fringecor = no) Apply fringe correction?
(readcor = no) Convert zero level image to readout correction?
(scancor = no) Convert flat field image to scan correction?\n
(readaxis = "line") Read out axis (column|line)
(fixfile = "") File describing the bad lines and columns
(biassec = "image") Overscan strip image section
(trimsec = "image") Trim data section
(zero = "../bias/zero.fits") Zero level calibration image
(dark = "../dark/dark.fits") Dark count calibration image
(flat = "") Flat field images
(illum = "") Illumination correction images
(fringe = "") Fringe correction images
(minreplace = 1.) Minimum flat field value
(scantype = "shortscan") Scan type (shortscan|longscan)
(nscan = 1) Number of short scan lines\n
(interactive = yes) Fit overscan interactively?
(function = "chebyshev") Fitting function
(order = 1) Number of polynomial terms or spline pieces
(sample = "*") Sample points to fit
(naverage = 1) Number of sample points to combine
(niterate = 1) Number of rejection iterations
(low_reject = 3.) Low sigma rejection factor
(high_reject = 3.) High sigma rejection factor
(grow = 0.) Rejection growing radius
(mode = "ql")
darkcombine:
input = "@d.list" List of dark images to combine
(output = "dark") Output dark image root name
(combine = "average") Type of combine operation
(reject = "minmax") Type of rejection
(ccdtype = "dark") CCD image type to combine
(process = no) Process images before combining?
(delete = no) Delete input images after combining?
(clobber = no) Clobber existing output image?
(scale = "exposure") Image scaling
(statsec = "") Image section for computing statistics
(nlow = 0) minmax: Number of low pixels to reject
(nhigh = 1) minmax: Number of high pixels to reject
(nkeep = 1) Minimum to keep (pos) or maximum to reject (neg
(mclip = yes) Use median in sigma clipping algorithms?
(lsigma = 3.) Lower sigma clipping factor
(hsigma = 3.) Upper sigma clipping factor
(rdnoise = "8") ccdclip: CCD readout noise (electrons)
(gain = "1.4") ccdclip: CCD gain (electrons/DN)
(snoise = "0.") ccdclip: Sensitivity noise (fraction)
(pclip = -0.5) pclip: Percentile clipping parameter
(blank = 0.) Value if there are no pixels
(mode = "ql") [code:1:24fd5da8c5]ccdred> imhead Imager37.FIT,../bias/zero.fits |+ [/code:1:24fd5da8c5]
Imager37.FIT[2184,1472][ushort]:
No bad pixels, min=0., max=0. (old)
Line storage mode, physdim [2184,1472], length of user area 1215 s.u.
Created Thu 11:41:29 01-Nov-2007, Last modified Thu 11:41:33 01-Nov-2007
Pixel file "Imager37.FIT" [ok]
EXTEND = F / File may contain extensions
BSCALE = 1.000000E0 / REAL = TAPE*BSCALE + BZERO
BZERO = 3.276800E4 /
DATE = '2007-11-01T03:41:29' / Date FITS file was generated
IRAF-TLM= '11:41:33 (01/11/2007)' / Time of last modification
BIAS = 100
ORIGIN = 'Origin '
TELESCOP= '400mm 100mm '
FOCALLEN= +4.000000000000e+002
APERTURE= +1.000000000000e+002
OBSERVER= 'Lelis1 '
DATE-OBS= '2007-03-02 '
TIME-OBS= '10:23:35 '
CCDSFPT = 4
CCDSUBFL= 0
CCDSUBFT= 0
CCDXBIN = 1
CCDYBIN = 1
EXPSTATE= 293
TEMPERAT= -1.186874500521e+001
INSTRUME= 'SBIG ST-10/10XE '
E-GAIN = +1.390000000000e+000
XPIXSZ = +6.800000000000e-003
YPIXSZ = +6.800000000000e-003
SBIGIMG = 8
EXPOSURE= +1.500000000000e+001
CBLACK = 13942
CWHITE = 15649
IMAGETYP= 'flat '../bias/zero.fits[2184,1472][real]:
No bad pixels, min=0., max=0. (old)
Line storage mode, physdim [2184,1472], length of user area 1215 s.u.
Created Wed 11:58:54 31-Oct-2007, Last modified Wed 11:58:50 31-Oct-2007
Pixel file "../bias/zero.fits" [ok]
EXTEND = F / File may contain extensions
ORIGIN = 'NOAO-IRAF FITS Image Kernel July 2003' / FITS file originator
DATE = '2007-10-31T03:58:54' / Date FITS file was generated
IRAF-TLM= '11:58:50 (31/10/2007)' / Time of last modification
BIAS = 100
TELESCOP= '400mm 100mm '
FOCALLEN= +4.000000000000e+002
APERTURE= +1.000000000000e+002
OBSERVER= 'Lelis1 '
DATE-OBS= '2007-02-05 '
TIME-OBS= '23:05:06 '
CCDSFPT = 2
CCDSUBFL= 0
CCDSUBFT= 0
CCDXBIN = 1
CCDYBIN = 1
EXPSTATE= 293
TEMPERAT= -9.787817267812e+000
INSTRUME= 'SBIG ST-10/10XE '
E-GAIN = +1.390000000000e+000
XPIXSZ = +6.800000000000e-003
YPIXSZ = +6.800000000000e-003
SBIGIMG = 8
EXPOSURE= +0.000000000000e+000
CBLACK = 90
CWHITE = 154
IMAGETYP= 'zero '
NCOMBINE= 10
EXPTIME = 0.
DARKTIME= 0.
Thansk!!
hymong

Dear Hymong,I suggest you create an "instrument translation file" for your data. This is described under the help topic "instruments":[code:1:253bf52cc7]
cl> phelp instruments
[/code:1:253bf52cc7]You would only need the following in the file:[code:1:253bf52cc7]
exptime exposure
darktime exposure
[/code:1:253bf52cc7]Put this file, you might call it sbig.dat, in your IRAF login directory. Then in the ccdred package parameters set[code:1:253bf52cc7]
instrument = home$sbig.dat
[/code:1:253bf52cc7]Now CCDPROC and other tasks will use the EXPOSURE keyword that is in your data.[quote:253bf52cc7]
It seems that the problem I encountered is something wrong about the keyword "EXPOSURE" and "EXPTIME" and its value. But if it is right, why it worked well when I subtracted combined zero from each dark image to get pure-dark one by doing the command:ccdred> ccdproc @d.list ccdtype=dark fixpix=no oversca=no trim=no zerocor=yes darkcor=no flatcor=no zero=../bias/zero.fits
[/quote:253bf52cc7]The reason this works is because the only time the exposure is needed is for dark subtraction. If you only did zero (same as bias) subtraction and flat fielding then you would not have to worry about the exposure time keyword.I hope this solves your problem.Yours,
Frank

Dear Frank,I am very sorry to try your suggestions now. This time I haven't encountered the previous error. Thanks for your kindly helps very much. Now I know that in my previous parameters setting of ccdred package, I didn't provide proper Instrument Translation File of my SBIG CCD Camera. So the default settings are not correct. Next time when I process another CCD Camera's images, I will pay much attentions to the related parts.Thanks for your warm and kindly helps VERY MUCH againHave a nice weekend!!
hymong