Generated Fri, 14 Oct 2016 07:22:57 GMT by s_wx1131 (squid/3.5.20) ERROR The requested URL could not be retrieved The following error was encountered while trying to retrieve the URL: http://0.0.0.10/ Connection Next use imarith to divide the averaged flats by their mean values. The pixel mask file name comes from the image header keyword BPM. For example "grid 5 100 5 100" specifies a 5x5 grid with origins offset by 100 pixels.
See Changing Fits Headers in the CCD Reduction with ccdproc section. Voila! If you entered these filenames in the parameters section, they will be shown in parentheses. The computer will ask for an input file name. http://iraf.net/forum/viewtopic.php?showtopic=138430&lastpost=true
They are used in conjunction with the maskvalue parameter. Why the two methods? Often the sensitivity noise, due to uncertainties in the pixel sensitivities (for example from the flat field), is not known in which case a value of zero can be used. Type ls and you should be able to see the new image.
A record of what occured in ccdproc will be deposited in the folder where it occured. blank = 0. You will find yourself immediately in the editor for several of the parameter files needed for data reduction. Iraf Imstat Once you have the parameters editted, you can enter: darkcombine input output=output at the prompt.
This is the best clipping algorithm to use if the CCD noise parameters are adequately known. Imcombine Now you can enter flatcombine and IRAF will prompt you for input files. See the DESCRIPTION section for further details. http://astroweb.case.edu/lucy/MMTnov/iraf.html You will definitely need to use the scaling option if you are using screen or dome flats.
Open it in emacs by entering emacs login.cl & Look for the section, # Uncomment and edit to change the defaults. Ccdproc Iraf The pixels may be combined by computing the median or by computing a weighted average. shifts -- a text file, one line per input image, containing an estimate of the shifts between the images. You will have to edit the parameter listing for ccdproc in order to select the bias frame. (See Ccdproc) scale="none" The default will be set to scale by exposure time.
When the parameters are set properly, exit the editor using Esc :wq and then simply type zerocombine The computer will prompt you for your input file names. The mathematical representation of the basic reductions to correct additive and multiplicative errors is: final_image = (raw_image - dark1)
(flat - dark2) /
Combining Flats To combine flat images, use the task flatcombine. Say they're named bias01.imh, bias02.imh, etc. Or display the image on the screen to make sure the that Zero.imh looks smoother than any of the bias??.imh files. 3) Making a master Dark Frame (only at GCO) The If you want to keep your backup, be sure to enter an output filename. Iraf Zerocombine
If the images are scaled differently and the sigma scaling correction threshold is exceeded then a correction is made in the sigma calculations for these differences, again under the assumption that Please try the request again. grow = 0 Number of pixels to either side of a rejected pixel along image lines to also be rejected. Use rfits to make sure all your dark frames are in IRAF format.
plfile = "" (optional) Output pixel list file or list of files. Iraf Normalize Flat IRAF then reads all the flatfield images, subtracts Zero and Dark from each, averages together ones of the same filter, and prduces a master flat for each filter. GROW REJECTION Neighbors of pixels rejected by the rejection algorithms along image lines may also be rejected.
If left blank then the input datatype of highest precision is used. When the offsets are read by the program it will find the mininum value in each dimension and subtract it from all the other offsets in that dimension. If there is more than one pixel with the same absolute residual (for example the two pixels about an average or median of two will have the same residuals) they are Imhead Iraf The world coordinate at the center of the first input image is evaluated.
Can other tasks like IMSTAT or IMHEAD open the images properly? Thus the name you give as an output file name is a "root" name, to which the filter name will be added when the master flat is created. If the mask type selects good or bad bits the value may be specified using IRAF notation for decimal, octal, or hexidecimal; i.e 12, 14b, 0cx to select bits 3 and We could create a list file which contains the names of the output images and call them 70flat_V_ds.fits, 71flat_V_ds.fits, and 72flat_V_ds.fits, where ds stands for dark subtracted.
When all images are saved, extra pixels are added to the sides. combine="average" reject="minmax" ccdtype="none" This is very important Zerocombine will look for images with IMAGETYP=zero in the fits header. Note that it is possible to reject all pixels if the average is used and is sufficiently skewed by bad pixels such as cosmic rays. Post Reply Print view Search Advanced search 11 posts • Page 1 of 1 aaron Posts: 8 Joined: 2013-07-01T18:08:35-07:00 Authentication code: 6789 Just want to combine 2 images Quote Postby aaron
You can name the output zero file whatever you want, but make sure its the same name you set earlier in the ccdproc parameter file, or edit the ccdproc "zero level The parameters affecting this algorithm are reject to select this algorithm, pclip to select the percentile pixel, nkeep to limit the number of pixels rejected, and lsigma and hsigma to select It appears to be looking for the bias image Zero. When you open IRAF, you are located in your iraf directory.