Cluster Info for Abell 1413: 
PHYSICAL SCALE: our images of Abell 1413 scale as 
                   743 h^-1 pc/pixel
                   146 h^-1 kpc/arcmin
                
                the image a_1413.cut.fits is 1.37 x 1.27 Mpc



(the following cluster information was taken from the NASA/IPAC Extragalactic 
Database (NED) which is operated by the Jet Propulsion Laboratory, California 
Institute of Technology, under contract with the National Aeronautics and 
Space Administration. http://nedwww.ipac.caltech.edu/ )

Helio. radial velocity     :  42780     km/s    ;                                         
Redshift                   :  0.14270           ; 1999ApJS..125...35S                     
Magnitude/rank of member   : 17.1/10                                                      
Cluster Diameter (arcmin)  : 32                                                           
Morphology [System]        : I      [BM]                                                  
Pop. or  [Richness Class]  : [3]                                                          
                                                                                          
Galactic Extinction (Burstein & Heiles): A_B = 0.020 mag; 1982AJ.....87.1165B             
Galactic Extinction (Schlegel et al.):   A_B = 0.102 mag; 1998ApJ...500..525S             
 E(B-V) = 0.024 mag. The following values assume an R_V = 3.1 extinction curve.           
 See Cardelli et al. (1989ApJ...345..245C) for other conversion factors.                  
 Bandpass           U     B     V     R     I     J     H     K     L'                    
 Wavelength [um]  0.34  0.44  0.54  0.65  0.80  1.27  1.67  2.22  3.81                    
 A_lambda  [mag]  0.129 0.102 0.079 0.063 0.046 0.021 0.014 0.009 0.004                   
                                                                                          
                                                                                          
NOTES:                                                                                    
                                                                                          
1999MNRAS.306..857C                                                                       
Re:ABELL 1413                                                                             
A second, smaller galaxy also lies on the slit, at a separation of only                   
9.5 arcsec (31kpc) to the N. We present the spectrum only of the main                     
galaxy. Maurogordato et al. (1997) note the presence of a small                           
foreground group of galaxies at z=0.1.                                                    
                                                                                          
1997A&AS..123..411M                                                                       
Re:ABELL 1413                                                                             
A1413 shows a main concentration of 9 galaxies at a mean velocity of                      
v_BI_=42686 km s^-1^ (including the central cD galaxy) identified as the main             
cluster. The estimate of its velocity dispersion (listed in Table 2) is                   
S_SD_=1460 km s^-1^. This value is quite different from the estimate with the             
bi-weighted method (S_BI_=370 km s^-1^). This can mean that the number of                 
galaxies is still not sufficient to use the bi-weighted technique. Previous               
estimates of the velocity dispersion in A1413 have to be taken with care until            
more redshift measurements are available.                                                 
Finally, we note the presence of a foreground group of 4 galaxies around                  
v=30000 km s^-1^.

Cluster Info for MKW 7: 

PHYSICAL SCALE: our images of mkw 7 are scaled as
                    117 h^-1 pc/pixel
		    23 h^-1 kpc/arcmin
		the image mkw_7.cut.fits is 228 kpc x 209 kpc

(the following cluster information was taken from the NASA/IPAC Extragalactic 
Database (NED) which is operated by the Jet Propulsion Laboratory, California 
Institute of Technology, under contract with the National Aeronautics and 
Space Administration. http://nedwww.ipac.caltech.edu/ )

Helio. radial velocity     :     8694     km/s  ;
Redshift                   :  0.02900           ; 1992NED11.R......1N
Magnitude/rank of member   : 15.0/1     
Cluster Diameter (arcmin)  :      
Morphology [System]        :                        
Pop. or  [Richness Class]  : 22   
 
Galactic Extinction (Burstein & Heiles): A_B = 0.060 mag; 1982AJ.....87.1165B 
Galactic Extinction (Schlegel et al.):   A_B = 0.162 mag; 1998ApJ...500..525S
 E(B-V) = 0.037 mag. The following values assume an R_V = 3.1 extinction curve.
 See Cardelli et al. (1989ApJ...345..245C) for other conversion factors.
 Bandpass           U     B     V     R     I     J     H     K     L'
 Wavelength [um]  0.34  0.44  0.54  0.65  0.80  1.27  1.67  2.22  3.81
 A_lambda  [mag]  0.204 0.162 0.124 0.100 0.073 0.034 0.022 0.014 0.006

More on Bias Subtraction, trimming and Zero subtraction:
We followed the standard procedure for bias subtraction and overscan trimming: average the pixel counts over all the columns in the overscan region and fit these values as a function of line-number. Subtract this fit from each column in the image. After subtraction, trim off the overscan region.
This process was executed using IRAF's ccdproc, with parameters overscan, trim, and zerocor set to yes.
back

More on Zero Combination:
Using IRAF's zerocombine operation, we produced an averaged zero frame for each of the four obsering nights (Zeron1 -> Zeron4). To create each pixel in Zeron1, for example, zerocombine averaged the corresponding pixels in all of the night one zeros. The highest value in each pixel set was not included in the averaging (this helps to remove the effects of any cosmic rays on the zero frames). Another pass through ccdproc with the name of the appropriate zero frame entered in the zero parameter space completed the zero subtraction.
back

More on initial flat fielding:
The dark sky flats were combined using IRAf's flatcombine tool into two seperate flats, one for nights one and two, and another for nights three and four. These flats were used to flat-field all of the cluster images before the initial analysis stage and these flats were also used in the first iteration of the flat-creation script explained below.
back

More on the improved flat fielding:
The IRAF script we used to make our improved flats has a multitude of steps.
The first step is to flatten all the sky images with a preliminary flat, provided by the user.
Each of the flattened skys are then binned up to get rid of stars and cosmic rays and such.
The next step is to fit a plane to each of the flattened, binned-up skys. The planes are scaled to the mean sky, and the flattened skys (flattened but not binned) are deplaned and binned up (these flattened, deplaned, binned skies are used to find the mode of each sky, which imcombine uses when creating the final combined sky flat).
Now that the modes have been found, the program divides the raw images by the normalized planes.
Finally, the deplaned "raw" skies are combined (using imcombine) into the end product: a single dark sky flat to be used in flatfielding the cluster images. Along the way, the images are divided into half-splits.
The program ends by calculating the half-split sigma to allow for easy quality analysis of the end-product sky flat.
back

More on Preliminary image analysis:
The preliminary analysis of the data was primarily to get a feel for any systematic errors and to catalogue the quality of the skys and the cluster images. As we examined each of the images we noted any severe focus or seeing problems, the presence of any artificial brightness gradients in the image, any vignetting that the initial flat-fielding didn't correct, and anything else unusual. The most notable item that fit in this last category was the "rug of doom" which popped up in a considerable number of images from nights 3 and 4.
back

More on image combination:
Combining the cluster images was a six step process.
First, the raw images (images of the clusters that have only been bias subtracted, trimmed and zero-subtracted) were flat-fielded with the current best flat (from the flat-creation script). The second step was to find a sky value to subtract from each image. We examined each cluster and found two sections that were relatively free of bright galaxies and stars. Using IRAF's imcopy, we cut these sections out and made two small sub-images. We then ran each image through a program called spikemode, which calculates the mode of all the pixel counts in each image. With two modes for each image now, we averaged them to get a final value for our sky constant. We then subtracted the appropriate sky-value from each image.
Next, we found 10-12 reference stars in each cluster. The positions of these reference stars were recorded into files using IRAF's imexam tool.
The fourth step was to run these coordinate files through IRAF's geomap tool to produce a database file for IRAF's geotran tool. Geotran then does the brute work of shifting all of the images of a particular cluster so that the reference stars line up.
The fifth step was the actual combination of the images, using IRAF's imcombine tool.
The sixth and final step in the combination process was to sky-subtract the combined image in the same way as was done in step one. (This was intended to compensate for any small errors in the initial sky-subtraction, which would have been multiplied 10-fold in the combination process.)
back