Ed_BPC users guide                   atp@uk.ac.ucl.mssl           jan 93

 ED_BPC exists mainly to facilitate easy changes to the preliminary
results file produced by BSDCAL, which is used by BSDFIT.  These include
such operations as filling in missed spectra, and forcing two velocity
components to be fitted. 
 

Contents:

	1) Method of Operation
	2) Command list and syntax
	3) Common problems
	4) Note.


 1) Method of Operation. 

   Once ED_BPC has been fired up from IDL it will ask for a bpc file to
read.  You are prompted to enter a filename or a wildcard, in which case
you will be presented with a list that meet the specified wildcard. 
   When the file has been loaded you are presented with the status line
and the ED_BPC prompt `` : ''.  At this point you can enter any of the
commands listed below.  By default the channel pointer is set to `3' -
for CaXIX, and the spectrum pointer to `0'.  The status line indicates
the current channel (c-3 for CaXIX) and the current spectrum ( s - <number>)
 and the time of this spectrum. 
   The initial default range wildcard is `*'.
   Once a command has been issued that affects the active range of
spectra (e.g.  f, d) then that range of spectra remains in force for all
subsequent commands.  Use the `s' command to reset the active range. 
 
 2) Command List.

  Enter ? to get an incomplete list of the following. 
   Case of the command is unimportant
    <range> is a string of type 
   '1,2,3' or '1,2,3-6' or '*'
    
   q                      =  Quit

    Quits ED_BPC.  If you have changed the BPC structure you are
prompted to save the file before exiting. 
   
  h	          = Help 

    Prints out the current BPC structure 

  ?                      =  Info
 
    Prints out a few lines with *some* of the commands.

   f   <range>     =  Fill Range

     This command takes the requested set of spectra (usually `*') and
attempts to fill in any gaps by substituting the nearest neighbour in
either direction.  Time fields are entered based on the assumption that
the SDGI of the donor spectrum is the same as that of the recipient
spectrum.  This means that filled spectra in the middle of an observing
program that changes the time resolution may well have incorrect times. 
Intensity, width position fields are NOT interpolated.  If you are
missing many spectra in a situation where the spectra are changing
rapidly, then you will have to check the results manually and/or rerun
BSDCAL with a less optimistic set of parameters. 
    
   d <range>     = Delete Range

   This command will delete spectra from the BPC structure.  If you have
spectra with really bad first guesses, then it may be an idea to delete
them and fill in from the neighbours. 

   ! <command>  = Shell escape 

    Pass command to IDL for execution.  See the execute() command in the
IDL manual for a list of do's and don'ts.  This is particuarly useful
for changing BPC structure items that are not addressed by specific
commands, as well as setting plot devices, issuing pprint commands,
etc... 

  s 	          = Set variables

    This is useful for resetting the active range of spectra to a
specific string.  You are presented with a number of options.  Type a
number then enter the requested item.  Error checking is non-existent. 
                 
  gc <chan>        =  Goto Channel

   This changes the active channel to <chan>. 
  1= FeXXVI, 2 = FeXXV, 3 = CaXIX, 4 = SXV

   gs <spectrum> = Goto Spectrum
 
  This changes the active channel to <spectrum>
  For this program the spectra begin with spectrum 1.

   w 		= Write 

   Write out your changes to a new BPC file.  By default the file
written is the has the same name as the original, unless you changed the
filename using the `s' command.  This probably will overwrite on Unix
systems. 

    e		= Examine

    Examine the contents of some parts of the struct of the current BPC
entry.  Items listed are
  1) The result of help,/struct for the current channel/spectrum
  2) The Background parameters.
  3)  Intensity, Width and Position of the `rest' or main
        component.

    r <range>	= Rest position line set

   This option sets the position of the `rest' component to some
explicit value for <range> spectra.  An example sequence of actions here
is to look at the position of this component with time using the `p pos'
command, select a spectrum that seems sufficiently settled, and the
examine the position of the rest component using the `e' command, for
that spectrum.  The rest of the spectra can then be forced to have this
value too by issuing a `r * ' command. 

     p (pos|int|wid)	= Plot 

   The three commands `p pos', `p int' and `p wid' all plot to the
current graphics device the specified item for the `rest' component.  `p
int' will give an approximation to the light curve.  `p pos' will plot
the position of the rest component with time.  As BSDCAL estimates the
position of this component by taking the peak of the combined profile as
the centre, then this position can migrate to the blue during the
initial phase of impulsive flares.  `p wid' is quite useful for picking
up on data quality vis a vis the line narrowing problem.  It is usually
pretty obvious from this plot when to stop taking the data seriously. 
The next release of this may overplot the point spread function as a
guide to help you. 

    b <range>	= Background

   This option forces the background to specific values for the
requested spectra.  The first component is the constant part, the second
the linear gradient. 

    2 <range>	= Force Two Component fit

   This is 90 percent of the reason for ED_BPC.  This command takes the
selected range of spectra, in a similar manner to the `f' command, and
attempts to supply a reasonable guess for the second velocity component
parameters, based on the nearest neighbour, and interpolation.  If you
have missing spectra, then fill them in before applying the second
component correction.  The guessed velocity is copied from the nearest
neighbour without change but the intensity will be scaled to match the
recipient spectrum. 

    reset		= Undo all changes

  This command will reset to the state read from the file. 
  It wipes out all changes.

    <cr>		= Advance by one spectrum

    This command will advance onto the next spectrum within the channel. 
 
3)  Common problems

  qu) It won't fill spectrum <n>
   a) Try including some spectra that exist in the range specification. 
`f *' is a good bet.  That goes for the `2' command too. 

  qu) It only plots a subset of the spectra
   a) Reset the active range using the `s' command.

  qu) It won't write out the file.
   a) This is an intermittent problem with wr_bsd.pro. 
   
  qu) I have forced a second component to all the spectra with ed_bpc,
 but the results from BSDFIT still indicate that only one component is
 being fitted. 
   a) These are first guesses.  BSDFIT reserves the right to ignore
 the second component if the fitting appears to demand this.  
 See af@uk.ac.ucl.mssl for details. 
     
4) note:
    
     This program was written by me for my own use. It was not Intended 
 to be user friendly, or have copious documentation. Use at your own risk.
 If you discover an error, then I will be grateful if you tell me of it,
 but this does not constitute a support policy.