Instructions for FITSVector 021306
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FITSVector starts up showing a window similar to
FITSRegister which can hold 2 FITS images, either planet
images or lat/long maps.  To load images, either type in the
path name in the File1 and File2 fields and press 'enter' or
'Load', or press 'Browse' to bring up an open dialog.  You
can only load files with the extension '.fits' from the
browsing dialog, but you can load any FITS file from the
path field. Only FITS files with a single 2d image (primary
HDU) can be loaded.

Usually, either two planet images previous aligned and saved
by FITSRegister, or two lat/long maps produced from aligned
planet images, are loaded into the File1 and File2 slots. 
Scales can be set independently for each image, but the zoom
is shared by both images. The controls at the upper right of
the window determine which file is currently displayed.
Headers for the two files can be displayed from the 'Window'
menu.

A table showing the currently defined vectors can be shown
from the 'Window' menu.  Vector tails are in the x0 and y0
columns, tips are in the x1 and y1 columns, and the dx and
dy columns are computed from the tails and tips.  Create new
vectors by clicking the mouse in the images.  Clicking in
the File1 image creates a new vector tail, which is shown in
the table and overlaying the File1 image.  Create as many
vector tails as you want by continuing to click in the File1
image. As you click and then move the mouse, the current
coordinates (x, y, image value) are displayed in the
'Coords' field.

Switch to the File2 image display (with radio buttons or
'Swap') to create vector tips corresponding to currently
existing vector tails. Click in the File2 image to add a new
vector tip to the next vacant columns in the vector table. 
Both the tails and tips are numbered in the displays, and
vector tips are created sequentially to correspond to
existing vector tails.  If you try to create a vector tip
for which there is no tail, you will get an error message.

Note that you can create vectors in a single window,
swapping between the File1 and File2 displays, or in
multiple windows, each showing either File1 or File2
(although all corresponding slots should be loaded with the
same images).  As you create vectors in one window, all
corresponding displays in other windows will be updated
simultaneously.  Also note that reloading any File1 will
delete all vectors, while reloading any File2 will delete
all vector tips only.

If you set the zoom to a value > 1x, creation of vector
tails and tips will be in fractional pixel coordinates, with
the resolutiuon = 1 / zoom.

You can edit a vector in the table by double clicking in one
of the x0, y0, x1, or y1 cells of the table.  Type in the
new value you want and press 'return' or 'enter'.  The
vector tail or tip will be moved and redisplayed in all
images, and the new dx and dy values displayed in the table.
You can set vector tails and tips to any fractional value
by editing the table, regardless of the current zoom
setting. To delete a vector, select the row in the table by
single-clicking, and then press either of the 'delete' keys
(one is on the keypad).  The selected vector will be removed
from all displays.

To show vectors as arrows, click the 'Plot->Arrows' radio
button at the upper right of the window. Note that arrows
will appear only for those vectors which contain both a tail
and a tip.  You can set a scale factor which is applied to
the length of the vector when it is drawn, and you can click
a checkbox which determines whether the current zoom factor
is also applied to the vector length.  Vector numbers can be
optionally displayed beside arrows or not (numbers are
always displayed beside tails and tips alone).

You can save the current vectors in the table to a text file
by choosing 'File->Write Vectors...'.  You can then edit
this file with a text editor such as BBEdit.  Note that this
file must be maintained in Unix format, which uses a newline
('\n' character) at the end of each line.  This is how the
file is created by FITSVector, and there is an option in the
BBEdit save dialog to determine this as well.

You can load a table of vectors from a text file by choosing
'File->Read Vectors...'.  This file must be in Unix format
(see above).  The first line of the file contains the number
of vector tails and tips, and then each additional line
contains the values for x0, y0, x1, y1, dx, and dy
(delimited only by spaces).  Note that dx and dy are
superfluous in the file, as they are recalculated from the
tails and tips when the file is read.

That's it so far.  Note that the vector lengths are in raw
pixels, and have no intrinsic relationship to planetary
distances.  Also note that the vector lengths (and possibly
angles) may not be isomorphic due to the lat/long projection
created externally.

Please test these features and send comments to
skycoyote@comcast.net.