Hi Eric,

The file 'ccds.nam' (should be in your Guide folder) has all
the data on CCD sizes and placement. It starts out with 180 or
so lines, one for each camera. But after that, it has some
text explaining how the camera positions are stored... which
I'll just cut-and-paste below.

I'll emphasize that the "new" method of describing guider
chip offsets, where you give the guider chip pixel size in
microns and its offset from the main chip in millimeters, is
_greatly_ to be preferred. I've no idea what my younger self
was thinking when I specified those dimensions in units of
the height and width of the imaging chip.

-- Bill

------------- text from 'ccds.nam' ----------------

Certain SBIG cameras include guider chip specifications following the
ID number. The placement, size, and pixel dimensions of the guider
chip are given for each camera.

Some of the guider chip placements are done in a "legacy" manner,
in which the offsets and guider chip sizes are given in units of the
size of the main chip. That was somewhat stupid of me. In adding
new chips, I recommend use of a new scheme, described below in
relation to the MegaTek and SBIG 11000XM chips (the first two for
which the "new" scheme was used.)

In both the "new" and "legacy" systems, the main imaging chip is
specified in the normal manner: a camera name, chip part number,
pixel width/height in microns, number of pixels, and a unique
identifying number. That part is completely unchanged.

The guider chip data is on the same line, following the main
chip data, and is described by six numbers. In the 'legacy' system,
those will look something like this :

-.5,.6,.25,.19,192,165

In this example, (-.5,.6) = offset between the centers of the guider
and main chip, with the size units being the width and height of the main
chip. Thus, if the first two numbers had been (.5,.5), we'd be telling
Guide that the center of the guider chip is exactly on the upper right
corner of the main chip. (0,-.7) would mean the guider chip was a little
below the center bottom of the main chip. And so on... as it is, the
(-.5,.6) means that the chip is just a little above the upper left corner
of the main chip. (For all current SBIG cameras, the x-offset is zero,
because the guiding chip is straight above the main chip.)

(.25,.19) means the guider chip has 25% of the width, and 19% of
the height, of the main chip. This places the lower right of the guider
chip almost, but not quite, on top of the upper left of the main chip:

,-----,
| | <- Guider chip
|_____|
,-----------------,
| |
| |
| Main chip |
| |
| |
'-----------------'

(192,165) means that the guider chip is 192 by 165 pixels (which,
in fact, is the size of the TC-211 chip used as a guiding chip for
many SBIG cameras). You can omit this if you wish; the only place it
is used is in showing the grid of pixels. Omit these numbers, and the
only consequence is that Guide can't show you the pixel grid on the
guider chip.

As mentioned, the MegaTek, SBIG 11000 XM, and probably any
cameras to be added in the future use a different system. For these,
the guider chip data starts with an 'm' (for 'metric'), indicating
that the offsets are in millimeters, followed by pixel sizes in
microns, then the width and height of the guider chip in pixels.
For the Megatek, for example,

m0,30.481,9,9,352,288;0,-30.481

the center of the guider chip is 30.481 millimeters from the
center of the main chip. The guider chip has an arry of 352x288
pixels, each 9 microns square. The MegaTek is unusual in that
it has _two_ guiding chips, symmetrically placed around the main
chip; this allows it to account for field rotation. The data
for the second chip follows that for the first. The only data
given for it is its position; the sizes are the same as for the
first chip, so we can leave them out.

On 2017-12-29 11:23, eric@... [guide-user] wrote:
>
>
> How do I adjust the position of the guide chip frame on the visualization? We have made some changes in the setup of our SBIG camera and had to change the position of the pickoff prism. The new position is a bit further out from the main sensor.
>
> Instructions would be appreciated. Thanks.
>
> Eric