Charon and drift scan images taken by SCAN

Charon is a program written by Bill J. Gray see: Charon

To use Charon to examine drift scan images,
fill in the settings in Charon like this:

Report file name


Saturation point


Cutoff point


Focal len (inches)


Image offset


Pix width (microns)


Scale tolerance


Pix height(microns)


Search distance


Image is uninverted

Observer code


Match to GSC-ACT

Time offset


File date gives end of exposure

Maximum residual


Mag limit:


Number stars used



White stars on black

Object name:

GSC 1267 237

RA/dec in decimal seconds

Simple centroiding

Video mode:

320 x 200

Max tilt angle:

90.00 +/- 4.00

Linear (first-order) fit

Photometric band:

Centroid size


Save settings

Charon will calculate a correct mid exposure time.
( but only outside the ramping )
The time and date in the file info of an image taken by SCAN, will indicate the time, when the first line of the image is read out. Nevertheless/therefore in Charon it is necessary to set: File date gives end of exposure
In files sliced from JimsSilce or ViewScan the time in the file info is also the time, the first line (of the new file) is read out, same settings as mentioned before.
It is also important to set: Image is uninverted and :
Max tilt angle: 90.00 +/- 4.00
(Max tilt angle: 90.00 +/- 1.00 should also work)
(In images taken by SCAN West is at the top)
In large images,it should be set:
Maximum residual 2.0
Search distance 2 or 4 or more, depends on the size of the image

If Charon don't works with that settings, try to change some items
It may be easier to use smaller or sliced images
(I got Charon work with images up to 765 * 10000 pixels, but the settings in Charon have to be adjusted carefully)

In large images, it may help, to fill in the exact RA and DEC of the center of the image (at Object name).
Video mode: try different settings