GUIDER INSTRUCTIONS
In normal automatic use, if the Guide row in the
Picture table
of the database is set then the photo
procedure will do the following steps automatically.
If not, first open the observatory (and keep the dome open)
and point the telescope to the desired coordinates
and follow the next steps.
SELECTING A GUIDESTAR AND POSITIONING THE STAGE
The guidestar program
looks at the present telescope coordinates and creates a list
of stars in a two degree neighborhood using the
bright command invoked with
the tycho option.
This star list is then fed through the setstage
program which determines the x, y coordinates of the stars and the amount
of vignetting by the guider.
This list is then sorted to find the brightest unvignetted star that
does not block the science chip.
If no star is found, the script exits with a non-zero code.
Finally the stage is positioned to to the proper position.
ACQUIRING THE GUIDESTAR
With the stage properly positioned, the
acquire script is run.
This script does the following:
- takes an image using the guide camera with
guimage
- subtracts off a dark (generating one if necessary)
- looks for stars using XVista stars
- finds the brightest one
- moves the telescope to center the star
GUIDING
Once the guide star is acquired, the
guide script keeps
the telescope centered.
The script does the following:
- takes a picture using guimage
- subtracts off a dark
- determines the centroid within a small box in the center using the
XVista centroid command
- offsets the telescope as needed
- repeats
Instructions Index