NAME
skyflat
SYNOPSIS
skyflat tarid= logid= [optimum=]
DESCRIPTION
This procedure does the special things needed to
create a sky flat field image.
- runs openup
- If at dusk, it points telescope 10 degrees east of zenith
- If at dawn, it points telescope 10 degrees west of zenith
- Turns off telescope tracking and lights
- For each PictureID it takes an image
- Uses Picture.ExposureTime,Picture.Binning, and Picture.FilterID
- Subtracts bias frame
- Determines mean value and adjusts exposure with brightness fudge
- Repeats Picture.Count time jogging telescope a degree or so
- Writes FITS file with detailed header
canonical name
- Sets IMAGETYP to 'FLAT'
The program attempts to adjusts the exposure time so that
the mean signal level (above bias) is OPTIMUM.
The value of OPTIMUM can be optionally set on the command line
or the default viewed in the code below.
If the exposure is too short, the program sleeps SLEEPTIME.
If the exposure is too long, the program exits.
See the source code for the definitions of MAXTIME,MINTIME,
OPTIMUM and SLEEPTIME.
A fudge factor is added to compensate for the darkening at
sunset or brightening at dawn.
The pictures are taken in order of increasing exposure time
so if you want to take pictures in a different order,
adjust the exposure times as they are just straw men.
The XVista routines of sub and
mn are used to perform image
arithmetic.
Program Index