Random Displacement (Rd) Screen - Lacerta M-Gen User Manual

5.1.3 Random Displacement (RD)
screen
About the meaning of RD see 4.3.
Below are the screen's items and detailed
descriptions:

Enable
: (switch) profile
To enable or disable the RD function.
If enabled, rigth after the currently running exposure (in AE) has ended this generates
a new guiding position for the guide star.

Uniform square
The used method to generate the positions. The two above can be set.

width
: (real, 0.01 ...99.99) profile
The width or size of the patterns. It is interpreted differently by the two modes.
Uniform square mode:
It means a quasi uniform distribution of points within a square. The pattern is
predefined and is designed to cover the whole area uniformly even at low number of
exposures.
The "width" stands for the width of the square's sides, the unit is pixels (in the
Camera). (Note: the physical pixels are not exactly square shaped so the Y coordinates
(size) are scaled to be equal to X, which is the horizontal axis.) For example width=16
means a [-8..8] pixel interval for each axis relative to the autoguiding center (where the
AG has been started).
Square snake mode:
This pattern is not random but the pattern shown at right. It steps
on a square grid, the step size is always the same. The first step is to
right (RA axis) and the next steps are counterclockwise around the
previously used positions.
In this mode "width" is interpreted as the grid distance or one
step's size. This has an other scale than the other mode, be careful and check the size
every time You change between the modes.
Each new guiding position coordinate is limited to 16 pixels close to the CCD surface's
border, to avoid star lose.
A new displacement is generated by the Autoexposure program when it goes into wait
state. In this case the AE waits until the new position has been stabilized and continues the
program after it (see the example at the end of section 5.1.1).
Square snake
or : (text) profile
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