Celestron Compustar Manual de Instruções descarregar pdf (Página 32)

relay box click as they flip from their “nc” to their “no” positions when the autoguiding

computer commands the mount to move in any direction. You will also hear the relays click back

to their “nc” positions when the commands have finished. These clicking sounds let you know

the relay box circuits are working.

The software then has all the information it needs to calculate how many pixels the mount moves

per second in each direction along each axis. This calibrates the autoguiding software so it knows

how long a movement it must command via the relays to correct a guiding error of any given

magnitude. The software may display a graphical representation of the movements of the guide

star during the calibration process and/or a table of the X, Y coordinates of the guide star on the

guiding chip after each calibration movement (Figure 18). The results may look like a cross.

However, the orientation of the cross with respect to true RA and Dec axes will depend upon the

orientation of the guiding camera with respect to those axes. The X and Y axes would be

completely reversed if the camera is rotated 90 degrees. For other software, the resulting graph

may resemble an “L”.

Figure 18. Graphical and tabular results of an autoguiding calibration run. The table at the

top shows the coordinates of the initial guide star position on the guiding chip and the

coordinates of its position after activation of each of the 4 relays, +X,-X,+Y, and –Y. The

graph shows the movement, in pixels, of the star on the chip. The orientation of the

resulting cross shows that the guiding camera chip’s axes were nearly perfectly aligned

with the axes of the mount, being only about 3 degrees off. It is important that the

orientation of the guiding camera during calibration be identical to that used for the

imaging session.

There are some important issues that will aid in good calibration. One is selecting the correct

time interval for the calibration movements in each axis. If the guide star does not move by a

minimum amount (often 5 pixels), you will get an error message. However, you have to be

careful that you don‟t select an interval so long that the guide star moves completely off the

1 2 ... 27 28 29 30 31 32 33 34 35 36 37 ... 47 48

Sem comentários

Celestron Compustar Manual de Instruções Página 32