Celestron Compustar Manual de instrucciones descargar pdf (Pagina 33)

guide camera chip and is lost. This takes some trial and error, but is best accomplished by

placing the calibration star in the center of the guiding chip so it has the capability of moving as

far as possible in both RA and Dec directions without leaving the chip. Within these constraints,

the time interval selected should be about the same as the longest time required to manually

correct the greatest periodic error that the RA drive makes. This can be determined by practicing

some manual guiding and timing the corrections. The reason for this is that the Compustar motor

drives accelerate during the time that the motion keys are depressed. Thus, if the software

commands the drive to move much longer than will actually be needed during autoguiding, the

calibrated speeds derived may be faster than those actually required for small corrections. This

can result in over correction. Once you know the time intervals that work for calibration of each

axis, you can use those times for almost all future calibrations. Another important point is that

the orientation of the guiding camera during calibration should be absolutely identical to that

used during the imaging session. Otherwise, the software will make guiding corrections in the

wrong directions.

If your guide star is fairly bright, you can set up the imaging session and then perform calibration

using that guide star before you begin autoguiding. However, particularly with off-axis guiders,

the best available guide star may be too faint to obtain a good calibration. You may repeatedly

get some type of “Calibration failed” message. That does not mean you cannot use it as a guide

star. All that is lacking is a good calibration, which can be obtained with a brighter star

elsewhere in the sky. If you are imaging one of the objects in the Messier or CNGC catalogs,

then once you have the image set up with the guide star acquired on the guiding chip at the same

time that your subject is framed acceptably in the imaging camera, an important trick you can

use is to simply push the “SYNC” key. Do this even though the object itself is no longer in the

exact center of the field of view. This will have the effect of locking the current position of the

center of your astrophotograph composition into the Compustar computer as being the

coordinates of the subject itself. You can then manually slew, using the motion control keys (or

joystick), to a fairly bright star somewhere nearby in the sky and use it obtain an accurate

calibration. You should not rely on commanding the Compustar to slew to the coordinates of that

brighter star or even to a nearby Reference Star because the Compustar is now out of “SYNC”

with the entire sky. It is best to use your finderscope for acquiring the brighter star. Start by

centering the star on your imaging camera‟s chip. You then have to be able to shift the position

of the star onto your guide camera‟s chip, which takes a bit of skill with an off-axis guider.

However, if you know where your guiding chip is relative to the imaging chip, you can

maneuver the guide star onto the guiding chip in a series of small steps using the motion control

keys and “SET” speed.

Once the star is acquired and centered on the guiding chip, perform the calibration routine. Then

simply command the Compustar to “SLEW” back to the Messier or CNGC object. Because you

hit “SYNC” before you moved the telescope, the Compustar should faithfully slew back to the

position of your previous composition, with the guide star on the guide chip and the image

1 2 ... 28 29 30 31 32 33 34 35 36 37 38 ... 47 48

Sin comentarios

Celestron Compustar Manual de instrucciones Pagina 33