III
C
one Error Calibration
"Cone" error is a common inaccuracy found on all German equatorial mount. It is a result from the
optical axis not being aligned to the R.A. axis of the mount. This affects the pointing accuracy of
the EQ6 SkyScan
TM
. Three-Star Alignment automatically compensates for the "Cone" error. If you
choose One-Star or Two-Star Alignment method, you will need to perform manual mount
calibration to eliminate the "cone" error. The following calibration procedure should be performed
before the initial use of the telescope and periodically thereafter to ensure the accuracy.
Testing for Cone Error
This test is done at night using two bright stars located on the opposite side of the sky. Make sure
the telescope is properly polar-aligned using the polarscope. Perform the One-star Alignment
using an eastern star as the alignment star (see p.12 for details on the One-star Alignment). After
the star alignment, choose a bright star on the western sky from the SkyScan
TM
object database
and have the telescope slew to the star. If the optical axis is perfectly aligned to the R.A. axis, the
telescope will accurately put the star in the center of the eyepiece. In this case, there is no "cone"
error in your telescope setup and you will not need to perform the calibration. It is acceptable if the
star is slightly off-center as long as it is in the eyepeiece view and close to the center. Many factors
determine the pointing accuracy of the SkyScan
TM,
, for example incorrect star alignment, R.A. or
Dec lock knob being lose, or "cone" error. If your telescope puts the star outside the eyepiece view,
you need to first determine whether it is "cone" error that causes the pointing inaccuracy. To find
out, simply move the telescope in R.A. axis by pressing the Left or Right direction key. If the star
can be moved into the eyepiece view without adjusting the Dec axis, it is likely that "cone" error
exists in your telescope setup.
Insert the illuminated reticle eyepiece.
Make sure that the telescope is properly
set up and balanced, and the
finderscope is perfectly aligned with the
telescope tube.
Calibration Procedure
Required accessory: Illuminated
reticle eyepiece with double
crossline pattern. Depending on the
design of your mounting plate
(dovetail bar), modifications may
be required. (See step 10 for the
required mechanism on the
mounting plate.)
Step 2 to 4 is to identify R.A. and Dec
movements in the reticle eyepiece. If
you are already familiar with the
movements, you may skip to step 5.
1.
2.
3.
4.
Find any bright star and place it in the center of the
eyepiece view.
Look into the eyepiece. Move the telescope in R.A.
axis using the R.A. direction keys on the hand
control while carefully observing the movement of
the star.
Keep moving the the telescope in R.A. axis back
and forth to keep the star within the eyepiece view.
Rotate the eyepiece until the movement of the star
becomes parallel to (or matches) any set of the lines
(Fig.v). This set of lines will represent R.A.
movement in the course of this procedure, and the
perpendicular lines will represent Dec movement.
Tigthen the set screws to secure the eyepiece in
place. Make sure that the eyepiece will remain
stationary when the telescope is being rotated .
rotate eyepiece
this way
eyepiece view
movement
of the star
Fig.v
Содержание EQ6
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