Celestron 8i User Manual
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Even though the NexStar can precisely track a celestial object while in the Alt-Az position, it is still necessary
to align the polar axis of the telescope (the fork arm) to the Earth's axis of rotation in order to do long
exposure astro photography. To do an accurate polar alignment, the NexStar requires an optional equatorial
wedge between the telescope and a tripod. This allows the telescope's tracking motors to rotate the
telescope around the celestial pole, the same way as the stars. Without the equatorial wedge, you would
notice the stars in the eyepiece would slowly rotate around the center of the field of view. Although this
gradual rotation would go unnoticed when viewing with an eyepiece, it would be very noticeable on film.
to align the polar axis of the telescope (the fork arm) to the Earth's axis of rotation in order to do long
exposure astro photography. To do an accurate polar alignment, the NexStar requires an optional equatorial
wedge between the telescope and a tripod. This allows the telescope's tracking motors to rotate the
telescope around the celestial pole, the same way as the stars. Without the equatorial wedge, you would
notice the stars in the eyepiece would slowly rotate around the center of the field of view. Although this
gradual rotation would go unnoticed when viewing with an eyepiece, it would be very noticeable on film.
Polar alignment is the process by which the telescope's axis of rotation (called the polar axis) is aligned
(made parallel) with the Earth's axis of rotation. Once aligned, a telescope with a clock drive will track the
stars as they move across the sky. The result is that objects observed through the telescope appear
stationary (i.e., they will not drift out of the field of view). If not using the clock drive, all objects in the sky
(day or night) will slowly drift out of the field. This motion is caused by the Earth's rotation.
(made parallel) with the Earth's axis of rotation. Once aligned, a telescope with a clock drive will track the
stars as they move across the sky. The result is that objects observed through the telescope appear
stationary (i.e., they will not drift out of the field of view). If not using the clock drive, all objects in the sky
(day or night) will slowly drift out of the field. This motion is caused by the Earth's rotation.
Wedge Align
Using the computerized hand control, the NexStar has two equatorial wedge alignment modes (one for the
northern hemisphere and one for the southern) that will help you polar align your telescope. After performing
either an EQ AutoAlign or Two-Star Alignment, Wedge Align will slew the telescope to where Polaris should
be. By using the tripod and wedge to center Polaris in the eyepiece, the fork arm (polar axis) will then be
pointing towards the actual North Celestial Pole. Once Wedge Align is complete, you must re-align your
telescope using either the EQ Two-Star or EQ AutoAlign methods. Follow these steps to Wedge Align the
NexStar in the Northern Hemisphere:
northern hemisphere and one for the southern) that will help you polar align your telescope. After performing
either an EQ AutoAlign or Two-Star Alignment, Wedge Align will slew the telescope to where Polaris should
be. By using the tripod and wedge to center Polaris in the eyepiece, the fork arm (polar axis) will then be
pointing towards the actual North Celestial Pole. Once Wedge Align is complete, you must re-align your
telescope using either the EQ Two-Star or EQ AutoAlign methods. Follow these steps to Wedge Align the
NexStar in the Northern Hemisphere:
1. With the telescope set up on an optional equatorial wedge and roughly positioned towards Polaris,
align the NexStar using either the EQ AutoAlign or Two-Star Alignment method.
2. Select
Wedge Align from the Utilities menu and press Enter.
3. Based on your current alignment, the NexStar will slew to where it thinks Polaris should be. Use
the tripod and wedge adjustments to place Polaris in the center of the eyepiece. Do not use the
direction buttons to position Polaris. Once Polaris is centered in the eyepiece press ENTER; the
polar axis should then be pointed towards the North Celestial Pole.
direction buttons to position Polaris. Once Polaris is centered in the eyepiece press ENTER; the
polar axis should then be pointed towards the North Celestial Pole.