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#883 Deluxe Field Tripod: Manufactured of strong, lightweight extruded
aluminum, the #883 Deluxe Field Tripod (Fig. 28) allows standing or seated
observations through the ETX-90EC. Tripod height is continuously adjustable
from 34" to 54". Micrometric controls in both azimuth and elevation-angle permit
precise polar alignment of the telescope's fork mount for astronomical
applications. Designed exclusively for ETX-series astronomical telescopes, the
#883 Deluxe Field Tripod includes all the rigidity and stability required for high-
power observing through the telescope. For terrestrial observing, where
altazimuth orientation of the telescope is desirable, the tripod head tilts and
locks at 90° (inset, Fig 28).
#882 Standard Field Tripod: (not shown) If the ETX-90EC is used primarily for
terrestrial observing and less-extensively for astronomical viewing, the polar
alignment capability of the #883 Deluxe Field Tripod may not be required. In this
case the #882 Standard Field Tripod provides a rigid observing platform for the
telescope in the altazimuth (Alt/Az) configuration, only. Alternately, if the
telescope is equipped with the optional #497 ETX Autostar Computer Controller,
astronomical sidereal-rate tracking can be effected in the Alt/Az configuration
permitted with the #882 Standard Field Tripod, without any requirement for polar alignment. The #882 Standard
Field Tripod is variable in height between 34" and 54" for seated or standing observing through the telescope.
Fig. 29: The #932 45° Erecting Prism threaded to the
rear cell of the ETX-90EC. (1) #932 45° Erecting
Prism; (2) Eyepiece; (3) Knurled Lock-ring; (4) Flip-
Mirror Control.
eyepiece-holder (as shown in Fig. 1), with the flip-mirror control in the "up" position. This admonition applies only to
situations requiring extraordinarily high optical resolution and where the observer's eye is well-trained to observe
very fine detail. In typical terrestrial applications, no image differences between the two eyepiece locations can
generally be noted.
#765 Soft Carrying Bag: Perfectly suited to field use of, or traveling with, the
telescope, the soft-padded, Cordura-type #765 Soft Carrying Bag (Fig. 30) for
the ETX-90EC includes a shoulder strap and permits ready transport of the
complete telescope, including the table tripod, eyepieces, and other
accessories. With the #765 Soft Carrying Bag the telescope can go anywhere
with you at a moment's notice.
#932 45° Erecting Prism: If the ETX-90EC is to be used for extensive
terrestrial applications, the #932 45° Erecting Prism (1, Fig. 29) is a
useful accessory. Images through the 90° eyepiece-holder (4, Fig. 1)
appear right-side-up, but reversed left-for-right. The #932 Prism threads
on to the telescope's photo port (17, Fig. 1) and presents a correctly
oriented image as well as a convenient 45° observing angle. An eyepiece
of any focal length (magnifying power) may be inserted into the #932
Prism. Note that the flip-mirror control (4, Fig. 29) must be in the "down"
position for use with the #932 Prism.
Important Note: In the most discriminating applications, such as in
observing delicate bird feather-structure at long distance, the ETX-90EC's
internal, optically-flat mirror yields a higher-resolution image than is
possible with any prism, including the #932. In these special cases ETX-
90EC users are advised to observe with the eyepiece in the standard 90°
Fig. 28: The #883 Deluxe Field Tripod with
ETX-90EC Telescope, set up in the Alt/Az
configuration (tripod head locked at 90°), for
terrestrial applications. (Inset) Tripod head
tilted for polar alignment.
Fig. 30: The #765 Soft Carrying Bag.
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