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5. Setting Circles
Setting circles included with the LX10 permit the location of
faint celestial objects not easily found by direct visual
observation. Located on the top surface of the telescope's drive
base, the R.A. circle (9, Fig. 1) is 8" in diameter. Declination
circles (8, Fig. 1) are located at the top of each fork tine. With
the telescope pointed at the North Celestial Pole, the Dec circle
should read 90° (understood to mean +90°). Objects located
below the 0-0 line of the Dec circle carry minus Declination
coordinates. Each division of the Dec circle represents a 1°
increment. The R.A. circle runs from 0
24
hr
, and reads in increments of 5
Note that the R.A. circle is double-indexed (i.e., there are two
series of numbers running in opposite directions around the
circumference of the R.A. circle). The outer series of numbers
(increasing counterclockwise) applies to observers located in
the Earth's Northern Hemisphere; the inner series of numbers
(increasing clockwise) applies to observers located in the
Earth's Southern Hemisphere.
To use the setting circles to locate an object not easily found by
direct visual observation: With the telescope aligned to the
pole, center an object of known R.A. in the telescopic field.
Then turn the R.A. circle, which can be rotated manually, until
the R.A. coordinate of the object is correctly indicated by the
R.A. pointer. As long as the telescope's motor drive remains
"ON," the R.A.pointer will then correctly indicate the R.A.of any
object at which the telescope is pointed throughout the duration
of the observing session.
To locate a particular object, first look up the celestial
coordinates (R.A. and Dec.) of the object in a star atlas. Then
loosen the R.A. lock and turn the telescope to read the correct
R.A. of the desired object; lock the R.A. lock onto the object.
Next, turn the telescope in Declination to read the correct
Declination of the object. If the procedure has been followed
carefully, and if the telescope was well-aligned with the pole,
the desired object should now be in the telescopic field of a low-
power eyepiece.
If you do not immediately see the object you are seeking, try
searching the adjacent sky area, using the R.A. and Dec. slow-
motion controls to scan the surrounding region. Keep in mind
that, with the 25mm eyepiece, the field of view of the LX10 is
about 0.5°. Because of its much wider field, the viewfinder may
be of significant assistance in locating and centering objects,
after the setting circles have been used to locate the
approximate position of the object.
Pinpoint application of the setting circles requires that the tele-
scope be precisely aligned with the pole (see Precise Polar
Alignment, page 12).
The setting circles may also be utilized in the absence of a
power source for the motor drive. In this case, however, it is
necessary to manually reset to the R.A. of the object you are
observing just before going to the next object.
6. Observing Tips
To enjoy your LX10 to the fullest, follow these recommen-
dations:
•
Always let the telescope "cool down" to the outside
temperature before attempting to make serious observa-
tions. After moving the telescope from a warm house, the
telescope's optics need about 15 to 20 minutes to adjust
to the outside temperature before they will perform well.
•
Avoid setting up the telescope inside a room and
observing through an open window (or worse, a closed
window!). In such a case air currents caused by
differences in indoor/outdoor temperatures make quality
astronomical optical performance impossible.
Note: A practical exception to this rule is the case where your
telescope is set up in a living room or den for observing an
- 14 -
hr
to (but not including)
min
.
outdoor terrestrial scene or view through a closed window. At
low powers (up to about 60X) the telescope will perform
reasonably well in this application, but the observer should
understand that the optical performance under these conditions
cannot approach the performance that will be realized if the
telescope were instead set up outside .
•
As discussed in Magnification (page 9), avoid "over-
powering" your telescope. If the astronomical or terrestrial
image becomes fuzzy at high powers, drop down to a
lower power. Image degradation at high powers is not due
to any fault of the telescope but is caused by heat waves
and turbulence in the Earth's atmosphere. Astronomical
observations at high powers (above 200X) should be
undertaken only when the atmosphere is very steady, as
confirmed by an absence of "twinkling" in star images.
•
Try not to touch the eyepiece when observing through the
telescope. Vibrations in your hand are immediately
transferred to the telescopic image.
•
If you wear eyeglasses and do not suffer from
astigmatism, take your glasses off when using the
telescope; the telescope's magnification compensates for
near- or far-sightedness. Observers with astigmatism
should, however, wear their glasses, since the telescope
cannot compensate for this eye defect.
•
Allow your eyes to become "dark adapted" before
attempting serious astronomical observations through the
telescope. Night adaptation normally requires about 10 to
15 minutes.
•
As you use your LX10 more and more for astronomical
observing, you will find that you are seeing finer and finer
detail—on the surface of Jupiter, for example. Observing
through a fine optical instrument is to some degree an
acquired skill. Celestial observing becomes increasingly
rewarding as your eye becomes better trained in the
detection of subtle variations of color, contrast, and
resolution.
7. Using the LX10 for Astrophotography
As discussed earlier, the LX10 is well suited for the
a s t r o p h o t o g r a p h e r, facilitating both long-exposure guided
photography or CCD imaging with its stable fork mounting, DC
electronic worm-gear drive system, and hand controller.
Astrophotography of the Moon and planets with a 35mm SLR
camera requires the optional #62 T-Adapter (Fig. 20).
Long-exposure, deep-space astrophotography of more than 5
or 10 minutes duration requires two telescope capabilities: (a)
a means of monitoring the precise position of the object being
photographed throughout the exposure, and (b) a means of
changing the telescope position very slightly to keep the object
in exactly the same position throughout the exposure.
Fig.20: 35mm camera mounted to telescope with T-Adapter.
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