Meade LX90-ACF Advanced Coma-Free, Instruction Manual

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MAINTENANCE

The LX90 is a precision optical instrument designed to yield a lifetime of rewarding applications.
Given the care and respect due any precision instrument, the LX90 will rarely, if ever, require
factory servicing. Maintenance guidelines include:

a.

Avoid cleaning the telescope’s optics: a little dust on the front surface of the telescope’s
correcting lens causes virtually no degradation of image quality and should not be 
considered reason to clean the lens.

b.

When absolutely necessary, dust on the front lens should be removed with gentle strokes
of a camel hair brush or blown off with an ear syringe (available at any pharmacy). DO
NOT use a commercial photographic lens cleaner.

c.

Organic materials (e.g., fingerprints) on the front lens may be removed with a solution of
3 parts distilled water to 1 part isopropyl alcohol. You may also add 1 drop of 
biodegradable dishwashing soap per pint of solution. Use soft, white facial tissues and
make short, gentle strokes. Change tissues often.

CAUTION: Do not use scented or lotioned tissues or damage could result to the
optics.

d.

Do not, for any reason, remove the correcting plate from its machined housing for
cleaning or other purposes. You will almost certainly not be able to replace the 
corrector in its proper rotational orientation and serious degradation of optical 
performance will result. Meade Instruments assumes no liability for damage
incurred to the telescope in this way.

e.

If the LX90 is used outdoors on a humid night, water condensation on the telescope
surfaces will probably result. While such condensation does not normally cause any
damage to the telescope, it is recommended that the entire telescope be wiped down with
a dry cloth before the telescope is packed away. Do not, however, wipe any of the optical 
surfaces. Rather, simply allow the telescope to sit for some time in the warm indoor air, so
that the wet optical surfaces can dry unattended.

f.

If the LX90 is not to be used for an extended period, perhaps for one month or more, it is
advisable to remove the batteries from the telescope. Batteries left in the telescope for 
prolonged periods may leak, causing damage to the telescope’s electronic circuitry.

g.

Do not leave the LX90 inside a sealed car on a warm summer day; excessive ambient 
temperatures can damage the telescope’s internal lubrication and electronic circuitry.

Collimation

The optical collimation (alignment) of any astronomical telescope used for serious purposes is
important, but in the case of the Advanced Coma-Free design of the LX90, such collimation is
absolutely essential for good performance. Take special care to read and understand this
section well so that your LX90 will give you the best optical performance.

As part of final optical testing, every Meade Advanced Coma-Free is precisely collimated at the
Meade factory before shipment. However, vibrations in shipping can cause the optical system
to become misaligned. Re-aligning the optics is, however, a straightforward process.

To check the collimation of your LX90, center a bright star that is overhead, or use a “hot spot”
of reflected Sunlight from a chrome car bumper, with the supplied 26mm eyepiece. Allow the
telescope to adjust to the temperature of your observation site before proceeding; temperature
differences between the optics and the outside air can cause distortion in the images.

With the star or hot spot centered,
de-focus the image. You will notice
that the out of focus star image looks
like a ring of light surrounding a dark
central spot; the dark central spot is
in fact the shadow of the secondary
mirror. Turn the focus knob until the
ring of light fills about 10% of the
eyepiece field-diameter. If the dark
central spot is offset in (i.e., not

Fig. 24a: Defocused star images.

(1)

(2)

(3)