Meade LXD75 GOTO Mount
Copyright (c) 2004 Cloudy Nights Telescope Reviews
by John Crilly
Meade’s LXD75 is their current medium - duty German equatorial
telescope mount. It replaces the LXD55 model and is intended to
compete with the Celestron CG5- GT and the Orion Sky View Pro.
Copyright (c) 2004 Cloudy Nights Telescope Reviews
Like all of those, it is an imported unit derived from Vixen’s Great Polaris
mount with a payload capacity for visual use of approximately 30 pounds.
It accommodates a variety of optical tubes through the use of a Vixenstyle saddle plate. The LXD75 mount is supplied with dual axis motors
and either a dual axis manual controller (EC models) or Meade’s popular
Autostar controller (AT models). An LXD75EC can be converted to
Autostar operation by simply replacing the EC controller with a #497
Autostar. Meade supplies a new steel tripod with this model. The mount’s
motors and controllers operate from 12 Volts DC and it is supplied with a
battery pack for 8 D cells.
Copyright (c) 2004 Cloudy Nights Telescope Reviews
It is equipped with an illuminated polar alignment telescope. The cap for
this polar finderscope is retained by the illuminator, pictured here.
Optical tube options include 5” and 6” achromatic refractors, a 6”
Newtonian reflector, an 8” Schmidt - Cassegrain, and 6”, 8”, and 10”
Schmidt - Newtonians. Currently, Meade is supplying their Lunar Planetary
Imager and the Autostar Suite software with the AT models. Although the
mount provides no conventional autoguide port, the LPI and Autostar
together do permit autoguiding of this mount. Of course, an external
laptop or PC is required.
The Autostar controller provides GoTo and tracking operation, with a
database of over 30,000 objects in its user- updatable 1MB Flash
memory. Slew rates from sidereal to 4.5 degrees/second are user-
Copyright (c) 2004 Cloudy Nights Telescope Reviews
selectable. Meade specifies the pointing accuracy as being within 15
arcminutes. This will suffice to place objects within the center half of the
field of view of a 52 degree Plossl at 100X. Meade has issued a long
series of user- installable firmware updates for this controller, both to
improve operation and to add new features such as PEC and cone
correction (three star alignment).
Opening the shipping box reveals a well - packed unit with a fairly high
degree of fit and finish. Castings on the mount and tripod are cream in
color, while the tripod legs are bright steel and the motors and controller
are black. Once assembled, I found the mount to be more attractive than
the gray LXD55 units. Meade has again failed to provide a holder for the
handbox, but as always Velcro proved to be the answer to that.
What it does
This is an equatorial mount; that is, it is designed so that once the RA
axis is pointed toward a celestial pole a celestial object can be tracked by
operating a single constant - speed motor. This provides accurate tracking
plus it avoids field rotation, both of which are advantageous for imaging.
Switching between optical tubes is a matter of loosening the saddleplate
bolts, lifting the dovetail from the saddle, and inserting the other
telescope’s dovetail into the saddle.
With the Autostar controller option (AT models), after a simple two or
three star alignment procedure the mount can be commanded to
automatically slew to any of the 30,000 plus objects in the unit’s
Copyright (c) 2004 Cloudy Nights Telescope Reviews
What a user should know
As with any equatorial mount, the user should be somewhat familiar with
the celestial coordinate system. This means that the user’s vocabulary
should include right ascension, declination, sidereal motion, celestial
pole, and such concepts. The user manual, like most such manuals,
doesn’t make much of an attempt to educate the user in these topics, so
it’s up to the user to bring that knowledge. The mount can be used by
someone with little or no knowledge of these concepts, but the confusion
and frustration level of such a user is sure to be higher than those of
someone who has done his or her homework.
Setting it up
Copyright (c) 2004 Cloudy Nights Telescope Reviews
Setup is straightforward. The tripod is shipped with the spreader and
mounting bolt packed separately, so assembling the tripod is the first
step. The spreader is installed onto the mounting bolt and the bolt
suspended from the tripod head’s center by the supplied C clip. This step
is poorly covered in the manual, and a number of new users found the
procedure confusing.
This is the proper order for the parts on the spreader bolt. The “C” clip
shown goes above the tripod head, all other parts below it.
The latest revision of the manual is available on Meade’s website and
does address this assembly. The mount can then be installed. Like the
LXD55, the tripod head has the azimuth adjusting dog permanently fixed
so one leg is always oriented toward the celestial pole.
Copyright (c) 2004 Cloudy Nights Telescope Reviews
Loosening the azimuth adjustment bolts on the mount to provide a gap
for this dog, the mount is lowered onto the tripod head. Then the
mounting bolt is extended upward into the bottom of the mount and
tightened to hold the mount securely. Next, the spreader is pulled tightly
against the tripod legs with the supplied handnut on the mounting bolt.
Next, the counterweight shaft is attached to the mount and the
appropriate number of counterweights installed. Be certain to install the
counterweight retaining screw at the end of the shaft after this is done.
Copyright (c) 2004 Cloudy Nights Telescope Reviews
Then the optical tube’s dovetail is inserted into the saddle. Except for
assembling the tripod and tightening the spreader, all these procedures
are precisely the same as for the LXD55 model. There are several
additional steps which may be performed for best performance, but I
have found that they aren’t necessary for visual use. The user is referred
to the manual for these procedures, including alignment of the polar
alignment telescope to the RA axis and alignment of the dovetail for
orthogonality. Finally, the power source, DEC motor cable, and either the
EC controller or the #497 Autostar is plugged into the control panel on
the RA drive assembly.
Copyright (c) 2004 Cloudy Nights Telescope Reviews
Using the mount
First, the optical tube must be balanced in both axes.
DEC axis balance
RA axis balance
Next, the RA axis must be pointed at or near the Celestial Pole. There are
several ways to achieve this; I’ll describe the quick system I have used
which suffices for visual use. Imaging will require a more complex setup
to achieve the higher accuracy required. Even without aligning the polar
alignment scope to the RA axis it can be used for a quick polar setup. I
have found that in the Northern Hemisphere simply adjusting the azimuth
and elevation bolts
Copyright (c) 2004 Cloudy Nights Telescope Reviews
to place Polaris near the center of the polar alignment scope will permit
accurate GoTo operation and tracking sufficient for extended viewing of a
given object at reasonable magnifications. Polaris is fairly close to (within
about half a degree of) the North Celestial Pole. At this point, the mount
should be ready for manual operation with the EC controller. The
telescope may be aimed by either slewing with the dual axis motors or by
releasing the clutches and moving the telescope by hand.
DEC clutch lever
RA clutch lever
Once an object is found, tightening the clutches will enable tracking,
keeping the object in view as it appears to move across the sky.
Copyright (c) 2004 Cloudy Nights Telescope Reviews
To use the Autostar, some additional steps are required.
Date/time /location / time zone information must be entered. The drives
must be trained (usually only once) and the Autostar must be aligned
using a two or three star alignment procedure. This is begun by placing
the mount into the Polar Home position.
I should mention that the mount is supplied with arrow stickers on both
axes to indicate the polar home position. I feel that it’s best to rotate the
DEC axis 180 degrees away from the position shown by the arrows. It
makes no operational difference, but the saddle retaining bolts are
oriented such that they will hold more securely this way. In the photos
above,the picture on the right shows the arrows aligned. The picture on
Copyright (c) 2004 Cloudy Nights Telescope Reviews
the left shows my preferred home position. Next, the alignment
procedure begins, in which the user centers the alignment stars after the
mount moves to where it thinks they are. After star alignment, an
optional Polar Alignment procedure becomes available to refine the polar
alignment of the mount. Once alignment is achieved, the Autostar
controller permits objects to be selected from any of a large variety of
internal catalogs. It also has built - in “tours”, which select items which are
above the horizon from lists which have been previously installed. Several
of these are supplied in the standard firmware and many more are
available online from a variety of sources.
So - how well does it work? My LXD75 is the AT version, which includes
the Autostar controller. To verify that all was well I first assembled the
mount indoors. This is the best way to initially check out any automatic
telescope mount, as it permits the user to see what it is doing and
diagnose any problems in a comfortable, well- illuminated environment. I
checked the gear engagement and setscrew tightness on the transfer
gears in both axes and observed no problems. There are inspection
hatches in both drive assemblies:
RA inspection hatch
DEC inspection hatch
I did notice some minor slop in the DEC axis and adjusted the
worm /worm gear engagement on the DEC axis (a simple procedure) to
eliminate that.
Copyright (c) 2004 Cloudy Nights Telescope Reviews
That’s the only adjustment this unit required. I then powered it up and
entered date/time /location / ti me zone information. I lied to it about the
time, choosing an evening hour at which I knew where many objects
would be in the sky. This permitted me to do a reality check - if the
mount pointed to where I knew an object should be I’d know it’s probably
working correctly. I aimed the RA axis at about where Polaris always is,
and began a three star alignment. When it slewed to the alignment stars,
I could see that it was about correct. Accepting it’s guesses as to their
positions, I was then able to slew to a variety of object around the sky
and observed that the directions to which it pointed consistently made
sense. With the confidence gained from this, I was ready to take it out
into the dark.
I used the mount at our Club’s observing site several times, and used it at
Astrofest for our dual Solar viewing setup (Ha and white light).
Copyright (c) 2004 Cloudy Nights Telescope Reviews
I used the mount with the 8” Schmidt - Newtonian optical tube, a 120mm
F/8 refractor, and with a 6” F/8 refractor plus a piggybacked 80mm F/11
refractor. The SNT and the larger refractor are substantial loads for such
a mount, and both had previously been shown to cause instability with
the LXD55’s extruded aluminum tripod. The LXD75 had no problems with
these setups. The dual- refractor rig is a Solar observing setup, so it
normally remains pointed at one object for extended time periods.
Tracking was very good; the Sun was always there when we returned to
Copyright (c) 2004 Cloudy Nights Telescope Reviews
the telescope. The SN- 8 was used for miscellaneous deep sky
observations and the GoTo accuracy after a good drive training and
careful three star alignment was fine; objects were nearly always within
the field of view at 100X. Settledown time with either setup was a few
seconds. The motors are noisy, as are those on all of the automated
Vixen clones. There’s a Quiet Slew option in the #497 handbox for those
who are concerned about this. That option reduces the maximum slew
speed one notch and it does make a difference but it’s never silent while
slewing. Tracking, on the other hand, is silent.
Fit and finish on this unit were quite good. I found the cream and black
color scheme to be very attractive; similar to that of the Vixen Sphinx:
. The new tripod is great. The polar alignment scope illuminator is very
nice, as is the fact that the polar alignment scope is included. The
Autostar is one of my favorite controllers, and the LPI is a fine accessory
for it. The motion in both axes is more free than in any other Vixen
clones I’ve used, which makes balancing the system much easier.
The clamp bolts on the tripod legs are small and difficult to tighten with
cold fingers.
Copyright (c) 2004 Cloudy Nights Telescope Reviews
A quieter drive system would be nice. I wish Meade would offer this
mount bare, with no optical tube. A handbox holder would be a good
addition. The “North” peg on the tripod head can’t be moved, which can
cause problems at some latitudes. The castings are still made of what
appears to be very soft aluminum alloy.
Comparison with LXD55
Obvious questions arise regarding comparisons between this mount and
the previous LXD55. They are more similar than different - but here are
the contrasts I noticed. The steel tripod is a vast improvement due to
stronger legs and the addition of a leg spreader. The polar scope
illuminator now has a dimmer and a real power switch - and the cap has
a retainer! The mount has ball bearings in both axes and is distinctly
smoother and more free in its action. Both saddle plate retaining bolts
are larger. The current Autostar firmware provides PEC and a three star
alignment procedure to correct for cone error, though of course an
existing LXD55’s controller can easily be updated to that revision.
Functionally, the LXD75 is very similar to the LXD55; the only operational
improvements I observed were increased tripod stability and smoother
axis motions. I should comment that I have owned several LXD55’s, and
have always experienced good performance with those after minor
adjustments and/or setscrew replacement.
Click to discuss article in the forums
Copyright (c) 2004 Cloudy Nights Telescope Reviews
The mount reviewed was purchased “blind” from Oceanside Photo &
Telescope by the author. The author has no commercial relationship with
Meade Instruments, OPT, or any other astronomical manufacturers or
retailers. All photos are the property of the author and permission is
granted to Cloudy Nights for their use in conjunction with this article.
Some photos are from an LXD55; they were carefully chosen to be
representative of both models and do apply to this topic.
Further reading suggestions:
The following articles on Cloudy Nights may be helpful to someone
considering this mount, or to someone learning how to use it
CG5- GT review - http: / / w /lab / m ounts /asm.pdf
LXD55 review - http: / / w /lab / m ounts /asm.pdf
LXD55/75 setup guide - http: / / w /mounts2 / l xd55 check.htm
Choosing an alternate power source http:/ / w /howtos2 /power.htm
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