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I will not attempt to describe this telescope except to say that I am quite happy with it.  Go to the Meade web site and read about the ETX-90 and it's big brothers, the ETX-105 and ETX-125.

This is what Meade says about the scope:

Manufactured at the Meade Irvine, California, facility, ETX Maksutov-Cassegrain telescopes produce superlative, diffraction-limited optical performance and resolution. Optics so high in contrast, image brightness, and resolution that ETX-90AT, ETX-105AT, and ETX-125AT models often outperform many telescopes of larger apertures.

What does it look like?

Here is a photo of my ETX-90 mounted on the Meade heavy-duty tripod.  I have modified the scope and subsequent photos will show my mods.

etx 90-1.jpg (99434 bytes)


I live on the second floor of a two-story apartment building.   The ETX-90 lives inside and I set it up on the rear balcony for viewing.  Here is the scope ready for operation.  (Yes, that's a bird feeder with seed and suet on the balcony -- Beaver Creek flows behind the apartment.)   This photo shows the scope with eyepiece covers in place on the finder scope and the eyepiece.

If you have not visited the Meade web site, do so -- they have much better photos than mine.

Update -- 28 October 2005

As of this date, my ETX-90 scope is no more.  In January 2005, we moved from Bristol, TN, to Bay Saint Louis, Mississippi.  On 29 August 2005, Hurricane Katrina destroyed Bay Saint Louis.  Our apartment was under five feet of water; furniture floated around in the flood and, when the water receded, some of the furniture came to rest against the scope, knocking it onto the floor where it was covered in six inches of mud.  The scope was ruined.  Here is a photo of the scope in its final resting place.

Fortunately, our belongings were insured and the insurance company paid promptly.  In October 2005 we moved back to East Tennessee -- Knoxville -- where we are picking up the pieces.  I'll probably buy another scope one of these days. 

Meanwhile, read on about the ETX-90.

Details and modifications

The ETX-90 is a computer controlled GOTO scope -- it has a small handheld paddle-shaped controller that controls the scope.  Small motors in the mount move the scope up, down, right, and left. 

Focuser extension

The ETX scopes focus by using a tiny knob on the back of the scope.  If the scope is fairly level, no problem.  But, if the scope is elevated, you simply cannot get your fingers onto the knob.  Several manufacturers make a flexible focus shaft -- use the hex wrench provided when you by the flexible shaft to remove the stock knob, attach the flex shaft.  Here's a photo.

flex shft.jpg (64467 bytes)

The flex shaft shown here is from Scopetronix.  Go to their site, look at the Table of Contents on the left side of the page, and click on the link to Meade ETX-90/105/125 Accessories.

Battery pack

The scope requires electrical power that can be provided by:

  • AA batteries installed in the base.
  • An adapter that plugs into a wall outlet and then plugs into a power cord from the scope.
  • A separate battery pack that provides longer life than the AA batteries.
  • I have all three but almost always use the separate battery pack.  Follow this link for a description of my battery pack.

Bubble level

The scope must be level and pointed north for alignment. I purchased a two-way bubble level at a hardware store and stuck it onto the base with double-sided foam tape.

level.jpg (69246 bytes)

ScopeTronix eyepiece shelf

When you use a scope, you will use several eyepieces during an observing session.   You need someplace to stash the eyepieces you are not using -- it's really not smart to stick them in your pocket, lay them on the ground, or put them anywhere else except on an eyepiece holder near or on the scope.  The ETX-90 comes with a shelf that mounts inside the tripod -- it is an excellent eyepiece holder -- but -- with it installed, you cannot fold the tripod legs.  I need to fold the tripod to move the scope inside and outside.  So, I installed an eyepiece holder sold by Scopetronix.  Here is a photo of it -- the eyepiece holder is the shelf shown in this photo.

 etx eyepce rack.jpg (86499 bytes)

The shelf has four holes for eyepieces and a slot to hold the Autostar controller.

There is one caution about this shelf -- note that the flex shaft hangs out of the end of the scope.  If the scope is elevated much above 35 degrees (which is not unusual) and the scope starts turning right or left, the flex shaft can catch on the eyepiece rack or on an eyepiece or the controller stashed in the rack -- watch for this and hold the shaft so it does not bind on the shelf -- otherwise, it could hang up and burn out a motor.

Power cord holder

Follow this link to see a power cord holder I made for my ETX scope.

GPS accessory

To align a GOTO scope such as the ETX-90, you must tell the scope precisely: date, time, and geographic coordinates.  Now, there is a routine in the controller where you enter your location and the scope remembers it.  Each time you use the scope, you must tell it the exact date and time and whether or not you are using DST.

Recently, manufacturers of GOTO scopes started adding GPS (Global Positioning System) capabilities to scopes as an option.  If you are not familiar with GPS, read about it here.

A company named StarGPS has produced a modification to the ETX scope software that makes it possible to feed a GPS signal to the scope -- the GPS information contains precise date, time, and location information.  Read about the StarGPS product here.

I purchased the StarGPS without the GPS receiver because I already own a Garmin GPS receiver.  The StarGPS package came with a cable that connected my Garmin receiver to the ETX controller.  Now, when I set up my scope, I go through this process.

  1. Set up tripod, level, and move the tripod so scope tube is pointed north.   Actually, I have marks on my balcony so I set the scope legs on the marks and the tube is pointed north.  DO NOT TURN ON THE SCOPE'S POWER SWITCH.
  2. Turn on the GPS receiver and let it find the GPS satellites.
  3. Plug the cable from the GPS receiver into the controller.
  4. When the GPS receiver shows it is locked onto satellites -- usually one minute -- turn on the scope.  The controller will display a notice that it is searching for the GPS information, then, it will show the GPS info -- date, time, location.
  5. Unplug the GPS receiver, you no longer need it.
  6. Now, go through normal alignment for the scope.

This photo shows the Garmin GPS receiver lying on top of the scope, getting a fix on GPS satellites.  The cable running out of the GPS receiver connects into the auxiliary connector ON THE AUTOSTAR CONTROLLER, as shown in the bottom photo.

etx garmin.jpg (88589 bytes)


garmin cable.jpg (91984 bytes)


A Warm Autostar is a happy Autostar

I discovered that when the Autostar controller gets cold -- when outside temperatures are below 30 degrees or so -- the LED display fades and becomes unreadable, although the Autostar operates normally.  Of course, if the LED display is not displaying, then the Autostar is of no use.  I tried heating it with a blow-drier -- it worked but every now and then I would have to heat up the Autostar.  Read this article for a solution that keeps the Autostar warm and happy.

Fixing A Broken Declination Knob

The declination locking knob on my ETX-90 broke -- to be exact, the stud that locks the declination clutch stripped out of the declination locking knob.  Read here about how I fixed it -- this fix should work for all ETX series scopes.

The Greatest ETX Information Site On Earth

If you own or are thinking about owning a Meade ETX scope, you need to go to this site, bookmark it, visit it 2-3 times each week.

Mike Weasner's Mighty ETX Site

This is a web site forum for ETX owners where you can:

  • Ask questions.  Mike or other ETX experts will answer you initial question and any follow-up questions you have.  Mike will stick with you until your problem is solved.
  • Make suggestions, share your experience.  If you have a tip or suggestion for the ETX family of scopes, post it here and share it with others.
  • Read what other people have to say.  If I have a problem with or question about how to do something with my ETX-90, the first thing I do is go to Mike's site and search around -- invariably, there's the answer.

Supercharge your ETX

Click here for my article about supercharging your ETX scope.


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