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Meade ETX-70AT:
My Modifications

You should have come here from my amateur astronomy page.   If not, after reading this article, click on this link to go to that page.

In early January 2003 I purchased a Meade ETX-70AT 70mm refractor telescope with the Meade Model 494 Autostar computer.  For a description of the telescope, go to the Meade site.  After two nights of observing -- with temperatures between 8 and 10 degrees (F) I made two modifications to the scope; the mods are described here. 

Mike Weasner's Mighty ETX Site

If you own a Meade ETX scope (60, 70, 90, 105, or 125), or if you are planning to buy on, or contemplating buying a telescope, you need to visit Mike Weasner's Mighty ETX Site.  He is an ETX owner who is a real guru on the ETX family -- so much so that Meade, the manufacturer, sends people to his site.

Mike's site includes:

  • Articles about every possible aspect of the ETX series of scopes, the Autostar controller, and associated equipment.
  • How-to, tips, tricks, solutions, recommendations, experiences.
  • E-mail articles.  If you send Mike an e-mail with a question (He encourages people to do so -- and he answers the e-mails personally !!!) he posts your e-mail and his response so folks who visit his site can see what problems and solutions others have had.


First, however, let me tell everyone my experience with batteries, the ETX-70, and cold weather.  The scope has a computer-driven guidance system that uses six AA batteries to supply nine volts to the computer and to the motors that drive the scope up and down.   Cold weather is tough on batteries -- battery output falls dramatically as temperature drops below 30 degrees F or so.  The six AA batteries just don't last very long, especially with the load of the scope's motors and computer.  I put fresh batteries in in the scope on Monday night and observed for 90 minutes on Monday and 30 minutes on Tuesday.  While I was in the midst of tracking a star on Tuesday, the scope suddenly stopped moving and the computer showed the error message "Motor Unit Fault." 

I thought the scope had failed and I would need to do something drastic, possibly even send it back to the factory.  I quickly e-mailed Mike Weasner who suggested that I change the batteries and try it before doing anything else.  That was it -- the combination of cold weather and heavy use drained the batteries.

Meanwhile, I had ordered the AC power adapter from Scopetronix.  It arrived on Wednesday.  I used the AC adapter for observations the rest of the week and the scope performs flawlessly.  I recommend you buy this adapter for your ETX scope -- it has a 25-foot long cord and, with an extension cord, you can use it easily in your back yard.

Now, let me show you my modifications to my ETX-70AT

Storing the power cord from the AC adaptor

While the AC adaptor eliminates the need for batteries, it introduces another problem -- what to do with that cursed 25-foot-long power cord when the scope is stored.  The power cord attaches to the battery plug inside the battery compartment.  When you are finished using the scope, you could open the battery compartment, disconnect the AC adapter, and store it separately.  I elect to leave the cord connected.  So, now I have a scope on a tripod with 25 feet of power cord wound up and piled at the foot of the tripod. 

No more.  Here is a photo of a power cord mount that I made one Sunday afternoon -- took 10 minutes to design, build, and install.

crdhldr-1.jpg (341258 bytes)               crdhldr-2.jpg (317120 bytes)

The photos are self-explanatory.  I cut a piece of 1 X 2 poplar 8 inches long.  Using a saber saw, I cut each end, not straight, but curved as you see in the photo.  Then, 1-1/2 inch from either end and 3/4 inch from the bottom of the poplar piece, I drilled two 1/4-inch holes.  I used two nylon electrical cable ties to lash the poplar strip to one leg of the tripod.  The power cord wrapd around the poplar strip, neatly out of the way.  No holes drilled into the tripod leg -- just cut the nylon cable ties if you need to remove the cord mount.  You could paint it if you wish.

Change the focus knob

The ETX scopes are nice scopes.  The ETX-70 is the minimum recommended for astronomical observations; the 90, 105, and 125 are very competitive with other scopes of their size and price range.  BUT -- Meade did not do a good job of designing the focus knob.  Look at this photo of the focus knob on my ETX-70AT.

fcs-knb1.jpg (270702 bytes)

See the knurled, chrome-silver knob in the center of the photo?  That's the focus knob -- turn it and it moves the lens in and out to focus the scope.  It's fine when the scope is positioned as in this photo -- sitting level.  BUT, when you elevate the scope past about 30 degrees, the focus knob disappears into the mount and it is extremely difficult to focus the scope.  If you have big hands or are wearing gloves, you cannot get your fingers on the knob.

Here's the solution.  The ScopeTronix Flexi-Focus (TM).

fcs-knb-2.jpg (217753 bytes)

It's a simple device -- a flexible shaft with a shaft coupler on the scope end and a nice big knob on the other.  The original knob has a set-screw that attaches it to the focusing control of the scope.   The Scopetronix device comes with an Allen wrench to remove the original knob and install the flexible shaft in its place.  The whole operation takes less then two minutes and you'll wonder how you lived without it.

Go to the Scopetronix site; look at the left frame; scroll down to the link for ETX-60/70 Accessories and there it is.

Removing the lens cap made easy

Look at this photo of the lens end of the scope.

lns-cvr.jpg (165785 bytes)


What you are looking at is the lens cap.  Inside the lens cap is a threaded rim that screws into the front of the scope to protect the lens.  To remove it, simply unscrew it -- unless the temperature is 10 degrees, making the plastic lens cap cold and slippery and your fingers stiff.  Under those conditions, it's not easy to remove the lens cap.  Why didn't Meade put a small handle or some other grip on the lens cap?

Well, I did.  See the little button on the lens cap?  That's my modification.  Visit you local hardware or gadget store and look for self-adhesive, stick-on vinyl protective bumpers.  Be certain to get one that will stick up enough for you to grip it.  Take the lens cap and the vinyl button in the house and let them get warm before sticking the button onto the cap.  Be certain to put the button on the outside edge of the cap, as pictured here -- that gives you more leverage.

Now, to remove my lens cap, I can keep my gloves on, put a finger on the side of the vinyl button, and spin the cap off -- and back on.

Adding a finder scope

The ETX-70AT comes without a finder scope.  I added two finder scopes to my ETX-70:  (1) a Meade 8X50 finder scope made with a mount for the ETX-70, and (2) an Orion EZFinder reflex finder.  Go to this link to see the finder scopes on my ETX-70



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