Last updated: 28 February 2002
This page is for user comments and information specific to the Meade ETX-90RA (originally known as the "ETX Astro") and the ETX-90EC. Comments on accessories and feedback items appropriate to other ETX and DS models are posted on other pages. If you have any comments, suggestions, questions or answers to questions posed here, e-mail them to me and I'll post them. Please use an appropriate Subject Line on your message. Thanks.

Subject:	ETX70AT or ETX90EC
Sent:	Wednesday, February 27, 2002 11:51:45
From: (Margaret Gibbs)
I have the 70AT and am enjoying it but wonder if I would be happier with
the 90EC.  I would get the autostar and electronic focuser.  Is there
really a wonderful difference that I would appreciate?  How about ease
of use?  I'm comfortable with the 70. Is it really convenient to use the
focuser?  Thanks
Mike here: The big difference is in the focal length, 1250mm vs 350mm. So you'll get more usable magnification out of the ETX-90EC. The focuser is not required but does reduce vibrations during focusing.
Subject:	Meade ETX 90AT
Sent:	Wednesday, February 27, 2002 2:44:06
From: (Paul Drez)
American Express is offering the ETX 90A as one of their "rewards
program" prizes.  Can someone tell me if they have any experience with
it, since I could not find any specs or discussion anywhere?

Paul Drez
Mike here: As far as I know, there is no "ETX-90AT" or "ETX-90A" model. There is an "ETX-90RA", also known as the "ETX Astro Model M". This is the original ETX model that does not have automated GOTO capability and dual electric drive control.
Subject:	ETX 90 / Barlow # 124
Sent:	Tuesday, February 26, 2002 11:30:19
one short question.

Got an etx 70, but sold it and will get a etx 90 tomorrow.

my question: will the meade barlow # 124 (which worked great with the
etx 70) also work with the etx 90, or do i need to buy the #128 model

many thanks for short answer.

b. rgds. from germany
Mike here: I don't have the #124 but it I think it will work but maybe not with all eyepieces. It depends upon the location of the focal planes of the various optical components. By the way, the #126 Barlow Lens is the one recommended for the ETX-90.


many thanks for you soon reply. Checked ist out today, works with all
Eyepieces i have.

Keep up your great site, regards

Subject:	494 Autostar with ETX-90/EC
Sent:	Monday, February 25, 2002 8:17:44
From: (Meyer-Lindenberg, Andreas (NIMH))
first of all I would like to congratulate you on your wonderful site. I
just got an Meade 60-AT with a missing manual and using the information
on your site it was no problem setting it up and getting going even
without a lot of observation experience.

I have a brief (I hope) question: I can already see that this scope is
too small and I want to upgrade to a 90 or 125/EC. Can I use the 494
autostar that I already have to control these scopes?
Thanks a lot,
Mike here: According to the info in the article "Autostar Models" on the Autostar Information page, the #494 can only control the ETX-60 and ETX-70.
Subject:	ETX-90RA on ETX-70EC base?
Sent:	Friday, February 22, 2002 8:47:18
From: (chappy)
Can an older etx70 ec (not AT) computerized base be attached to an etx
90 ra?


Dave Hodge
chaplain US Army Hawaii
Mike here: You would need to make your own tube adapters for starters to attach the telescope tube to the forks. But I've not heard of it being done with the ETX-70EC model.
Subject:	More on Baffle
Sent:	Wednesday, February 20, 2002 14:23:33
From: (Rose)
Well yea!  :-) I like my little scope. I want it fixed, and I would like
to do it myself. I'm an owner, and I would imagine this will happen
again, so I decided to do it myself. It's already out of warranty so
what the heck.
Does this happen often?
Mike here: Does WHAT happen often? Bouncing telescopes in the back of a truck, resulting in damage?


Since I do not know your personality, I am in great hopes that you are
just kidding with me and not irritated with my many questions. I never
dreamed anything like this would happen. I bought the telescope when it
was fresh on the market and as you know the ETX 90 Astro has depreciated
greatly since that time. I am self taught and it has taken me awhile to
learn the things you should know about a telescope before you buy one.
I, as all newbies are, thought I would see the views that are
advertised. The beautiful colors of the nebulas, etc. You must know/or
remember what I am talking about. I have put a great deal more money in
it than it is worth now, and besides even though it is only a 90mm, it
does have a pretty good view. WHEN IT IS NOT SLIP SLIDING AWAY! Sooooooo
I have no intentions of letting it ride in the back of a truck again,
but I would like to know if the baffle moves around like this often. I
would like to be able to avoid this in the future, and I would like to
know that there is someone out there willing to answer the questions of
a very inexperienced observer.

              Thank you again       Roz
Mike here: Yes, I was kidding about the pickup. But as with all precision instruments, care must be taken when moving it, whether in or out of a proper case. Clay Sherrod noted in one of his articles on the ETX Site to treat your ETX like a baby. If you do that you'll have years of great views from it. I took my ETX-90RA to Australia back in 1999 (when it was three years old) and didn't have any problems. I carried it as carry-on but it was in a soft-sided case and saw lots of handling from planes to cars to hotel rooms to parking lots, etc. So, no, the baffle should not move around with normal care. As noted on the Site several years ago, my baffle had slipped a little bit and others have noted this with the original ETX model (circa 1996). The problem was the glue used at the time of assembly; Meade corrected that years ago. As to questions, there are no dumb or annoying questions; we all have been (and continue to be) in situations where we learn from others, either by reading what they've already said or by asking questions. One of the nice things about the ETX Site is the worldwide community of support that has been established in the 5+ years the Site has been online.

And continuing:

Whew! Glad to hear you were kidding. Bye the way, I did not just throw
the ETX in the back of the truck. It was in the case made just for it. I
did take some precaution on how it was packed as well. I'm going to
assume it was the heat.  Glad to hear Meade fixed the glue problem. Now
to the attempt to fix it. I'll let you know how it goes. Also, I've been
through a couple hundred web sites on telescopes and the ETX is by far
the most extensive I have seen so far. Thanks again. I appreciate you
taking the time to answer my questions. Now that I know you were kidding
it would appear you've enjoyed my mishap. I'll try not to bring you such
pleasure in the future. :-). Who knows you might just guide me into
feeling as comfortable as you do in taking a telescope apart. Right now
it's a little scary. Thanks again  Roz
Mike here: I didn't enjoy your pain and I do suffer when I hear of your reports like yours. But I also recognize that I could just as easily been the one who had the mishap! And you're right, excessive heat can do a number on glue, hence another one of Clay's precautions about treating the telescope like a baby and don't leave it where it will get hot. I don't feel comfortable taking ANYTHING apart and I won't unless it is an "absolutely positively can't be done any other way" type of thing. The ETX Site has a bunch of enhancements that can improve the performance of the ETX but I've never felt the need to get that last few percent of performance.
Subject:	ETX, of course :-)
Sent:	Tuesday, February 19, 2002 12:46:55
From: (Rose)
I got your name in several different places.:-)
Anyway I need some advise from someone who knows the ETX.
I took a trip this summer and I took my ETX 90 Astro with me. Not
knowing it travaled under a bed cover in a case in the bed of a pick up
truck. Now the baffle has slipped downward and off center. After taking
the front lense off of it. I realized what the problem was but don't
know what I should do to fix it. Got any suggestions?

                                          Thank You 
Mike here: Your best choice is to return it to Meade for repair and recollimation. Will probably cost you $75. If you want to try it yourself, see the articles "ETX-90RA Secondary Baffle Fix" on and "Re-attaching the Baffle" on the Telescope Tech Tips page. You will likely need to recollimate the telescope and there are articles on the Telescope Tech Tips about that. Keep in mind you can do more damage if you make a mistake.


Thank you for the information. I really hated it when I took the scope
from the case and saw the baffle.


I read your article. I'm concerned about the corrector plate. Can I harm
it in any way.
Mike here: Yep, you can scratch it, you can ding it, you can damage the coating. Scared yet?
Subject:	Collimating ETX90
Sent:	Thursday, February 14, 2002 0:49:39
From: (Andrea Perfetti)
my two years old ETX90-RA has started to sho the problem related to the
shift of the baffle on the secondary mirror. For now the shift is very
very small and it should not be a problem. Howewer the diffraction rings
are not uniformly bright, they are brighter on one side when observing a
perfectly in focus star. I'm thinking to follow the many posts about
recollimating but there's a thing that I was not able to find in the
archive: I need to know if it is necessary to exclude the flip mirror to
do a reliable test for collimation procedure and to use instead the
visual back.
Hope to receive an answer by someone...
Many thanks in advance and keep up the good work

Andrea Perfetti
Mike here: For accurate results you should go straight through. However, keep in mind all the caveats about doing your own collimation; you can make things worse than they were! If you do attempt it, let me know the results.
Subject:	New ETX owner says "thank you", and has a question.
Sent:	Wednesday, February 13, 2002 23:11:26
From: (Douglas Braun)
Your ETX Web site is wonderful!  Without it, I can't imagine how anyone
would manage to figure out how to get their ETX to work well.

Anyway, my ETX90 has a lot of slippage and backlash in Azimuth
(Elevation is perfect), and I'm trying to track down the problem.

I suspect that the scope's Az bearing is set up too tight, and it has
too much friction for the motor to turn it without slipping.  When I
loosen the Az clutch completely (and I mean really completely), it takes
what seems like a lot of torque to turn the scope by hand. I rigged up a
small stick and a kitchen scale to measure the torque required to rotate
the scope in Azimuth, and I got 93 in-oz, which is the same as 5.81
in-lb, or 0.48 ft-lb.

Do you have any idea if this sounds reasonable?  If I had one or two
other ETX90's sitting in front of me, I could simply compare mine to
them, but unfortunately don't know any other owners locally, and there
is no dealer with one on display anywhere near where I live.

Thanks so much,

Doug Braun

P.S.: Will your book be sold in Barnes & Noble or any other bookstores?
Mike here: You don't say which model ETX-90 you have, how old it is, or whether you are using the Autostar or the Standard Handcontroller. At any rate, you can try distributing the gear grease by rotating the ETX in azimuth several times in one direction and then the other. As to the book, I have seen other titles in the Practical Astronomy Series in Borders stores. So I would expect it should show up in B&N.

And an update:

The scope is an almost-new ETX-90EC.  I finally bit the bullet and
decide to adjust the Big Nut under the AZ gear.  It turned out that the
factory had set it really, really tight.  There were already a bunch of
little Teflon bits accumulating in the bearing.  I adjusted it so that
the AZ motion seemed about as tight as the EL motion.  It works MUCH
better now!  The AZ rotation is very smooth and has hardly any backlash.


Subject:	RE:RA is sticking and jerky (Rita Comuzzi)
Sent:	Wednesday, February 13, 2002 10:21:56
From: (Fernando Pertuz)
I'd like to contribute my experience on this problem.

When my old (but still loved) ETX-RA became sticky and jerky when
tracking, very critical when you are at 10 degrees latitude, I blamed it
on everything: Balance, loose or tight RA nut, lubrication ... etc.
until I discovered the origin of my woes.

Along the edge of the scope's base, just below the lower edge of the RA
setting circle there are three evenly spaced bearings where the scope's
moving part meets the base. One of these bearing was missing. Since I
could not find an adequate replacement for this bearing, I removed the
remaining two and put in their place three slivers I cut out of teflon
and it did the magic.

The movement is again smooth as it used to be.

Fernando Pertuz

Subject:	Upgrade Meade ETX
Sent:	Tuesday, February 12, 2002 22:46:00
I have a Meade ETX 90 RA.  Does Meade offer any base upgrade so that I
can use Autostar?  Thank you.

Michael D. Abraham
Mike here: This is discussed on the FAQ page on my ETX Site.
Subject:	RA is Sticking & Jerky
Sent:	Monday, February 11, 2002 20:39:30
From: (Rita Comuzzi)
I'm having trouble with my ETX RA, when I first got it, it was buttery
smooth in the RA movements.

As time went on it got jerky and jumpy.  I've taken off the bottom and
done a visual inspection of the insides.  I've also tried various
combinations of tightness with the screw that holds the battery and
motor compartment to the scope.  I've replaced the Teflon pads and
that's ok.

Does it matter where the scope mounts to the battery compartment? At
present I have the rear of the scope between the two rear leg holders.

Would any type of lubricant be of any value?

I have searched and found an idea by Dr. Clay  on sticky RA adjustments
but a search of the site didn't reveal any further info.

Any way thanks for the ear and this is the best ETX site on the web.


Bill Unger
And from our resident hardware expert:
From: (Clay Sherrod)
I work on ETX RA's is a neat scope to work on and there are
inherent problems that it runs into just like all of the scopes out

This problem is very common and I just fixed my brothers not too long
ago. There is likely a point of resistance that the telescope and/or the
drive system is encountering; this can be a result of balance problems
in the past, a bump that the scope has taken recently, or just wear. 
The ETX RA is amazingly resistant to normal wear and it is likely that
something has started interfering with the free motion that the RA axis
needs; my first impression is that the locking clutch has a "high point"
on it and merely needs to be either adjusted or refitted.

The technique of slightly clamping the RA lock and them manually turning
(gently!) the axis by hand back and forth for about 180 degree swings
usually will reseat both a dragging clutch and a parts mismatch in the
RA axis if there is one....simple, but effective!


Subject:	ETX 90 RA
Sent:	Thursday, February 7, 2002 12:45:11
From: (Botts, Steve)
I apologize if this has been covered, but I didn't find it in the site.

I own an ETX 70 and often visit your site.  I have been noticing a lot
of ETX 90 RA's for sale at great prices recently.  I know this does not
work with Autostar.  But is it the same quality of optics as the current
ETX 90 ECs?   It seems worth buying one just for looking at the planets.

Thanks-and thanks for the great site.

Mike here: They are two different types of telescopes with different purposes. The ETX-70AT is a short focal length refractor (350mm, meaning less magnification) whereas the ETX-90 is a Cassegrain-Maksutov with a much longer focal length (1250mm). If you want to observe details on planets you will likely be disappointed in the ETX-70AT. It is more intended as a wide-field instrument although you can see cloud bands on Jupiter and the Rings of Saturn with it. They just won't appear as large or as detailed as they would in the ETX-90.


Thanks for your prompt reply, Mike.

I shouldn't have introduced the red herring of what I currently own.
Actually my question was between the ETX 90 RA and ETX 90 EC.  I
understand the mount differences and the lack of computer control on the
RA.  But are the optics identical?  They are offering the RA for about
$220.  That is quite a deal, if the optics are just as good.   And I can
FIND the planets, so I am not sure I will miss the Autostar on this one.
(I have the 70 plus my old 6 inch Newtonian for deep space.)


Mike here: Yes, the ETX-90 telescope itself it is the same on the RA and EC models. Only the base, drive, forks, and electronics are different.
Subject:	Dec/alt stopped working
Sent:	Tuesday, February 5, 2002 20:27:57
From: (Bob Vilums)
Sorry to bother you so much but the Dec/Alt (up and down) on my ETX 90EC
stopped working.  I can't seem to tighten the wheel.  It appears to be
stripped.  Is there a simple fix for this, or should it go back to the
factory.  This scope is only a week old.
Thanx once again,
Mike here: If only a week old I would contact the dealer for a warranty exchange. However, you can also contact Meade about a replacement for the Right Tube Adapter, which is like the component that has failed (either due to a manufacturing stress or overtightening of the axis lock). Replacing the RTA is simple and can be seen at the bottom of this page on my ETX Site:


Thanx again Mike,
Your speed in responding is overwhelming..  You should be named the
patron saint of ETX users..

And an update:
When I took the RTA off I noticed that the plastic shaft had not sheared
off like the one you have displayed at your website.  The brass bushing
had simply came out.  I plopped it back in there and the RTA worked for
about 15 minutes and the bushing came out again.  Does the new RTA come
with a new bushing?  Would it be safe to glue the brass bushing into the
plastic shaft?  It mearly looks stripped inside there. I can't believe
that the RTA is so poorly designed.  What were they thinking?

Mike here: The new RTA is a complete unit. And yes, you could epoxy the bushing. Like you, I suspect that plastic has just stripped. The design wasn't necessarily bad, just the materials used in a particular batch of RTA.
Subject:	RA upgrade
Sent:	Sunday, February 3, 2002 19:59:16
From: (Douglas L. Smith)
Is there a way to upgrade an RA to a newer EC fork and electronics? The
OTA is the same aren't they?

Mike here: This is discussed on the FAQ page.
Subject:	ETX 90 EC / Autostar 497
Sent:	Sunday, February 3, 2002 18:27:43
From: (Gary Sparkes Sr.)
I just purchased an ETX-90EC and Autostar 497 Controller.

Out of the box .... " Motor Fault " indication on controller.

I thus installed fresh batteries, i know the original set was fresh but
was willing to try a new set.

I "trained" the motors and proceeded to do alignment.

I must explain all the testing was simulated, that is done indoors.

I did the "easy" alignment, similated centering the two
stars.....Alignment Successful.

I than proceeded to put the ETX 90 through some paces. I told it to GOTO
three different items in sequence.

Sirius (Star)
Pollux (Star)
Virgo (Constellation)

Sometimes I could make it through this sequence several times before the
" Motor Fault " appeared.

I did this with two different sets of batteries as this was the only
suggested action that applied. ( there was nothing overloading or
binding the ETX )

Is there something I missed????

I purchased this scope on 01/28/2001 so I do have and am prepared to
exercise the option of returning the scope for an exchange. Is this
worth the effort, or will the next scope have the smae problem? How
comon is this problem, and is it something that will recur?

Any ideas will be appreciated.

Gary G. Sparkes Sr.
Mike here: Some thoughts: check the telescope model in the Autostar, check the proper HOME position (did you do the rotations?), do a RESET, reCALIBRATE, and reTRAIN. You might also check the connections and rotate the telescope by hand (with the locks unlocked) through several rotations and up/down to loosen the gear grease.


Thank for a quick response and the ideas. I did the proper HOME position
according to instructions ( full counterclockwise rotation, align over
computer control panel, level tube, and point north ). Probably the only
thing I did not do was manually rotate through several rotations. I did
however go through several rotations with the standard controller.

What is with this grease? I mean, perhap the grease should be removed
and a different lubricant applied. I imagine if it is sensitive to the
grease that this problem could be more persistent if the scope is used
outdoors in cold weather.

This problem would never have been discovered if not for the purchase of
the Autostar 497.

One quick thought, I do remember seeing the display " flicker " on the
497 as the scope was slewing and at times tracking, this led me to think
of connections, but the cable was fully inserted on both ends. I could
not duplicate the 'flicker'by wiggling the connectors on either end.

You have a GREAT site, it's the first one I went to, since the others
that GOOGLE led me to were commercial.

I think once I get this worked out I may send my scope out to be

Thanks Again,
Gary Sparkes
Mike here: Since the scope was new, the grease can become "settled" and stiff during storage. So, the rotations help distribute it. You don't need to do the grease redistribution every time. As to the flickering you saw, that does indicate an electrical problem someplace: cable, connectors, ETX circuit board, or Autostar circuit board.

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