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Last updated: 31 January 2011
This page is for comments and user feedback about ETX telescopes. ETX models discussed on this page include the ETX-60/70/80/90/105/125 (EC, AT, BB, Premier Edition). This page also includes comments and feedback of a general nature. Comments on accessories and feedback items appropriate to the ETX-90RA, DSX, 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 for posting. Please use an appropriate Subject Line on your message per the Site Email Etiquette. Thanks. Remember, tips described on this site may invalidate the warranty on your telescope or accessories. Neither the submitter nor myself are responsible for any damage caused by using any contributed tips.

Subject:	EXT 125 sudden movement
Sent:	Sunday, January 30, 2011 09:54:16
From:	James West (
When using the scope it will suddenly slew up about 20 degrees and may
do this several times.

This EXT scope is the first generation I think, I purchase it in 1999. I
have the latest firmware for the Autostar.
James R. West
Mike here: See the item "Q. My telescope has gone berserk. It slews until it hits the hard stop in either azimuth or altitude. It behaves erratically. What do I do?" on the ETX FAQ page.
Subject:	etx 125ec meade telescope
Sent:	Saturday, January 29, 2011 13:45:29
From: (
the knobs on the back that control the mirror to view from the eyepeice
to the photo port is not working. When you turn the knob it spins all
the way around. Can I take the back off by removing the 3 small allen
head screws. Hope you can help. Best Reguards,Mike
Mike here: First, have you confirmed that the setscrews on both knobs are tight? Check the "Flip Mirror Repair" articles on the Helpful Information: Telescope Tech Tips page if you need to go further than the setscrews.


Thanks for the tip mike.  I found one fix that was gluing the metal
shaft to the mirror bracket. Instead I removed the screws and I was able
to remove the plastic housing exposing the mirror. I found that one side
of the shaft was flat and the mirror housing bracket was cracked
allowing the shaft to spin. I glued it put it back together and it works
just fine. The glue I used is loctite super glue for plastic.

Best Reguards.Mike

Subject:	ETX70 rear screws
Sent:	Friday, January 28, 2011 20:33:54
From: (
I have constructed a very lightweight electrical focus device for my
ETX70 utilizing a subminiature RC servo converted to continuous
rotation.  It will connect to the focus knob via a small toothed belt,
with matching sprockets on both the servo and the focus shaft.  I am now
in a bit of indecision as to how to mount it below the focus knob.  I
considered velcro, but the robotics firm I got the hardware from
recommends around 2.25 inches between shaft centers.  That means I need
to fabricate a lightweight bracket to mount the servo further away from
the focus shaft.  Question is, how would you recommend I do this?  I
thought about removal of the two hex screws above and below the focus
knob, and installing slightly longer ones to hold the bracket in place. 
Problem is, I have absolutely no idea what these screws are holding in
place.  I sure don't want to mess up a perfectly good scope for an
experiment.  Am I in dangerous ground here, or I just should stick with
the velcro and mount the servo center within 1 inch of the focus knob?
Mike here: The article "ETX-70AT Repair Guide" on the Helpful Information: Telescope Tech Tips page may be useful. Meade used to sell a finderscope (#827) for the ETX-70 that used one of the screws at the rear to hold the mounting bracket.


Thanks again for the rapid reply.  I don't think the reference you gave
me adequately addresses the question.  I read every post listed prior to
contacting you, hoping you had the definitive answer.  After getting
your suggestion on the #827 I Googled it, hoping to find a photo of the
bracket, but I didn't have any luck there.  Since it seems you aren't
sure either, I've posted the question on the CN web site, hoping someone
has run into this issue themselves.  I still appreciate greatly your
suggestions and guidance.

By the way, when I get this "experiment" debugged I'll send you some
photos and thoughts on the device.

Subject:	Broken ETX-90EC right OTA support.
Sent:	Friday, January 28, 2011 15:15:08
From:	p f (
Thanks for the great website.  The right OTA support on my scope broke. 
A couple of years ago it cracked where the Dec lock knob screws into it,
but I was able to repair it.  Unfortunately, it recently cracked again
and this time it's a goner.  I called Meade to see if I could order a
replacement and they said they don't supply that kind of part and that I
would have to ship it back to them for repair at a flat rate of $150. 
The scope is over ten years old and I'm not about to sink that kind of
money into it.  This is really disappointing considering the part
pobably only costs a couple of dollars and is easy to replace.  My
question is, do you know of any after market suppliers of Meade parts,
or where I might find a replacement for this broken part?  Any
suggestions would be greatly appreciated.
Paul Fede   
Mike here: There used to be a seller of the Right Tube Adapter but no more. However, you can possibly repair it yourself; see the article "ETX-90EC DEC fix (Right Tube Adapter repair)" on the Helpful Information: Telescope Tech Tips page. If that doesn't help, I don't know if Dr. Clay Sherrod can do it as part of his Supercharge Tune-up Service.


Hey, thanks for the quick response.  Yes I checked out that article.  I
guess I could attempt another do-it-yourself repair.  I really think I'm
going to have to replace that part though.  I could probably get a used
ETX-90EC for less than the $150 Meade wants to repair it.  Or maybe I'll
just get the CG4 mount that I've been meaning to buy and mount the OTA
on that.  I never had the Autostar anyway.  As long as I can continue to
enjoy the sharp optics on that little scope I'll be happy.  Hmm...Looks
like I've got some thinking to do...  :-)
Thanks again,

Subject:	Re: New ETX-125AT AutoStar #497 Handset Random Reboot
Sent:	Friday, January 28, 2011 10:23:58
From:	Richard Clements (
A quick update on this issue -

I did the handbox update and reset, and things seemed to work fine. 
Then recently it started doing the same thing - randomly rebooting.

What I noticed was that it worked fine when it was very cold (15-20F)
but acted up when it was over 30F.  What I found was the socket on the
Celestron PowerTank is very smooth inside, and the plug on the Meade 12V
adapter has some very-tightly sprung and rounded contacts.  The plug was
working its way out of the socket!  Was not bad on the really cold
nights because the metal had contracted sufficiently I guess.  Anyway,
added a strip of the fuzzy half of some Velcro to the plug and all seems
snug now.

An interesting twist...

Thanks again for a great website!

BTW, I would really like to have a flexi-focuser for the -125, but
Scopetronix is no more.  Know any good deals on one?

Mike here: There are several articles on making a "flexible focus cable" on the Helpful Information: Telescope Tech Tips page. It is a pretty simple DIY project.
Subject:	NonTracking ETX 90 EC
Sent:	Thursday, January 27, 2011 09:59:32
From:	Goodman, F&M (
I am ever grateful for your outstanding site.

My problem is that my non-autostar scope has stopped tracking. The scope
does its automatic pre-slew and I can manually slew, in both directions,
but it will not start to track. there is no motor sound, in that mode. I
opened the base, and there are no obstructions and nothing burned, on
the control board. I looked on your site, for any similar issues, and
could not find any.

I appreciate any help/info you can provide.

May you continue enjoying the Tucson skies.
Fred G. Colorado Springs
Mike here: It sounds as though the Alt/Az mode has been selected on the handcontroller. Check the ETX-90EC manual for info on how to set (check) it.


Mike, thank you for your speedy and helpful reply. The mount is tracking
again, although the power-on setting has changed. Now I must use the
paddle, each time, to get into the polar mode(the proper screw is
removed from the paddle). I can live with this.

Now all I have left to do is to fix the erratic DEC slewing (good info
on your site for this). Soon I hope to fully enjoy the scope again.
Here's to clear skies and great viewing/photography. Thanks again.

Yours in the skies-Fred

Subject:	ETX70 Power supply Questions
Sent:	Wednesday, January 26, 2011 10:30:30
From: (
I know you get a lot of traffic concerning power supplies for the ETX70,
but here is one more, just for the sake of clarification.  I have no
desire to "smoke" the telescope, and am looking for a warm fuzzy from
you prior to connection of the DC.  I have to #607 power cord from
Meade, and am measuring 12VDC at the plug.  I also bought the AC/DC
adapter from them, and again I am measuring 12VDC.  Is this going to
cause any short or long term issues with the electronics or motors of
the ETX70, or would you recommend a DC-DC converter to drop the 12VDC
down to 9VDC?  It also appears that nothing is fused.  Would you
recommend fusing (if so what amperage) or is this just
overkill/overconcern on my part?
Thanks, and keep up the superior work and web site.
David Stacy
Mike here: The Meade adapter for the ETX-60/70/80 seen on the Accessories Reviews: Miscellaneous page ( does 12VDC, 1000mA. It is perfectly fine at those ratings. Some people have been known to add a fuse just as a security blanket. It won't hurt to have one although I've never (knock on wood) had a problem with the Meade adapter for the ETX-70.
Subject:	Daytime moon alumination
Sent:	Tuesday, January 25, 2011 19:48:41
From:	Christopher (
I've just got my first telescope - and ETX-90AT and am having a great
time discovering and learning. I have a general question regarding the
moon, which was visible this morning during daylight hours, which is
obviously not unusual. However, the illuminated side of the moon was not
consistent with the sun's location and I was wondering if it was the sun
reflecting off Earth that illuminated the moon. Please advise.
Adelaide, Australia.
Mike here: If you mean you could see the portion of the moon that was not illuminated by direct sunlight, yes, that happens from sunlight reflected from the Earth. It is known as "Earthshine". It is most noticeable when the moon is less than "half-phase" but can be seen during times of the gibbous phase.
Subject:	RE: ETX 105 Motor Drive Failure-Gear Box Fault
Sent:	Monday, January 24, 2011 23:54:32
From:	Paul Ingham (
I received the new gears from Hong Kong and have now rebuilt the ETX 105
and it is all working great, better than ever, took a couple of attempts
with the thread lock, I had to thoroughly clean and roughen up the
threads on both the worm drive and nut with a rotary tool with a steel
wire brush in it (dremmel type tool).

I have taken pictures during disassembly and repair so if you think it
may be useful to others I will write it up and email it over to you.

Kind Regards

Mike here: I'm sure many others would appreciate the disassembly and repair info.
Subject:	Re: Auto Focus problem ETX125PE + A question
Sent:	Monday, January 24, 2011 11:19:57
From:	Rick Revell (
First of all Best Wishes for 2011 to you all (shoulda sent this sooner).
May it be better than 2010. Andrew I hope you are not (nor any of your
family) involved in the dreadful floods down under.

Re that focusser problem you were dead right Dick, has gone away I
presume with the year change, I loaded 43gg (patched) a couple of days
ago to test the theory, didn't load before as the scope wasn't going out
in 2ft of snow and -12C. So I guess now it won't come back until 2020
but keeping the old firmware just in case.

And the Question.

In sorting my firmware I went through and checked what features I wanted
and then produced the rom to save on disc, no messing about then just
load it. Checking the features I noticed the 'Edit Training Values'
patch. My first thought and still is why would I want to edit the
training values (for me it might even be dangerous, smile). Usually what
I do is calibrate the drives and then train them, either if the scope
starts getting goto errors or has not be used for a few weeks due to
weather and usually thats the end of it. So what would I use this
feature for and when. Simply point me in the right direction and I'll
research it, if it is a long answer. I also feel the same about the PEC
facility and have not installed that.

Any advice and guidance would be most welcome

Thanks for your past help guys looks like me sorted for a few years
(fingers crossed)

Best regards

Rick Revell
Mike here: One reason for "editing" the training values is to avoid the need to actually go through the training procedure.


From:	richard seymour (
The "edit training values" was originally going to simply be "display
training values".
(so i could see how "repeatable" i was when i trained (+/-10%)).
But, when creating the patch, it was just as easy to allow editing.
So i did.   (which tells you a lot about human (or at least my) nature)

Since then, it has proved immensely handy when i switch an Autostar from
scope to scope.
I don't have to retrain, i merely have to key in that scope's values.

Having the display available (you don't *have* to "edit" it) also lets
you know if something has *changed* in the gear system when you next do
do a full Train Drives.

have fun


Thanks a lot, also got the reply from Dick direct and the one forwarded
by you. I can now see how useful it could be and not too dangerous for
yours truly, so I will include it with what will be my standard
firmwares which I am organising just now before hopefully getting some
decent conditions, last decent times were around end October (just
before the snow came early).

All the best,


Subject:	ETX-125 carrying case
Sent:	Sunday, January 23, 2011 19:51:34
From:	Juan Martn Ferrari (
Hello, mi name is Juan and I'm from Argentina. I've been reading your
page of accesories (,
and I don't have the original carrying case. Here in Argentina it cost
400 dollars (for me is too much expensive), so I decide to make my "own"

Do you have the measures of the scope exactly the same as the original
case? Because I will have to cut the foam in order to fit the scope in
the bag.

Sorry for my English.

Mike here: See the "Cases" section on the Helpful Information: Telescope Tech Tips page. There are two articles there with dimensions.
Subject:	simple motherboards+chips for servo motors
Sent:	Sunday, January 23, 2011 07:12:40
From: (
I am looking for  minicomputers simpler and cheaper than the Autostar
#497 that Meade has for controlling a telescope for controlling several
servo motors simultaneously

Where can I find something like this?

I found an Arduino circuit board and an A2 controller (circuit) board. I
would assume they both could be programmed in C++

I would appreciate any leads in this direction.
Daniel Kahraman
Mike here: Try your local hobby shop. Perhaps something for RC planes/cars/boats would work for your purposes.
Subject:	Re: ETX lens, lock
Sent:	Friday, January 21, 2011 09:44:58
From:	Max Catterwell (
Via some help on Cloudy Nights I have now reached the stage of having
made a puller and removed the axle and OTA support. I have cleaned the
clutch components but found this wasn't the main problem. I would think
that only five per cent of the total bearing area was in contact. I have
now rubbed all surfaces flat, but suspect this is not the whole story.
The axle was fairly tight in the small outer bearing, but completely
solid in the large inner bearing. Am I correct in thinking that the axle
should be free to move, be it ever so slightly, within the larger
bearing? This would of course mean also that the axle was a separate
unit that pushed through the OTA support and into this bearing, which of
course makes perfect sense. I have a feeling that before I started this
I saw a picture somewhere, where another owner had broken his axle, but
I can't find it now.
Mike here: I've not had a need to disassemble any of my ETXes to that level so can't answer from experience.
Subject:	Thank You
Sent:	Thursday, January 20, 2011 14:18:11
From:	Carl Rhyne (
Many questions which I will explore later, I just want to say Thank you
for you site and the information on it. It seems as if Meade just wants
to sell not care for customers after the sale, I have learned more here
then anywhere else.

Thank you again, 
Carl Rhyne

Subject:	Request for assistance
Sent:	Thursday, January 20, 2011 01:11:43
From:	Steve Wright (
I have purchased a used ETX 125 PE which I have had for a couple of
weeks.  I have a problem with it and I'm hoping you can help.

The problem is that the scope will only turn about 350 degrees on the
base. When I rotate the scope ccw to the hard stop and then rotate cw,
it will not complete a revolution before hitting the hard stop again. 
The motors work fine and the alignment with or without LNT is fine
provided the scope doesn't need to rotate beyond the 350 degrees to
align.  When it does need to go past that point, the motor sounds like
it's working but the scope won't move.

It seems like a problem with the hard stop but as a newbie to telescopes
and etx's etc I don't want to mess and cause a further problem without
some guidance.
All my best
Mike here: First, your message was originally deleted UNREAD as SPAM due to the SPAM-like Subject line. PLEASE read the Electronic Mail Etiquette page linked on the ETX Site home page to avoid this happening in the future. Thanks for understanding.
If the telescope does not rotate nearly twice around on the base, then there is likely some obstruction preventing correct movement. It could be something as simple as some debris or as bad as a wire out of place. You would have to open up the base and check. If the problem is a wire, you don't want to force the rotation as that can cut the wire.
Subject:	ETX Meaning of name?
Sent:	Wednesday, January 19, 2011 07:15:13
From:	Ivar Dahlmann Olsen (
Hi I am amember of the danish Astronomical Societys ETX group.
Does anybody know the meaning of ETX? if there is one.-
Ivar Dahlmann Olsen
Mike here: "Everyone's Telescope".


Thank You so much!

Subject:	Damaged Spur Gear - Autostar
Sent:	Wednesday, January 12, 2011 11:41:18
From: (
My clutches on my Autostar were not engaging. I took apart the housing
and after close examination learned that the teeth on one of the plastic
spur gears was damaged.

Would you know where I could purchase the correct plastic spur gear

Thank you in advance! 

Mike here: See the articles "Replacement Gears source" and "Gearbox Replacement" on the Helpful Information: Telescope Tech Tips page.
Subject:	meade will fix my etx 125 out of warranty!
Sent:	Tuesday, January 11, 2011 18:24:16
From:	Willie
Thank you for your wonderful informative mighty site!

I just wanted to let everyone know that my ETX 125 is being repaired by
Meade out of warranty it is 9 years old .

They asked me to take off the right fork arm knob and tell them if I saw
three holes or a purple plastic cover , I saw three holes meaning the
newer ETX model, and he said they will repair it!

The gearbox in the base is shot.

The little arm with a ring on the end is snapped and the screw holes
holding the gearbox on are cracked.

Its costing $150.00 to check it all out and fix what needs fixing .Plus
they ship it back for $15.00.

It cost me $32.00 to ship via UPS in original box in a another box. with
$300.00 insurance.

It will take 4 to 6 weeks to get it back.

Will update when returned.

P.S. Please leave off my email address if you deem my note worthy of
posting to your fabulous site.

Sincerely ,Willie

Subject:	problems slewing left or right
Sent:	Monday, January 10, 2011 03:25:22
From:	GPM (
i have a Meade ETX 80AT telescope and while it slews up and down it
fails to slew left or right.  Can you please offer any suggestions as to
what is causing the problem and how do I get the base off so that I can
investigate the matter.  I have removed 3 screws hidden under the rubber
feet but still cannot get the base off.  Many Thanks
Mike here: Before opening up the base, do some troubleshooting first. You say the telescope does not slew horizontally. When you attempt to slew, can you hear the drive running? What happens if you increase the slewing speed?


Thanks for getting back in touch
Yes I can hear the drive running and it quickens up if you increase the
slewing speed.  I have took the telescope off the tripod and laid it on
the side and got a slight bit of movement from the base both ways when
pressing the slew arrows but then it stops after about a quarter of a
revolution with the motor running.  it is as though some gears
disengage.  If I put it back on the tripod and hand tighten the two
bolts nothing at all happens, just the motor running.

Many thanks again
Mike here: One last test: with the azimith axis unlocked, can you rotate the telescope by hand without any feeling any resistance in the movement? Does it rotate in both directions? Go slowly and try to go more than twice around.


I have checked as requested and cannot feel any resistance in movement
Mike here: OK. It sounds like one of several things may have happened, all on the gear train. One of the gears could be loose on its shaft, one of the the gear mounts has broken off or become loose, or one of the gears has been stripped. I'd vote for the first or second culprit as the most likely. See the articles "ETX-80 Axis Repair" and "ETX-70AT Repair Guide" on the Helpful Information: Telescope Tech Tips page.


Many many Thanks

Subject:	RE: ETX 105 Motor Drive Failure-Gear Box Fault
Sent:	Saturday, January 8, 2011 10:33:01
From:	Paul Ingham (
Thanks for your swift reply, I will try and find those articles. Not
sure what is up with my scope it just seems to be wrong, I will try and
take some better picture or make a diagram to better explain, I have
cleaned the shaft of the large white gear that drives the worm and
lubricated with lithium white grease but the outside diameter of the
shaft seems to be the same size as the hole in the casing it passes
through so rotation is nearly impossible, there is a shoulder on the
gear with a smaller diameter but that was not the part in the casing, it
just looks wrong to me.

Would you happen to have any pictures of an ETX105 drive so I could
compare, I could not find any the same on the net so far but will keep

Kind Regards
Mike here: All I have is posted on the Tech Tips page.


My model looks to be similar to the one you have here
What I need to know is should the shaft marked in the image below as "A"
be extremely tight in the casing marked "B", when I say extremely tight,
you can only insert the shaft with force using tools. The shaft needs to
rotate in this casing so I don't believe this is correct, I have
stripped this down and cleaned and re-greased, how can this be?

Is the spur gear that got stripped a symptom of this tight shaft problem
or is it really meant to be that tight?
Keep the good work up this site is a wealth of usefull information for
beginners with the ETX like me.
Kind Regards
Mike here: Obviously, the shaft needs to rotate. But it also needs to NOT shift as the telescope is rotated. I've never disassembled that component myself. Perhaps there is a "pinch washer" that is involved that secures the gear shaft.


There are domed washers and a hex nut at the gear end and a 12mm nut at
the other.

Are you saying it possibly may be tight to stop the worm drive giving
the shaft horizontal movement?

I do not understand how it could just become tight but I don't believe
the gearbox should have to fight against such extreme friction to rotate
the worm drive.

When I figure out the solution I will send you a full report in the hope
it may help others. I have contacted to see if they can
advise, I just need to know how tight that shaft should be in the
housing. Somebody out there must know!

Kind Regards
Mike here: The gear shaft has to not move except in rotation. So, it is not surprising it should be secured in some manner. As to what that manner is and why it is preventing the rotation, I don't know. Like you, I await a response.


F.Y.I, from
  The worm shaft is usually fairly tight on the RA gearbox, and
  generally if  a gearbox is going to breakdown due to a binding shaft,
  it would go on the first use. You can adjust the tension on the worm
  shaft itself, but you also need to look at the tension on the main ra
  bearing on the mount as that effects the gearbox too. My opinion is
  that it should be 'firm' but not 'tight' if that makes sense.

Subject:	ETX 105 Motor Drive Failure-Gear Box Fault
Sent:	Saturday, January 8, 2011 04:42:00
From:	Paul Ingham (
My ETX 105 has been in storage for about 12 months and when I switched
it back on I got a Motor Drive Failure message on the Autostar 497 and a
knocking noise from the fork base.

After following your guidelines for stripping down I discovered a
stripped spur gear that I have now ordered at (another tip
from your site) the item number is GC0.5-12/24-20 and is one of the 4
identical gears in the centre of the gearbox.

My question is related to the picture attached. The large white gear
that drives the worm drive seems to be very stiff in the blue casing and
I believe this was the cause of the gear being stripped. Have you got
any guidance on how this section of the gearbox should be re-assembled
and how tight the parts should be.

I was going to sand the white gear spline to make it fit better in the
housing, is this advisable?

There is a step in th spline diameter and it is the largest part of the
spline that passes through the housing is that correct.
Kind Regards
Paul Ingham (UK)


Mike here: There are several gearbox repair articles on the Helpful Information: Telescope Tech Tips page. If the gear does not rotate properly, it could be that some debris is clogging up the movement or that any lubrication has dried out.
Subject: Meade ETX105?
From: Steve Siegel (
Date: January 5, 2011 6:36:10 PM GMT-07:00
You always seem to come through when nobody else can!
I'm looking for a Meade ETX105, preferably with UHC coatings, but I
can't seem to find out if this instrument has been discontinued or is
just out of stock. There's nothing even on Ebay, yet there's tons of
ETX90's and 125's out there.
What gives?
Any help most appreciated!
-Steve Siegel
Allentown, PA
Mike here: The ETX-105PE was discontinued a few years ago.
From: "Djamil B." (
Date: January 5, 2011 2:51:40 PM GMT-07:00
Subject: 10-year old ETX
Greetings Mr Weasner....and Happy new year.

Delighted to see you'still running your website and providing valuable

I got my ETX125 nearly 10 years ago and it has the older 'notoriously'
slippery DEC mechanism (I think). I had it serviced once by Meade and it
did fine for a while, not sure how it runs now.

I recall Dr Clay was doing 'supercharging' a while back. I have a couple
of questions if I may.

   1.How do I assess if the scope needs to be supercharged (any simple tests)
   2. Are there any hardware upgrades available? 
   3. What is minimum needs to run GOTO from a PC with Starry Night?
I have the AutoStar but will most likely need to upgrade the remote
(gonna be tough as my current PC does not have a serial port.
Thanks again,
Mike here: Dr. Clay Sherrod is still doing Supercharge Tune-ups (link to info is on the ETX Site home page). If you know your telescope is mechanically or optically no longer performing up to your expectations, Dr. Clay can set things right. So the tests are to use the telescope, doing GOTOs and a star test. Of course, be certain you have done a CALIBRATE MOTOR and TRAIN DRIVES, and be certain the AutoStar parameters are set correctly. To use any software to control the ETX-90/105/125 you will need a #505 serial cable (easily made; see the Helpful Information: AutoStar Info page) and a RS-232 serial port on your computer. If your computer has only USB, you will need a USB-serial adapter. However, not all adapters work reliably with the AutoStar. I recommend Keyspan. Also, if your AutoStar ROM is not reasonably current, you may want to consider updating it to 4.3Eg.


Thank you very much Mike for the valuable information.

Subject: Meade etx 90 ec
From: Cyril (
Date: January 3, 2011 1:07:16 PM GMT-07:00

My scope has not been used for a year
Stored in its hard case  nice and snug.
Got it out today and replaced the battier's
Slew's' left and right , but not up and down
Can anyone help ???????
Mike here: Does the altitude lock hold the tube in place when locked? If not, it is likely the Right Tube Adapter is broken; see the article "ETX-90EC DEC fix (Right Tube Adapter repair)" on the Helpful Information: Telescope Tech Tips page. If the lock holds, then there is a different problem. Do you have the AutoStar or the standard EC Handcontroller?


Yes the lock holds okay, and I do have auto star and the standard hand
The auto star came up  with motor fault  ????
Mike here: Have you inserted fresh batteries? If not, do that. It may solve the motor fault (or it may not). If it does, do a Calibrate Motor. If it doesn't, see if you can do a Reset on the AutoStar. You may have to hold down the MODE key when you first power on the ETX.

And more:

Yes I did put new batteries in, and I rest it  with no luck,
It seems to only have one slew stop that's going anti clockwise.
Thank you for your patience 
Mike here: So you have a broken azimuth hard stop too? Well, lets solve (if possible) the altitude problem first. Check the HBX cable, connectors, and jacks, although if the problem occurs with both the EC handcontroller and the AutoStar you can rule out the AutoStar as being part of the problem, meaning the problem is on the ETX itself. Look for dirty or bent pins in on the HBX connector and jack. Also, look for pins that are too depressed. One other question: when you try to slew up/down, can you hear the motor running?

And this:

I have listened,and there is no sound from the motor slewing up and down
I also looked at the pins and connecters and they look fine.
Mike here: Not good news. It may well be that the broken hardstop and the motors not running are related (or they may not be). If the telescope rotated horizontally too far due to the missing hardstop, then it is possible that a wire was cut. To determine that you will have to open up the ETX and check. That may require some major surgery. If you want to tackle it, there are many disassembly articles on the Helpful Information: Telescope Tech Tips page. If you don't want to tackle it, contact Meade (who may or may not be willing to repair it).


Thank you for your help and time I would like to try and cure this
Where will I find the disassembly tips page
Mike here: Check the Helpful Information: Telescope Tech Tips page on my ETX Site. Lots of articles there.
Subject: Star Test
From: George Layburn (
Date: January 2, 2011 6:15:35 PM GMT-07:00
Dr. Clay and Mike,

OK I know your both probably going to yell at me that it doesn't count.
But knowing my 7 day forecast just keeps being clouds and light snow, I
needed to have something to put my mind at ease about the collimation on
the ETX-90. I decided to set up at one end of the house a battery
charger that has an LED, and the scope at the other end ~40-50 feet?
Very close no doubt, I put a piece of tape with a pinhole over the LED
and focused in on it.

I like to use the 27mm to get a big picture center it up with the
Microstar II, then put in the Zoom tighten in while always re-centering,
then the 9.7 and it's just a matter of focusing. So I did this I know a
bogus test, but focusing in on the LED, then going off focus in each
direction. I was seeing nice round rings, looked just like what one
would want. I know I still need to wait to do it on a real star outside.

But I have a better gut feeling right now that the collimation will turn
out to be fine, after I relocate that baffle to its correct position.

I will get back after the real star test whenever that might happen.
Hopefully sometime while it is still January?

George Layburn
Mike here: Likely correct.


Sounds like an excellent test to me!

Dr. Clay


I know I read about people putting a ball bearing on a fence post a good
distance other crazy methods. I thought well this can't be anymore
insane than that. Give it a try.
Mike here: Anything that makes a "point source" will work.

And more:

Subject:	Monday Night?
Sent:	Saturday, January 8, 2011 00:49:30
From:	George Layburn (
Monday night could be the clear night I have been waiting for? They have
been saying it will be "clear" on Monday night for days now but when a
weather man says that, it means it won't snow.
Monday night is a good night for it, That's put out the garbage and
recycling night anyway. If I am going to dress up like an astronaut
anyway, put out the garbage and recycling, hit the back yard and do the
star test.
But watch the clouds move in. It has been cloudy every night since I
have had you helping me, I been checking.
I get Monday night do the star test, then I get to fix the baffle
problem and Dr. Clay says give it about a week to completely harden with
the Duco Cement. Not a problem looks like it will be at least a week
before I would ever consider using it again anyway with all the clouds
and light snow, that are predicted after Monday.
I'll let ya know what happens. Just an update.



Good luck....I think that you are going to find that your star tests are
excellent.  Just be sure to allow the telescope to cool down for at
least two hours before your tests, outdoors, and use a 3rd magnitude
(not overly bright) star overhead.  Do NOT turn the focus but slightly
out of focus....too large a Fresnel image tells you absolutely nothing.
Turn until you can see the donut hole clearly and no more.  Keep the out
of focus disk SMALL.

Dr. Clay


Dr Clay,

Do you ever actually sleep? I know your in a different time zone. But I
cant believe the hours I get responses.
Your giving me free advice and I am going to do the star test when it
happens for your personal amusement, I am going to have to take pictures
of this baffle before and after. It's off by quite a bit, yet seems to
have no affect in the end.
I think it's going to be fine, I will see the martians waving back at
me. But that Baffle needs to be fixed just the same.
The star test will be done in the name of science. Then break out the
duco cement and do a surgical repair job, as per your instructions which
I have printed out. Yes, I printed out the emails that describe proper
I do my focus with the prided Microstar II, damned shame that
Scopetronix went out of business, they made cool stuff.
Anyway do either of you keep in touch with whatever his name was that
ran that place? What was his name? I know Mike will know the guy. They
made great accessories.
The last false alarm for a clear night I had the telescope sitting
outside for several hours, DAMNED CLOUDS!!! rolled in.


And this from Dr. Clay:

Mike here: When Scopetronix was bought out it no longer had the same "feel" as when Jordan Blessing WAS Scopetronix. The new company did offer the same accessories, just not the same level of service. But their online store is now offline (or at least, they let their domain name expire). There's more on the sad saga of Scopetronix on the Editorial Page.
Subject: Meade ext 90
From: Jerry Greer (
Date: January 2, 2011 1:44:08 PM GMT-07:00

Just bought a used one, looks to be in fine shape.  I have several
	1.	I have the 494 autostar from an older meade scope....will it
	work with the etx?
	2.	What parts should I clean.........just some recommendations
	3.	Where is the best place to buy a 497 controller if I have to
	purchase one.
Mike here: #494 will NOT work with the ETX-90. Don't do ANY maintenance UNTIL you know SOMETHING is needed. You can find used AutoStars online, however, you may need to update it from a very old version of the ROM. That will require a #505 serial cable (easily made), a RS-232 serial port on your computer (or a reliable USB-serial adapter), and Meade's AutoStar Update application (Windows) or AutoStarX (Mac OS X). Alternatively, use a reliable Meade dealer. Either way, be aware if you get a #497 or a #497EP. There are software differences.
From: Max Catterwell (
Date: January 2, 2011 6:00:29 AM GMT-07:00
Subject: ETX lens, lock
A very happy New Year to you!
I have finally got around to unpacking my 125, and have instantly hit a
problem. I removed the tissue from the OTA and went to unscrew the cap;
having never done this before I wasn't sure what to expect, but realised
before it was too late (?) that I was unscrewing the whole lens unit!! I
wasn't certain about this until I found a picture on the net with the
cap removed. I still haven't been able to remove the cap, but that's
something I can work out. My question is, will this have upset
collimation or done any other damage? I am in a state of exasperation at
the moment. I've been so patient with this, and for this to happen is
just unbelievable. It appears I also have a problem with the altitude
lock not locking; it seems to get tight, but doesn't hold.

A very upset newbie looking for your help and hopefully consolation

Mike here: Usually just screwing the corrector lens housing back on fully will not affect collimation. You can check that by doing a "star test". To get the cover off, wear rubber gloves or use a rubber "jar lid" opener.
If the lock is not locking, it could be that the Right Tube Adapter is broken inside the fork arm. Or it could be the locking mechanism needs fixing. There are many tips on the Helpful Information: Telescope Tech Tips page on this problem.


Very many thanks for your quick reply; at least my mind is slightly more
at rest now. I'll do a star test when I eventually get the beast
I'll have a look for posts on the locking problem.
All the very best

And this:

Yes, I will Mike.
I've had a quick look, via removing the dec lock knob and cover, and I
don't think anything is broken - yet! I've been reading the various
posts on this problem on your site, and have determined that I am going
to remove the OTA and examine the clutch.
This I will hopefully do tomorrow if I'm feeling well enough.
All the best

And more:

I started the strip-down this morning and almost immediately hit
trouble. I was following ETX-125PE Mechanical Assembly Notes on your
site.  What this doesn't say about removing the top plate with finder
is, that after removing the screw the plate must be drawn backwards a
little before lifting. If this is not done, a ridiculously weak tab that
slots into a channel gets broken off! Yes, this is what I've done. This
advice may be on your site somewhere, but if it is it wasn't shouted
loudly. You may want to post this. The next thing I found was that the
allen bolts that secure the OTA are neither Imperial or Metric? I'm
going to have to make one up, which is my next job. I think I may have
gathered that some folks have had these supplied, but all that came with
mine was two small ones.
I'll keep you informed

And more:

If you don't know the answer to this one, can you post it please? I made
an Allen key and have removed the OTA.  What I've found is that,
contrary to what I expected, the black plastic shaft that goes through
the centre of the ball cage won't come out. I've applied a reasonable
amount of force but until I checked with you, didn't want to do more.
Does this normally require to be drifted out out using a wooden dowel
and hammer?

At first sight of the gear wheel it looked OK, almost dry, but with just
a light smearing of black moly grease applied. But on closer inspection
with a torch through a gap to the rear, I can see plenty of grease where
there shouldn't be any! So I really want to remove this tube support arm
to disassemble the clutch and thoroughly clean.

I will be patient and wait for a reply from readers of your site if

All the best
Mike here: Should not need to use force or drill anything out. Site update will be delayed about a week.
Thanks, no I wasn't going to drill just drift with a wooden dowel, which
would be much better than hitting directly with a hammer! I'll be

And more:

Being in a calm frame of mind this morning, I decided to have another
look at my problem. I am now even more concerned! I tried supporting the
fork with my left hand while tapping quite firmly with a plastic mallet
in my right hand. No movement whatsoever! Something is clearly wrong
here inasmuch as this pivot should surely be free to move in this
bearing, so allowing the clutch to operate? Please correct me if I'm
wrong. The only way I can see of removing this is to make up a car type
bearing puller; not what I'd expected to do at all.
Hoping you can help here, because I'm becoming quite depressed about

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