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Last updated: 31 January 2012

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:	Meade ETX-105PE versions
Sent:	Sunday, January 29, 2012 10:49:58
From:	Mark Henthorne (
I know the Meade ETX-105PE was discontinued (2008?), but in looking for
one of these, they all seem to be of the Starry tube variety. Did Meade
ever produce these in a blue tube version, or is the starry tube version
the only one available if looking for the 105PE variant?
Mark Henthorne
Mike here: As I recall, the only models of the ETX-105PE produced had the "fancy" tubes.


Wow! Thanks for such a speedy response. Well, starry tube it will have
to be then.

I know it's been said a thousand times before, but your site is a
reservoir of gems of info for ETX users. Long may it continue.

Kind regards,
Mark Henthorne
(in a place you've likely never heard of, called the Isle of Man)
Mike here: I've heard of the Isle of Man but have never been there.

Subject:	Focus Knob Attachment
Sent:	Saturday, January 28, 2012 08:15:10
From:	Phil G (
Haven't e-mailed you in a while but still check your site daily.

In regard to G. Roman's question what I found very helpful to improve
the focus sensitivity on MY ETX90RA was simply to put a piece of rubber
hose of the correct i.d. on the knob itself. This increased the overall
diameter to about 5/8" to 3/4".

I also have the MicrostarII+ and an aside is I e-mailed with Jordan
years ago to slow it down. Jordan recommended that I replace the
appropriate resistor with one of a slightly higher value. I have my
notes in a box with the original ETX drive board. It's around here

If you would like I can open up my MII+ and find the resistor color
codes for you...

Even though I also have a Celestron N5 I still find the ETX is the
'scope I use the most...

BTW, if someone has a spare front corrector lens for the ETX90RA that
has NOT had the baffle come loose I would buy it from them. I fixed mine
years ago but scratched the mirroring a little...


Phil G.
Mike here: Rubber tubing works fine as a focus aid. And yes, would love to have the MicroStar II+ info. I'm sure there are a lot of MicroStars out there.

Subject:	Focus Knob Attachment
Sent:	Thursday, January 26, 2012 23:26:25
From:	Gannicus Roman (
I just got an EXT125 and noticed you have modified your focus knob.  I
was looking at a photo on your tips on using a compass and was
wondering if you would share what you used to modify the focus knob?
I find I have too much movement when looking at Jupiter and its hard
to focus and I bet you found a way around this with your modification.

I would appreciate it if you could share a little more on this.

THanks so much.

Mike here: There are several focus add-ons discussed on the Helpful Information: Telescope Tech Tips page on the ETX Site. As to which one I use on my ETX-90RA, that would be the no longer available Microstar II+.


Thanks so much for the quick reply.  I am new to astronomy and have
been having issues with alignment.  The local store will help me out
but I'll try a few more times now that I have read all the information
on your great site.

Thanks for doing this for us all, especially us amateurs.
Mike here: You've been busy if you have read ALL the info on my ETX Site.


Not quite all but I am getting there after a few more years.  LOL.
Lots of great stuff here.  It's always nice to find others willing to
help out the less knowledgeable.

Subject:	ETX 125pe with mechanical failure
Sent:	Monday, January 23, 2012 14:00:41
From:	james turner (
My etx 125 pe has come loose from it's forks whilst in storage. The ota
is attached properly on it's mountings, but is not being "held" in
position by the forks, and is obviously unusable. Manually lifting the
ota through it's arc, there is a noticable "bump" in it's progress at
approximately 40 degrees elevation.
Mike here: If you mean that the DEC axis lock is not holding the tube in place, it is likely that the RIght Tube Adapter has failed. Although why it would fail while in storage is not clear, unless the lock was overtightened and the telescope shifted from some movement. You may be able to repair it yourself; see the article "ETX-90EC DEC fix (Right Tube Adapter repair)" on the Helpful Information: Telescope Tech Tips page. Meade does not provide replacement parts, so if you can not repair it, you will have to return it to Meade for repair.

Sent:	Wednesday, January 18, 2012 16:36:57
From:	Vincius (
I'm sorry if I'm being inconvenient, but I'm in trouble. I'll summarize:

I bought a Meade telescope ETX 80 with Autostar to go etc.. But he began
to show a fault: Motor Drive failure! The partially disassembled, open
sides and a part of the base underneath. It moves vertically but not
horizontally rotates ...

Thanks if you can help me.

Thank you,

Paulo Rodrigues

Recife, PE
Mike here: Need more info. When the error first occurred did you try a CALIBRATE MOTOR? Have you replaced the batteries? (remember to do a CALIBRATE MOTOR after replacing the batteries) With the axis unlocked, does the telescope rotate by hand freely without any resistance?


Thanks for responding.

I've tried everything, but motor drive failure appears it aligns with
the 1st star, Sirius, and will rotate horizontally when the error
appears and reiinicia. Well, I already started to dismantle to see if
there's something stuck .. send the photos, I managed to disassemble
without breaking, but the bottom do not know how to open .... I'll just
do something with your help.













Mike here: See the articles "Another ETX-60 Repair Guide" and "ETX-70AT Repair Guide" on the Helpful Information: Telescope Tech Tips page. They may be of use. I hope you followed my advice in the article "Disassembly Procedure" on the Telescope Tech Tips page.


I've read, when you get home, I will closely follow the guide. But I still have two questions:

1) One screw on the bottom that appear plastic, should I remove it using
a key, here in Brazil is called key rod 16, if I remember correctly ..
You twist it towards the right to left?
2) What kind of grease should I use to lubricate? White lube does not
fit right. It would be lithium-based grease?

Again thank you so much!
Mike here: Not certain about the screw. Lithium grease is what is usually recommended. In VERY SMALL amounts.


Screw that I say this is the bottom of the base, he is whitehexagonal
plastic (see photo). I just removed the lower metalscrews that are
hidden beneath the rubber base support. I only have this alternative.
Grab  socket wrench and remove the nylon threaded clamp, sorry may
english is too bad.. Well, I need to know if I put the tool in this
piece of nylon in order to openthe base of the ETX. My photo is



Mike here: As I said, not certain about the screw.

Subject:	Power Supply for ETX
Sent:	Wednesday, January 18, 2012 11:16:18
From:	Jonathan Richardson (
I have an ETX 90 and 125 and would like to use an external power supply
to run them.
Can I use a PC power box that delivers 19v or will this ruin the
electronics in the etx.
Many thanks
Mike here: I would suggest sticking closer to 12 VDC. You'll need 1.5 Amp for reliable operation. For more on power supplies, see the Helpful Information: Telescope Tech Tips page.

Subject:	ETX 90 motor mount repairs
Sent:	Tuesday, January 17, 2012 02:21:45
From:	David Blythe (
My son bought an ETX 90 several years ago - brilliant scope - but the
motor mount gears seem to have developed what seems to be the
traditional problem of 'stripping' and the motor mount sounds dreadful
and won't move...

Return to Meade for repair sounds expensive and time consuming :)

Can you suggest whether he should change to a better mount - if so which?
Should I attemot to repair the gears myself - (I am an aeromodeller of
50 years experience) - if so where are spares available? 
Or another route?

Any help you could give would be very much appreciated


David Blythe
S W Cornwall UK 
Mike here: First, you should visually confirm what the problem is. It could be just a loose gear mount or a broken gear tooth. If you need to repair a gearbox or replace a gear, there are several articles on that, including a replacement gear source, on the Helpful Information: Telescope Tech Tips page.


A prompt and helpful reply - isn't the interweb wonderful :)

I will take it to bits and have a look .... I don't scare easily when it
comes to 'having a go' and 'fettling' :)

I've seen a very helpful pictorial explanation of changing gears on that
tech tips bit .. but just thought I'd ask first before diving in ... you
know - measure twice - cut once :)

Thanks - will let you know what transpires 


Subject:	re: power failure due to faulty 12v adaptor - ETX 125.
Sent:	Monday, January 16, 2012 18:03:03
From:	richard seymour (
IF you're VERY lucky, the "only" damage may have been traces burned off
the power panel's circuit card.

A "generic" schematic for it is here:
(yes, that's an LX90, but the thought's the same)

or (reduced to "first principles") here:
(from the older DS family power panel)

You can check with an ohmmeter to see if there's connectivity between
the battery power pins and the wires leading to the motor cards
(don't forget that an external power supply disconnects the battery, and
simply measuring from the power panel's power socket may not be correct
(without a plug), since there may be switching involved there, too)
Do this ohmmetering WITHOUT any batteries attached/installed!!!

good luck


From:	Mike Morrison-Smith (
Hello Dick.
Thank you for the advice. I have had a look and the power board is
putting out 12V on the red and black wire on the two banks of pins, so i
guess power is going to the two handsets. The pins and connected to the
HBX socket. I do not know where else to look. The handset powers up and
has full functionality, every thing except moving the motors.
I do not know if I said, but this rogue power supply blow up a celestron
ultima 2000 and the fault on that is everything works except the motors
turning when pressing the buttons, but they do whirl when the scope is
switched on each time, I think in some calibration process.
Thanks again.
Mike MS.


Without hearing voltmeter readings, i'm working on the parallel
assumptions that your "killer" power supply either:
(a) was putting out AC, not DC
(b) was reverse-polarized (so the plug was NOT center-positive)
(c) was putting out half-wave power (12 volt pulses 25 times per second, with 0v between)
(d) was putting out FAR too high a voltage (but i doubt that from this note's symptoms)

If we knew what the killer supply was doing, that would help diagnoses.

The "motors spin at power-up" can happen if the signal lines are "open".
Try powering up WITHOUT the Autostar plugged in (expect random bursts of motion).

Wait a sec... do you HAVE an Autostar, or are you testing with the
little hand controller?
(which *does* do a calibration sequence at power-up.  An Autostar does
not (unless it was Reset and is rebooting from that).)
The little hand controller (no character display at all) is properly
called the "EC hand controller", not an "Autostar".

You also wrote: "power is going to the two handsets."
Is that a typo (i.e. should have been "motor cards"), or what?

good luck


Thank you for your continued support.
The power supply has killed two telescopes, the Ultima 2000 motors run
at switch on, not the ETX.
I have the autostar handset, I have swapped the circuit board from the
handset over, I think the power supply may have killed that to. I am
running from a 12v car battery now.
The fault with the power supply was not a or b from above. The supply
does something.
I have switched on the ETX unit without the handset connected and the
dec motor does not run on its own. The RA 4 pin lead is not on the
Kind regards,

And this:

If you open the Autostar, the circuit traces pass from the HBX cable
connector through some in-line filtering inductors (labeled with "L"
numbers printed on the card.
Test each one end-to-end with an ohmmeter.  They should read as zero
ohms (dead short).

In reversed-power incidents, sometimes they'll "blow" (act like a fuse)
and then their resistance climbs to "infinite".
You can bridge a blown one with a scrap of wire (or a fuse if you really
want to get fancy... personally, i believe in putting a 1.5 amp fuse in
the power supply wiring).

The outer two wires of the HBX cable are the power leads.

good luck

Subject:	Request for Assistance
Sent:	Sunday, January 15, 2012 21:24:09
From:	D McDonald (
I live in the uk and have an etx 125 which I've had for a number of
years probably 15. There is a problem with focusing the telescope, when
i turn the knob at the back the mirror will not focus properly i have to
keep turning it back and forward and will not focus. any ideas as to
what the problem could be?

Thank you for your assistance 

Dave Mcdonald 
Mike here: First, PLEASE read the Electronic Mail Etiquette and Submittal Guidelines item on the ETX Site Home Page. Your message was originally deleted UNREAD as SPAM due to the subject line text, as specifically mentioned in the Guidelines. Thanks for understanding.
As to the focus problem, it sounds like the focus shaft has become disconnected from the primary mirror. See the article "Focus Shaft Fix" on the Helpful Information: Telescope Tech Tips page.

Subject:	Meade ETX90EC
Sent:	Sunday, January 15, 2012 00:13:43
From:	Dave (
Hi from Dave Have a Meade ETX90EC wont move scope up turns ok goes down
ok wont move up motor runs no movement side screw knob only seems to get
snug barley holding scopes movement and the Degree scale around bottom
is lose should it be attached to scope so does not turn freely any help
would be great thanks
Mike here: Had a little difficulty reading your email since there was no punctuation, so I hope I interpreted things correctly.
If you have an AutoStar, have you done a CALIBRATE MOTOR and TRAIN DRIVES? The Declination locking knob (on the right fork arm) should not be overtightened. If it has been, it can fail. When you lock the axis with the telescope tube horizontal, does the tube stay put or does it want to fall back downward?
Regarding the scale on the base, see the "Q. The Right Ascension (azimuth) setting circle tape moves, what do I do?" on the ETX FAQ page on my ETX Site.


Hi From Dave sorry not the most literate on writing,and spelling.
will try a better attempt at it,but do appreciate your help what you do
is great,I bought this scope slightly used four times.yes when I
received it in case only snugs up to barley hold scope,wont get tighter
than slightly snug still creeps down.motors run will go down but not
up,if you hold it on its side or slightly down it will move up or at 90
degree it will move up,if you move to far forward and try to go up it
stops,like its to heavy motor running hope you can read it and agin
thanks for help.     
Mike here: It could be that the DEC lock is not providing enough friction. There are several DEC lock articles on the Helpful Information: Telescope Tech Tips page. Check them out, especially the article "DEC lock mod".


I did look at the tear down on your sight were shaft broke last
night,upon further inspection took knob off an plate can see crack on
shaft wree brass incert is,the crack is from their to the keyway slot on
plastic shaft.
Mike here: OK. You might be able to repair the Right Tube Adapter. There's an article on that on the Telescope Tech Tips page.


Thanks for help and your sight

And an update:

Hi Mike from Dave took scope apart,does have crack looks like its shaft
is broke just like pic on your sight.Will contack meade to see if can
get the part, sent in warrenty card did you have any problem in geting
part thanks.
Mike here: Meade no longer provides this part to owners. If the telescope is under warranty, you will have to return it to Meade. You may or may not be able to get one from Telescope Warehouse (link on the Astronomy Links page).

Subject:	power failure due to faulty 12v adaptor - ETX 125.
Sent:	Friday, January 13, 2012 08:18:52
From:	Mike Morrison-Smith (
Thank you for your fantastic site. I have just used it to repair a ETX
125 with a faulty hard stop.
In returning it to its owner here in Saudi Arabia, his own (another) ETX
125 is no longer working and I now know the same shop purchased power
supply that destroyed a Celestron Ultima 2000 before christmas has now
claimed another scope.
I do not know if you can point me in the right direction. The only thing
that works is the LED red light. The handset is dead and the base unit.
Do you know, and given I do not know why this has happened, if there is
an internal fuse that would take the brunt of this power.
I can swap bits between the two ETXs to find if one circuit board is not
working but this could extend the damage. 
I will now use a 12v car battery.
Kind regards,
Mike Morrison-Smith.
Mike here: There is no internal fuse. And yes, faulty external power supplies can toast circuitry. For a replacement circuit board, try Telescope Warehouse (link on the Astronomy Links page).


Thank you for the prompt reply. Yes the site is very useful and it must
be rewarding to be effectively world famous for a chosen hobby.
I will try as you suggest. Do you think it would just be the power
supply board or would the damage have gone to the RA and Dec boards.
The same power supply toasted a Celestron Ultima 2000 I had offered to
clean for the local University here in Riyadh. I reforked it in a LX90
and it is an excellent conversion. Not difficult and it gives GOTO for
so little money, the forks, handset and LNT was 100, about $150 and I
would recommend it to everyone. I assume it was something I had done
rather than a defective supply. You live and learn.
All the best.
Mike here: Hard to say what is damaged. But a visual inspection of the boards might show burnt components or traces.

Subject:	re: LNT Fault in Sweden
Sent:	Thursday, January 12, 2012 14:47:48
From:	Ron (

I get the check mount on my LXD 75.  Olof check and see if your mount is
set to Alt/AZ or Equatorial/polar.  Also check, just for the sake of
checking, if your telescope type is an ETX.  It may have gotten changed
for some odd reason  during everything that has happened.



From:	richard seymour (
The "check mount" message means that the GoTo that the scope wants to
perform will (it thinks) exceed the travel limits that are set in the

You have (at least) two ways around the problem:

Fast: Setup/Reset (enter)(enter)   ...that will return ALL of the
Autostar's settings to their defaults.  Then you would have to tell it
your Model, and try again.
(if it works, you'd then go back and do:
Setup/Telescope/Calibrate Drives
Setup/Telescope/Train Drives
Setup/Telescope/Calibrate Sensors

which would make the subsequent alignments much more accurate.

Slower:  visit
Setup/Telescope/Telescope Model (enter)
Setup/Telescope/Max Elevation (enter)
Setup/Telescope/Min Elev (if it offers  it)

...and verify that the numbers are reasonable.
Max Elevation should be 90 degrees.

good luck

Subject:	Re:Final physical path position for etx125 - FB 1/12/12
Sent:	Thursday, January 12, 2012 10:10:30
From: (
The 'Park Scope' function is described in the the manual for both the
AT and PE versions, which can be downloaded from here:
Here's what it says:
"Park Scope is designed for a telescope that is not moved between observing sessions.
Align the telescope one time, then use this function to park the telescope. Next
time it is powered up, pressing ENTER and the telescope moves to its pre-determined
Park position. Once parked, the screen prompts to turn off power.
Important Note: When the "Park Scope" option is chosen and the display
prompts you to turn off the telescope's power, AutoStar is unable to be
returned to operation without turning the power off and then back on."
The final position for an Alt/Az mounted scope is 0/0 Alt/Az
in other words, level and pointing North. When using Park
in the past, I've noticed an occasional glitch where it is parked
at magnetic north instead of true north. When starting the next
session, Autostar assumes the scope is at true north and the
result is an error in GoTo. I have the PE model so don't know
if the same thing happens with the AT.
Mike Hogan

Subject:	pcircuit board on etx125
Sent:	Wednesday, January 11, 2012 13:23:32
From:	mick potter (
do you know anywhere i can find a diagram on how to remove and replace a
circuit board on an old etx125

it has power (both battery and external) but neither the autostar or
basic hand controller light up or work 

i think the circuit board may be broken but have no idea how or where to
get one or how to replace it 

any sugestions or info would be welcome

thanks in advance 

mick potter in the uk 
(and yes that is my real last name )
and my daughter shares the same birthday as harry potter -irrelavant i
know but imnteresting all the same
Mike here: There are several disassembly articles on the Helpful Information: Telescope Tech Tips page on my ETX Site. As to a replacement board, try Telescope Warehouse (link on the Astronomy Links page).

Subject:	Fwd: hi Mike
Sent:	Tuesday, January 10, 2012 05:17:06
From:	Steven Dang (
been a while since i last emailed you.  

One of the sites that i think might interest you is the recent
introduction of live astro parties online. such as this one on
Phil Plaits - astronomer and the host of the universetoday podcast is running it.
Mike here: Thanks. But a reminder: PLEASE use the email guidelines as discussed on the Electronic Mail Etiquette and Submittal Guidelines page. Your message was originally deleted UNREAD as SPAM due to the subject line. Thanks for understanding.

Subject:	Re: Greetings - LNT fault in Sweden revisited
Sent:	Sunday, January 8, 2012 23:35:31
From:	Olof Neiglick (
Happy new year!

A small but not full progress - Meade Germany is not that bad, they sent
me the right mounting bracket for the replacement LNT and it was easy to
put on the scope. Now, next thing I did was to test the auto-align (with
the latest 43Eg software), this is what happens;

from the HOME position, counterclockwise before power is switched on;

- getting date/time OK
- I push Automatic align
- scope immediately starts to move the tube around up/down
- scope moves around to the "FINDING NORTH" procedure - ca 20 seconds

Now there is a new thing I haven't seen before;

CHECK MOUNT (?) and there is a warning message that it may hit the
stops, press ENter to proceed or Mode to skip

What do I do from here ? I have never seen the CHECK MOUNT before with
the old/original LNT.  I tried once to skip this stage but then it went
down tilt to the full stop and I had to power off.

Suggestions please ?

Best regards

Olof (Sweden)
Mike here: Lets back up a step. Have you done a CALIBRATE MOTOR? Also, does the mount rotate (by hand) nearly twice around horizontally without hitting any obstructions?


Yes, rotates w/o glitches, but I'll try the CALIB MOTORS when I get 
home tonight and get back to u later.  Haven't seen the CHECK MOUNT 
thing before...


Interesting one, the new / replcement LNT did not change a thing, i.e.
after the Auto ALign procedure is started, it goes thru its various
stages of finding north, finding level, finding tilt etc - then comes
the selecting star ..., and after this it immediately starts slewing
downwards into the ground from a level position. Exactly what happened
with the original LNT, I double-checked and entered northern hemisphere
coordinates, clocks is accurate and I even tried with the reverse
Up/Down but no change. Suggestions before I admit myself to the
emergency psychiatric ward ?
Mike here: Have you done a CALIBRATE SENSOR? That's different than the CALIBRATE MOTOR.

Subject:	Final physical path position for etx125
Sent:	Sunday, January 8, 2012 17:56:38
From:	Dee Metzger (
Hello, I have a Meade ETX125 telescope with the optional Autostar
controller.  When browsing through the Autostar menus, I happened across
a "Park Scope" option which does not seem to be documented anywhere (at
least that I've found).  Where should the Etx125 end-up at the end of
this cycle?? (I'm thinking it should be same as for polar alignment but
it seems to end up with the scope at 90 degrees to the forks)
Mike here: Park is a position that is a known position for the startup. It is not the HOME position. On the next startup, there is no alignment required as the previous alignment is used. All that is required is that the tripod be placed in the same position as it was when parked and the telescope not moved on the mount.

Subject:	Solar Filters for ext-70 at
Sent:	Sunday, January 8, 2012 01:47:39
From: (
I would like some help with determining what type of solar filter would
be best for my EXT-70 Iwant to see the Venus transit in June and my
questions are the following:

1. Do I need just the filter on front of my telescope or do I need one
for my I piece or do I need both? also which type of filter should I
use? I am leaning to the one for the front of my telescope. Thank you
for your help

Mike here: NEVER use an eyepiece solar filter by itself. A full aperture solar filter is the only safe one, both for your telescope and your eye. Ideally, the best solar filter will screw on to the ETX-70 lens (in place of the aperture cover). Alternatively, a slip-on filter will work; the best one will have locking bolts to keep the filter from slipping off. If you can't locate either of these for your ETX-70, you can purchase something like the "AstroSolar Safety Film", as discussed on the Accessory Reviews: Filters page and make your own filter.

Subject:	About the 125
Sent:	Tuesday, January 3, 2012 18:25:30
From: (
Are you aware of any design changes in the  etx 125 that makes 
the removal of the RIGHT TUBE ADAPTER, (RTA) different on later models?

I tried to remove mine for a routine inspection.

I removed the OTA as described on your site, but the RTA wouldn't 
budge; the left came out easly.

And another question; What would you suggest as the lowest safe
temperature (F) to 
operate the scope, because of the plastic geartrain?

Mike here: I'm in my observatory right now. I don't recall any reports of a RTA change. As to low temps, see the article on "Cold Weather Performance" on the Helpful Information: Observational Guides & References page.



Subject:	EXT125 Drive failure-solution
Sent:	Tuesday, January 3, 2012 11:34:31
From:	Foust MD, Jack (
Wanted to pass along a suggestion for other ETX users:
Last week my batteries ran down and I shut down for the night. Picked a
new batteries a few days later, but noticed that I could get the scope
to slew properly during alignment. Quickly discovered that Alt Drive was
OK, but Az Drive wasn't working at all. I mean  stone, dead, no noise,
no nothing.
After various attempts at fixing, including taking base apart, checking
wiring, etc., started to feel pretty bad, searched internet for
replacement circuit boards (felt that it was more likely a circuit board
failure than a motor failure), finally decided to check Autostar manual
for diagnostics. Ended up trying the "Calibrate Motor" function in the
Autostar menu. Lo, and behold  the drives worked! Did a "Reset"  and the
thing seems to work like new.
Much better than sending ETX back to the factory. I hope this will be
helpful to others who have a drive failure.
Mike here: Glad that solved it. As noted on the ETX FAQ page, anytime the AutoStar behaves erratically, doing a CALIBRATE MOTOR will usually fix it (asuming it is NOT a hardware problem). Also, anytime you change batteries (or switch to or from an external power source), you should do a CALIBRATE MOTOR to calibrate the AutoStar to the encoder output power level.

Subject:	Hello, MWeasner
Sent:	Sunday, January 1, 2012 14:22:41
From:	Stephen Smith (
I just received an EXT90EC as a gift, and it appears that the drive gears
are fairly bone dry, and I'm in the process of cleaning/lubing.

My question for you:

Where can I find a detailed description of how the alignment/tracking/
optical tracking(?) system works?
I don't see how it could just count motor revolutions, as any play in
the gear system would obviously affect the accuracy.
Yes, there is play in my RA gear system, as the gear box tends to
move a little bit when you change directions, causing a pause in tracking. 
I was hoping that cleaning/lubing and re-mounting the assembly would 
take care of any drag that might be occurring, but I was still wondering 
whether there are sensors on the actual table/forks that tell the computer
the actual position, or is it just motor rotations?

I'm sorry to bother you, but my googling skills have proven in vain.

Thank you so much in advance, and hope this new year is a good one for you.

Steve Smith -
Mike here: The ETX uses optical encoders to count "pulses" as the gears rotate. The TRAIN DRIVES measures the pulses for a given telescope movement. Be certain to do a CALIBRATE MOTOR (which measures the current power output of the encoders) and TRAIN DRIVES (on both axes). For more information on backlash and percentages, see the Helpful Information: AutoStar Info page on my ETX Site.


Thank You Thank You Michael. I'll do that.

Subject:	Re: Meade etx 90 spotting scope
Sent:	Saturday, December 31, 2011 18:49:04
From:	Chuck (
Yes I did, the article I saw used the single arm mount, mine is the
older fork type with DS90 cradle inbetween.  At this point I don't think
I will mess with the conversion sense the 494 system is out of date, I
will just use the DS90 as a motorized spotting scope. I must say
optically the DS90 dosen't compare to the old ETX90 .

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