ETX-90EC USER FEEDBACK Last updated: 28 February 2001

This page is for user comments and information specific to the Meade ETX-90EC. Comments on accessories and feedback items appropriate to other ETX 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:	etx / NexStar test report
Sent:	Sunday, February 25, 2001 04:21:34
From:	sherrodc@ipa.net (Clay Sherrod)
To:	etx-90@pinefields.com (rick etx)
Rick - 
I would like to highly commend you on an EXCELLENT and unbiased review
of your comparisons between the ETX and the Nexstar; you comments are
just, fair, complete and very professionally presented.  I know you have
experienced difficulty and disappointment with your tour of the ETX, but
your objectivity really comes across in this review.

Many of your points are very instructive and certainly reinforce many
aspects (i.e. training of ETX and the alignment precision adjustment for
Nexstar) that are crucial to observer satisfaction and understanding of
their respective telescopes.

Just thought you would like to know that we appreciate a such in depth
and experienced overview of the pros and cons of both scopes.

Clay Sherrod

From:	etx-90@pinefields.com (Autostar Software Review Project)
Thanks.  It's a little too easy for folks to drop into a "us vs. them"
mindset; I thought I'd take a crack at trying to come up with a little
more than a spreadsheet comparison in hopes of combating that.

Cheers,
   Rick

Subject:	ETX 90EC and backlash....
Sent:	Thursday, February 22, 2001 12:14:01
From:	mikaelr@hotmail.com (Mikael R)
must first say that I am admire over how great site you have done.

Now to my problem.. I bought at ETX90EC for 2 weeks ago and have used it
a couple of times. Great images (compared to my previusly 6" f/5 newt)
and good mechanic (when they work).

The thing is that I seem to have great deal of backlash:

Az
#1- 2 min 55sec
#2- 1 min 24sec
#3- 21 sec
#4- 11 sec
#5- 2,5 sec

Alt
#1- (didn't preform a test)
#2- 1 min 40sec
#3- 25 sec
#4- 12 sec
#5- 3 sec

The way I did it was through the Autostar (ver. 21Ek), when initiated I
held down the "MODE" to enter the status display. There I used the
Alt/Az display to see when the digits started to decrease/increase
(=starts to move). Must point out that I used the "Performance
Enhancement - Creating The Perfect "GO TO" ETX or LX 90" guide to tune
up things like the DEC lock, the Autostar, training and home position.

I must point out that I have had better backlash before when using
higher Az/Aly percentage. Then I got something like:

#1- 1 min 50sec
#2- 43,5 sec
#3- 11 sec
#4- 5,5 sec
#5- 1,5 sec

I have read on previous messages that 3-5 sec is too much.. so my 1 min
backlash must be horrible.

I don't belive that there's anything wrong with the unit.. but maby
something I'm doing wrong??

Best regards
Mikael

From:	sherrodc@ipa.net (Clay Sherrod)
This sounds like a clear case of improper motor training.  Please check
the following:

1)  is Autostar set to proper telescope (ETX90)?
2)  is "Mount" on Autostar set to whichever mode you are using (you did
not specify whether this is Alt-Az (which it sounds like) or Polar;
3)  have the motors been calibrated?
4)  was a reset done after the 2.1ek upload and before initialization?
5)  if motors were trained, were they trained using the mount
configuration (i.e, Atl-Az) that you are actually observing in?
6)  if so, at what magnification and with what type of object and how
far away?

The backlash (actually motor response delay) is exhorbitant and this
seems like an improper training session to me; other alternatives might
be slipping smaller gears, but this is unlikely as it is happening in
BOTH axis, and very significantly in both.

Are you operating on DC power, and if so....are you using the internal
batteries?  If so, this could easily be the problem.  Some ETX's (my
-125 included) like to be supercharged.  My telescope mechanical
function and electronic accuracy improved tremendously when powering at
16.3-16.8 volts (it varies) out of the Meade AC/DC inverter.  With the
internal batteries, the symptoms are almost identical to Mikael's ETX
90.

I very much believe that all ETX scopes operate more efficiently between
15 and 18 volts, far more than the 12V output of the internal batteries
or most battery packs.

So...I would say:  1) poor training is likely; and/or 2) insufficient
voltage to telescope/Autostar.

Clay Sherrod

I think you have your answer.  Your training appears to be the factor,
and believe me it is a cery critical factor, indeed.  You indicated you
followed my Guide, and I am very proud that you did....sounds like you
did a great job.  EXCEPT FOR ONE THING:

If a very distant point source (i.e., a radio tower at 10 miles with a
flashing beacon) is NOT visible for you to do and Alt-Az training on,
you MUST use the bright star Polaris. (See the Guide, Part 2 "Training
in Alt-Azimuth Mode", Figure 3-A.  Read the reasons WHY Polaris is
preferred, among them, 1)gives you the altitude to torque the drive
system; 2) point source; 3) distant; 4) does not move; 5) can use high
power.

I hope you have a higher power eyepiece, because TRAINING must be done
with high power; the higher the magnification, the more careful you are
recentering during training and the choice of your target are the three
critical keys to good training.

Training reduces backlash, which you have plenty of.  Using an object
only 150 meters distant at low power will not do the job.  Training is
the telescope's ONLY chance to communicate to the AutoStar what kind of
backlash it has in the gears; during that communication, AutoStar
accepts that information and tucks it away in memory to assist the
telescope once training is done.  It essentially says back to the scope:
 "you told me that your backlash in Azimuth was very bad, but don't
worry, I'm going to send out signals aso that Mikael will never know!"

Please retrain per the detailed instructions in the "Enhancement Guide"
Part 3.  RESET your autostar prior to training and be sure to check your
scope and mount specs BEFORE doing the retraining.  DO NOT use the
telescope motors for"testing" or any such thing after RESET and until
you can get the training done....I do not even use my motors to align to
Polaris or my target; I do that by hand, leaving my motors unturned
until the training exercise.

Thanks for letting me know...I thought your training was probably off
and I am sure of it now.  Keep referring to my "Guide".....you followed
the book, you just merely skipped over a chapter!  Good luck and good
skies!

Clay Sherrod

Yesterday I did a training on the polaris and I would like to give you a
small report of what happened.

1. I reseted Autostar, entered the usual data (location, telescope etc)
and entered the percentage, Az=15% Alt=10% (must admit that I don't
really recall if I did the calibration before or after I set the
percentage, does it matter??).

2. I went out (-13 C) and placed the scope on a table and used a leveler
to make sure that it was somewhat level to the horizont. I then moved
the scope by hand so it was pointed at polaris. I then had to use the
motors to center polaris in the scope (used magn 310x). Here I stumbeld
on my first problem. I coulden't actually see the contour of the eyepice
so it was hard to say if polaris was really in the middle of the eyepice
or near a corner. But I put the polaris as near the "center" I could.

3. I started the training, first in Az, then in Alt. Used the "2" speed.
And here I had the same problem as before because I coulden't really see
if polaris was in the middle when I stoped it, but I did my best.

4. When I was done I wanted to try the GoTo and began the Aligment -
without leveling the tube first!! So it was still pointed at polaris!!!
So It started to slew, stoped at a point there I coulden't see a bright
star (because the scope thought it was leveled when I started the
aligment, but actually it was pointing at polaris (59 deg!!)) so I just
presed ENTER, and then It continued to slew to the next star, but this
time it went VERY high (+90 deg), so it hit the hardstop and I could
hear how the motor tryed to go beyond that point, but only for a second
or 2. I don't think that anything broke (didn't hear any gear hopping or
anything destructive). I slaped my head by being so stupid! ;)

5. I did a correct Aligment (Easy, 2 stars), but one of the stars was
behinde the house so I just pressed ENTER. When the aligment was done I
pressed GOTO on Venus. Well, venus didn't show up in the eyepice but in
the finder. Tryed the same on Jupiter/Saturn and got the same result,
not in eyepice but in the finder. Made a SYNC on Saturn, and to my
suprise it DIDN'T jump back to its original position! I tried the same
on Jupiter and with same effect! The Rubber banding was like gone! But I
want to test this a little more, but not untill the temperarure rises
atleast over 0 C ;)

Now, in the morning I did a "backlash test" and here's the resault:

Az
#2- 52 sec
#3- 13 sec
#4- 6,5 sec
#5- 2 sec

Alt
#2- 1 min
#3- 15 sec
#4- 7,5 sec
#5- 2 sec

As you see I still got some backlash. The question Is if this is OK for
the ETX or did the hardstop scenario destroy my training, my calibration
at the beginning or even the centering problem?

Mayby I'll retrain the scope again, but with higher Az/Alt percentage and
maby lover magnification and cut the lights out so that I can see the
eyepiece contour so I really get the star in the center.

Thanks for all help!

Best Regards
Mikael

I think we've found your problem, and it may not be your scope....I
THINK your delay is not backlash....but EXTREME COLD.

We're getting there.  First, DON'T lower the magnification for training
and alignment; only for GO TO.  Hitting the hard stop DID NOT do any
damage (the clutch will intentionally slip for a while - how long before
you stopped it??) but I would certainly:  1) re-calibrate; 2) reset; 3)
retrain again.

First, by you moving directly from the training (Polaris) into an
alignment mode and hitting the stop you may have allowed the sensors to
become confused a bit with the optical decoders in each axis;  certainly
your GO TO and Saturn and Jupiter sound pretty good (field of finder
view is typical) but we can get you closer.  WHEN YOU align and set your
telescope to Home Position, it is a good idea to spot Polaris in the
scope first and THEN drop it down to level WITHOUT moving the AZIMUTH
axis; this gives you a precise NORTH orientation that can't be beat.

Your delay times are an improvement;  I would not change the % in
Altitude right now, only go up about 7% more in Azimuth (this might
improve the delay in both); if that is too jerky, come down by 2%, and
so on.  If your Azimuth continues to delay, go up another 5% and see
what happens.

Your training is critical; I think you were okay not seeing the
periphery of the high powered field of view; just get it as close to
center as possible....to closer the better, because training DOES NOT
offset the position of the telescope very much at all.

Overall, your GO TO and your delay times are looking better, but we can
get them better.  Two keywords:  1) TRAINING; and 2) AZIMUTH %

ALSO....you may have hit on a key without knowing it.  At -13 degrees
below 0, your telescope is NOT going to behave normally;  this could
very well be a BIG part of your delay, from the grease within the drive
gears becoming very viscous from the cold.  Eventually you will want to
change out (clean) that gooey stuff and replace with some good white
Lithium grease which is NOT temperature sensitive.

I believe a LOT of your problems in the delay factors and what you are
calling backlash are, indeed COLD-INDUCED resistance of the mechanical
drives of the telescope.  I'll bet you performance (as careful as you
have been) will go up dramatically when the weather warms.  Please keep
me up-to-date!

Clay Sherrod.

Subject:	ETX-90ec
Sent:	Tuesday, February 20, 2001 23:10:37
From:	MrPhatOne@aol.com
I have a question about the ETX-90ec......      Im not familiar with the
electric controller and seem to be having a problem with its functions. 
The telescope moves left and right, but not up or down......     any
suggestions?

And more:

I read your article on your site and noticed that your scope seemed to
be moving down even after you tightened the dec lock...   my system
doesnt even make a sound when I push the up and down arrow on the
electronic computer..   its as if I put it on some sort of disable
mode..

Subject:	Meade ETX90
Sent:	Monday, February 12, 2001 07:24:10
From:	somac@mstore.som.hw.ac.uk (Andrew Christie)
Many thanks for you very helpful site. As a new Meade EXT90 owner I
found it very comforting!

I may have been lucky but I was pretty successful in using the Autostar
from the second attempt on - the first was before reading your site and
is best glossed over. Now everything is pretty well central in the
finder and most times visible in the scope with only minor adjustment.
As you say the key is to get the entire scope level - the rest can be
approximate and the computer can adjust for any variation easily.

A couple of comments/questions:

I now can spot polaris quickly and use it for home alignment - when I
was using a magnet though I noticed some inconsistent readings when it
was anywhere near the scope - is it possible that the drive motor
mechanism contains magnetised material that could distort readings from
a magnet? If so this doesn't seem to be highlighted anywhere.

I have the necessary bits to attach a 35mm camera to the scope. Although
this is clearly catered for in the design I am a bit worried about the
effect on the balance of the scope and any possible damage to the
motors. I am also reluctant to tighten the 2 motor engagement levers too
much but assume that the extra weight of the camera will require some
additional pressure to avoid the clutch slipping.

Any advice would be most welcome.

Some clear nights here in Scotland and given me an excellent start to my
new hobby of astronomy and your website has made it more enjoyable more
quickly.

Many thanks

Andrew Christie
ajc@christie.demon.co.uk

Subject:	Scope mounting
Sent:	Saturday, February 10, 2001 21:35:37
From:	etx-90@pinefields.com (Autostar Software Review Project)
I agree no vibration is a good thing.  Most of the time I don't see it
either, but the other night, while looking at M42, there was a marked 
NE / SW blurred streak instead a fixed star disks.  And this was during
normal tracking.  Not Good.  I also saw this while using the scope in
equitorial mode previously.

etx@me.com writes:
 > Clay Sherrod (sherrodc@ipa.net) said on 2/10/2001 07:48:
 > 
 > >1)  Tracking motors/centering slewing or correcting slewing - the motors
 > >induce NO vibration whatsoever (in Polar mode on Heavy Duty tripod) while
 > >tracking; I have looked carefully for them, but none.  With
 > >slewing/centering at rates UP TO "5" on Autostar, the motors STILL DO NOT
 > >induce vibrations into the optical system, even at 256x!
 > >
 > Good
 > 
 > >2)  Electric focuser - I have the Meade electric focuser on my ETX 125 which
 > >DOES introduce significant vibrations at high power.  We all know that the
 > >Meade focuser is significantly too fast, even in slow "1-2" settings (there
 > >really is NO difference in that than in "5").  the vibrations are very rapid
 > >and short wave and quickly dissipate.
 > 
 > Bad.  The only slight problem I see with the JMI focuser on the -90 is 
 > the VERY SMALL image shift when focus direction is changed.  With the 
 > focuser the change seems more abrupt than would occur by hand so the 
 > shift is noticeable.

Mirror shift has always been pronounced on my ETX.  The only fix I've
come up with, if I go too far in one direction, is to continue well past
that point in the same direction and then come back towards focus.  So,
if pressing the down key takes me past the sharpest focus, I continue to
push the down key to get well out of focus and then try to come back
with the up key.  When I get close, it's blip, blip, blip.  I'm not
aware of significant image blurring from the focuser while I'm blipping
along.

Cheers,
   Rick

And this:

From:	sherrodc@ipa.net (Clay Sherrod)
Rick- actually, what you describe is indeed NOT good; if your motors are
causing that much vibration you may have something amiss beside simply
motor noise.  How do you have your telescope mounted?  Have you taken
off the rubber feet and if not, are they in direct contact with the
mounting surface? (they should not be; it is the main source of fine
vibrations).  Is your scope tight when locked, and check the balance for
me....the OTA should be "loaded," usually with the front end heavier
than the rear; this is difficult to check on an ETX 90 as they are quite
tight anyway, but you should be able to "feel" as you manually move the
telescope.

Putting some type of offsetting torque to one end or the other usually
helps greatly dampen vibrations; in the ETX motor system, "perfect"
balance is a detriment to many mechanical functions.

Let me know....
Clay

And more:

I've had the same thought.  Any suggestions for a short-term (or
long-term, I ain't choosey [g]) alternative?

Cheers,
   Rick

I have the Meade Deluxe tripod and I use it as an alt-az mount (aside
from brief experiments with the equitorial mount).  I keep the
adjustment screws and clamps snugged down.  The tripod is usually set on
my front walk (cement).  The scope sits on top of the head's mounting
plate and the two (stock) mounting screws are also snugged down.  If I
back off the alt clamp, the scope drops the front (like a rock!) even
though I have both the 8x25 right angle finder and a ScopeTronix dot
sight.  Even with the big 40mm ScopeTronix EP, the front drops.  I also
have a dew shield (the blue thingie with a rather painful star chart
wannabe on it - a choice made by the previous owner, *not* me!) which I
run out as far as possible (to control street light glare as much as
anything).

I responded to most of this but, before I forget, I'd sure like to see
the focuser's "FINE" rate significantly reduced, too.  "Blipping and
checking" works fairly well but being able to put the motor in "compound
low" or "low low" would be a welcome tweak.

Cheers,
   Rick

From:	sherrodc@ipa.net (Clay Sherrod)
Mike and Rick -
When I was using the Deluxe #883 even with the ETX 125, my vibrations
were not that severe unless I intentionally made them that way to test;
any were quick to dampen.  As a matter of fact, even setting my scope up
alt-az on its rubber feet on my patio table the first few times I used
it, the vibrations were minimal, except when I walked heavily.

I repeat that I have NEVER at any power seen vibrations from the
tracking motors in either Polar or Alt-Az, and actually none when
observing to centering on medium to slow slewing either, in both modes.

As small as these motors are, and with the differential materials (i.e.,
plastic, brass, steel, to plastic combinations) vibrations must be
coming from something other than the motor, such as something that might
be loose and resonating the motor frequency.

Clay
-----Original Message-----
>Clay Sherrod (sherrodc@ipa.net) said on 2/11/2001 10:57:
>
>>I still do not know exactly what setup Rick is
>>using to get the vibrations...
>
>I've found (with the Deluxe Field Tripod) that hand-induced vibrations
>are smaller and dampen out faster when on a soft surface (dirt, grass) vs
>my concrete patio.  But even on concrete I've not seen severe
>motor-induced vibrations.
>
>Mike Weasner

From:	sherrodc@ipa.net (Clay Sherrod)
Hi Rick -
Wanted to let you know that the front-heaviness is what you want with
the ETX; glad to hear you have it.  The vibrations are still curious and
I have just addressed in another note.

Let me know if you have more info.
Clay

From:	sherrodc@ipa.net (Clay Sherrod)
Rick -
Yes....there is an alternative to the vibration suppression pads and it
is right in you bathroom!  Take three hand towels and fold them twice
(one half fold each time) until you make a small rectangle and insert
one folded towel under each tripod leg.

(this quick fix is for use on concrete only)

You'll be amazed at the difference!  Try it.

Clay Sherrod

Yes.  Basically, with my ETX-90 in alt-az mode, its performance varies
from very good to extremely annoying and barely usable.  There seems to
be no clear pattern to when things will work and when they'll bite the
dust with rubber-banding and so on.  Aside from determining that the
"snap" slew rate is always whatever the initial manual slew rate was,
I've found very little that I can predict about these problems. The
image "buzz" seems to be a function of where the tripod is and, although
I might want some more damping built into the system, there are
workarounds.

Aiming to the level of "always in main EP" still escapes me in any mode.
Tonight anything away from about due north to ENE was anywhere from 1/4
to 1/3 of the FOV of the finder and consistently centered in RA but low
in dec.  In alt-az, it's varied all over the FOV.  I think I'm fairly
careful about alignments, generally accurate with star identification,
and otherwise reasonably dilligent with setup but I have never had an
entire session on objects being somewhere in the main FOV.

Borrowing from Walter Cronkite, "And that's the way it is, February 11,
2001".

Cheers,
   Rick

I think the real culprit is the spreader arrangement which really
doesn't do a lot except provide a place to put the EP tray (see comment
below).  There isn't anything to positively positon the legs except the
hinges at the top.  The struts that hold the tray don't have a positive,
tight fit to the legs (nor, I suspect, were they designed to - this
isn't poor workmanship but a questionable design or budget call).  I
think the LX-90/200 tripod, OTOH, has a fairly rigid plate the draws up,
near the apex or head, against the legs and draws agains the struts
further down.  Something similar with the #899 tripod might help here,
too.

I'll try setting about 10-15 lbs on the tray to see if that calms
anything down.

Cheers,
   Rick

Rick - the spreader "bars" on the #883 are for nothing more than to keep
the legs from separating apart and falling to the ground; you are right,
there is not inner-leg support whatsoever;  I never keep my eyepieces
out, really. I usually keep them in their covers and in my covered
accessory case when not in use (they are too expensive).  Keeping in
pocket is a good idea for cold months.

Your idea of putting a weight on the tray is excellent; I can tell you
right now it will make a considerable difference; however, make sure
that the rolled "clips" which attach the spreader arms to each leg are
fully engaged to the receiver on the leg; they are prone to detach and
if so, they can send your tripod - and so the scope too - into a tail
spin.  It's happened before!
Clay

From:	etx-90@pinefields.com (Autostar Software Review Project)
Geoff came up with another idea that I like, although I haven't tested
it.  In place of the $50 Celestron pads, how about the carpet protectors
for chairs - the ones with the cup for the bottom of the chair leg on
the top and a bunch of pointy spikes on the bottom.  I'll check this out
tomorrow.

Cheers,
   Rick

Rick-  I think the upper part (that holding the end of the tripod leg)
would be too slippery and unstable.  Remember that those protectors
always have a slightly CURVED surface which may just add to your
problem.
Clay

From:	sherrodc@ipa.net (Clay Sherrod)
Rick -I have thought about re-doing the struts on my #883 tripod for the
ETX 90 many times;  they are essentially worthless as you point out.
Nonetheless, as it studied it, it really came down to the fact that the
tripod is SO LIGHT, heavier and even more firm struts would make little
difference; only if there is a really direct (heavy) center of mass on
it would it matter; that is why yesterday I thought you idea of adding
weight to the center tray was a good idea, and still do;  in other
words, if you are going to replace them with , say 1/4" x 1-1/2"aluminum
bar cut to fit (which is what I recommend), I think you should the same
time replace the tray with a substantial (in terms of adding 7-10 pounds
in the middle) metal tray as well.

Clay

From:	sherrodc@ipa.net (Clay Sherrod)
Rick - perfect.  Put a good coat of flat black EPOXY paint on the
plywood and then a coat of flat polyurethane and you're got a winner!
Clay
-----Original Message-----
>Hmmm... looking at the struts, there are slotted holes about midway
>along each strut's length.  Make up a wooden tray, bolt it down at
>those holes and in the middle... and some weight... Hmmm... might just
>be a winner for the cost of a bit of plywood.  How's that sound?
>
>Cheers,
>   Rick

Well, now...  I put 5 lbs of lead shot on the accessory tray and it made
a world of difference.  The scope still rings if it's hit hard enough
(e.g., bumping the tripod to get Polaris aligned) but a lot of the low
level "noise" motion is very much history.  I tried the carpet thingies
again and... eh.  Any contribution to quieting things is hard to detect.

I looked around for a ready-made tray to adapt to the the struts but
came up empty (or unwilling to pay $25-30 for a hunk of oak).  I'll keep
looking because the 5 lbs of lead definitely bent the center plate that
accessory tray fastens to.

Seeing tonight was mediocre with Sirius twinkling away as I set up
around 1845 EST.  The air calmed down in the course of the 90 minutes I
was out.  Unfortunately a layer of haze started in from the east; we're
due for rain later tonight.

Cheers,
   Rick

Subject:	 Alt lock stripping!!!
Sent:	Tuesday, February 6, 2001 10:05:20
From:	Marc.Bernson@hickam.af.mil (Bernson Marc Capt 15 MDOS/SGOME)
Hello and thank you for providing such a wonderful medium to
praise/kvetch over the ETX's. I've had mine since Dec '00 and have not
been able to get the most from it mostly secondary to an expanding
family!  The newest problem I'm experiancing is the knob to lock dec has
stripped and won't hold a lock. I dont feel I had been turning it
tighter then normal torque of say closing a jar but last night it just
spun on the metal nub and I finally just took it off and used a pliers
to tighten/loosen it. I don't remember this problem noted and searched
the archives without finding a similar complaint.  Has anyone else
experianced this and is super-glue my only option?

Marc Bernson in Hawaii 

And:

I called Meade and am waiting for replacement, thanks a million and if
you return to Hawaii anytime soon I'd be happy to show you my favorite
sites...both for stargazing and surfing!
Thanks again, Marc.

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