ETX-90EC USER FEEDBACK
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: email@example.com (Clay Sherrod) To: firstname.lastname@example.org (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 SherrodAnd:
From: email@example.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: firstname.lastname@example.org (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 MikaelAnd some thoughts:
From: email@example.com (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 SherrodAnd some more from Clay:
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 SherrodAnd an update from Mikael:
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 MikaelAnd more from Clay:
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?Mike here: If the DEC (same as Altitude) lock does not fully lock, the tube may not move. But you can tell the lock is not engaged since you'll be able to move the tube in declination by hand very easily. If that's the case you have a failed Right Tube Adapter and should contact Meade for the replacement part. Replacement is easy; see the bottom of my ETX-90EC Comments at: http://www.weasner.com/etx/90ec_comments.html.
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..Mike here: If you don't hear the motor drive then it is definitely not the DEC lock problem. Either the controller is not working or there is a problem inside the ETX. If you have an Autostar, you can try slewing with it. If not, you might check with your dealer (if local) about trying another handcontroller.
Subject: Meade ETX90 Sent: Monday, February 12, 2001 07:24:10 From: firstname.lastname@example.org (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 email@example.comMike here: Nice to hear your positive report. As to magnetic compasses, they can be affected by nearby metal surfaces and/or electrical devices. So, keep them at least three feet away from the ETX for the most precise reading (I typically abuse this in practice however). And you're right about hanging extra weight on the ETX-90. In most situations you will need to counterbalance the weight and if the camera is very heavy, the axis locks may not hold or tracking may be impacted.
Subject: Scope mounting Sent: Saturday, February 10, 2001 21:35:37 From: firstname.lastname@example.org (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. email@example.com writes: > Clay Sherrod (firstname.lastname@example.org) 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, RickMike here: I've never seen a streaking due to motor vibration with either the ETX-90RA or ETX-125EC and I don't recall any when I had the loaner ETX-90EC.
From: email@example.com (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.... ClayMike here: I'm wondering if the vibration suppression pads would help?
I've had the same thought. Any suggestions for a short-term (or long-term, I ain't choosey [g]) alternative? Cheers, RickMike here: Celestron has some tripod vibration suppression pads. And more from 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, RickAnd more:
From: firstname.lastname@example.org (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 (email@example.com) 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 WeasnerAnd:
From: firstname.lastname@example.org (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. ClayAnd more:
From: email@example.com (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 SherrodAnd from Rick:
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, RickAnd more 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, RickAnd from Clay:
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! ClayAnd:
From: firstname.lastname@example.org (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, RickAnd from Clay:
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. ClayAnd more:
From: email@example.com (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. ClayAnd:
From: firstname.lastname@example.org (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, > RickAnd more from 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 HawaiiMike here: I suspect you have a Right Tube Adapter failure. Check the comments at the bottom of my ETX-90EC writeup.
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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