Last updated: 31 December 2006
This page is for user comments and information specific to the ETX PE (Premier Edition). Feedback on the specific PE technologies (Automatic Alignment + SmartFinder, Level North Technology) will be covered here. Feedback on the Autostar Suite AE (Astronomer Edition) will be posted on the regular Autostar Suite feedback page. Items that are applicable to all ETX models (EC, AT, PE) will continue to be posted on the other appropriate feedback 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: Meade ETX90PE Drive Issues and Tuneup Procedure Sent: Sunday, December 31, 2006 14:41:38 From: John Murphy (firstname.lastname@example.org) I've had an ETX-90PE for about a week and have had two decent nights to test it out. Prior to the first outing I had trained the drives, aligned the LNT module, etc. Once I got it aligned to a couple of stars I actually was getting reasonable GOTO results on the first night, although it became readily apparent that the quality of the drive system was weak the backlash in the gear train was frustrating, to say the least. Realignment was required after viewing 3 to 5 objects. After I found your very impressive website I realized that I wasn't alone in my concerns about the Meade electromechanical system. Evidently many contributors have taken it upon themselves to dismantle and adjust their equipment in order to improve the accuracy of the GOTO system. The main question that I have is this: are the shortcomings of the Meade ETX drive system to be expected in any scope in a similar price range? I don't want to ship this unit back to the dealer only to experience similar frustrations with a different brand, but on the other hand, taking a new scope apart just to overcome poor quality issues rubs me the wrong way. If I keep the ETX, is it worth the risk of taking it apart in order to improve its accuracy? I am fairly competent at the tool bench but some of the procedures described on your site seem delicate and somewhat risky. I read through Mr. Sherrod's fine documents on the recommended tune-ups but the link to the Scopetronix site is broken [Mike here: fixed] Is there another page that addresses how to get into the most recent ETX90PE to clean the clutches, gears, etc? Thanks for your great effort on this product. The scope seems to be fine optically it's just the rest of it the leaves me wondering what the Meade engineers were smoking when they designed this thing. Best Regards, John MurphyMike here: First off, doing a CALIBRATE MOTOR and TRAIN DRIVES will go a long ways to improving GOTOs and tracking. Using a high power or reticle eyepiece when training the drives (don't forget to do both axes) on a distant object will result in the best training. If you have done that AND you use a high power (or reticle) eyepiece when centering the alignment stars AND you have the telescope base level then you should get the expected and typical results of good GOTOs and tracking. The better you do these steps the better the payoffs. If you have been less than accurate then the results can be less accurate as well. HOWEVER, doing the steps with a lot of precision can detract from the enjoyment so it becomes a tradeoff in what you want. As to going inside, there are no current PE model instructions for disassembly. And until you absolutely know you MUST go inside, I recommend against doing it.
Subject: ETX-125PE Issues Sent: Monday, December 25, 2006 15:06:41 From: Brian Campbell (email@example.com) Thankyou for your great public service website and thankyou for your seemingly endless patience with dumb emails of which this is surely the dumbest. I have in the last week received the ETX-125PE with the new framed "SMART" finder. I am writing from the UK so forgive my english. Here are my first reports: Out of the box the "SMART" finder was so off that I could not get the finder dot onto any terrestrial object centred in the telescope eyepiece by using the screw adjusters provided. Common sense told me that the finder was mis-mounted so I first tried loosening the finder pedestal mount screws but they were locked to their nuts. I then tried to brute force the point where the finder pedestal(very flimsy) met the curved mounting plate which is screwed to the OTA itself. There is a rubber gasket between the pedestal and curved mounting plate which allows a little movement and this was sufficient to realign the finder to the position where the screw adjusters could centre the image. Yay! success! BOO to Meade for shipping such a misaligned finder in the first place. I then tried a couple of nights observing during a recent batch of cold frosty clear nights that we have had recently in west Wales. Despite all combinations and permutations of alignment techniques, motor calibration,LNT calibration, auto and two star alignment, I was not able to get the scope to consistently GOTO the stars in the handset catalogue without some error greater than the FOV of the standard eyepiece(26mm). Sometimes I had to make massive adjustments, My Lat, Long, timezone and time were right on and I chose the right stars for certain. My immediate feeling was that I had wasted money on this 'scope, but on reading your pages I found I was not alone. Despite repeated motor calibration, motor training, LNT calibration things have not improved. In an effort to reestablish the supremacy of reason I tried another tack. I took the scope into the study and attached a cheap laser pointer to the OTA with blu-tack. I aligned the laser spot to a convenient stain on the wall and switched the scope on. Mode, Mode, Long press Mode etc soon got me to the scope AzAlt 00 00 00 screen. I then tried moving the scope by handcontroller in all directions by hand and successfully got it back home (00 00 00) easily by eye. When I made the wall stain my terrestrial object, I could not automatically return there by GOTO landmark without an error of 1-2 degrees especially in the azimuth direction. (This is an easy test of drive accuracy to do and can be done on cloudy nights indoors and I commend it to your readers. ) There is some azimuth slack ( about 1 degree) clearly demonstrated with the laser pointer and manual stress to the azimuth axis, but much less so with altitude. The question is, do you think it is a mechanical or software error or both. The answer is likely to be both, but I thought you readers should hear about my laser pointer technique for checking mechanical alignment anyway. Merry Christmas 2006 Brian Campbell Aberystwyth Wales UKMike here: There have been similar reports of not returning to a known landmark. However, that can be due to errors in the CALIBRATE MOTOR and/or TRAIN DRIVES. Since there isn't anything you can do with CALIBRATE MOTOR since it is just a set mode in the AutoStar (but doing it is important), the TRAIN DRIVES becomes an important step the accuracy of the slewing and GOTOing. What object did you use and eyepiece did you use for the TRAIN DRIVES and did you do it on BOTH axes (a common new user mistake is to only do one axis)?
Subject: RE: New ETX125PE SmartFinder Problems Sent: Monday, December 18, 2006 17:07:14 From: Susan K. Brubaker (firstname.lastname@example.org) Thanks for taking the time to try to help me. Sorry it's taken me awhile to get back to you guys. Between the holidays, weather, and life, I haven't had the new scope out again and probably won't until after the first of the year. With the neighborhood Christmas lights I wouldn't see anything anyway. To check LST time I used one of several calculators I found on the internet, and yes, I was aware that it was Local Sidereal Time. Meade has never replied to my problem with not enough 'up' travel for the Smartfinder dot. As someone suggested, my next step is to calibrate the sensors. Tracking-wise, it is encouraging that the scope does a good job after automatic alignment. In the meantime, I came across another problem. I bought a case for the scope and it doesn't want to close right. I think it's hitting on the Smartfinder and I suspect it's because the case was designed for the previous version where the Smartfinder screen didn't permanently sit on top of the LNT. Anybody else run into this? I hope to get back to you guys after New Years. In the meantime, have a safe and happy holiday.Mike here: Yes, that can happen with pre-PE model cases. If the case uses foam you should be able to cut out an area for the LNT.
Subject: LNT summary Sent: Friday, December 8, 2006 08:05:28 From: Henrik VAN HOLTHOON (email@example.com) I have looked at your article covering the LNT module. Very interesting I must say. However in my opinion the LNT module has the following sensors; Electronic level Electronic compass These components are not expensive anymore. You state also there is an array of accelerometers incorporated into the LNT ? So my question to you is why do you need accelerometers, an accelerometer measures change in speed dv/dt. I do not understand what would be the function of an accelerometer in the LNT module this in relation to the orientation. The electronic compass does the orientation and the electronic level measures the leveling of the OTA and the tilt of the vertical axis as you can see during the automatic alignment after pointing to north the ETXPE measures the horizontal plane in two directions 90 degrees apart in order to do the leveling and tilt measurement of the horizontal axis. But I did not open the LNT module so you can be right of course. Most regards Henrik
From: firstname.lastname@example.org (email@example.com) Hi Henrik, I'll try to explain my conclusions like this: The LNT does not have an actual electronic compass. It has a sensor that detects when it slews past Magnetic North. When it does, it switches a digital signal off or on. The Autostar detects this signal and saves the position of the drive encoders at that instant. This becomes the North reference. From then on, Autostar uses the drive encoders to determine what direction the scope is pointing. For determining level, The LNT does not use any kind of mechanical level device. It uses the accelerometer array to detect vertical motion with respect to the Earth's gravitational field. As the scope slews up or down, the array tilts with respect to the field so it's acceleration is a vector quantity with both horizontal and vertical components. When it is exactly parallel, there is no horizontal component so that position is saved as level. When determining the Tilt coefficient, the scope slews about 90 degrees in Az while the accelerometer measures any vertical movement.. This allows the tilt of the platform to be calculated by the Autostar. When that part of the Auto Alignment is completed, the Autostar has the encoder position for "0" degrees Alt and Az, and also a correction for any variation of the Alt position as the Az position changes. From that point on, the LNT serves no further purpose. To further refine the positions, Autostar adds a correction for magnetic variation determined from the lat/lon of the observing site, plus corrections measured during the Cal Sensors procedure. All the above is based on my own assumptions and the actual components used in the LNT, which you can see here: http://www.weasner.com/etx/techtips/2005/lnt1.html I hope this is understandable. Regards, Mike Hogan
Subject: New ETX125PE SmartFinder Problems Sent: Saturday, December 2, 2006 09:24:52 From: firstname.lastname@example.org (email@example.com) >Also, I noticed in one of your postings that the LNT is supposed to be >parallel to the tube, which could, of course, be part of the problem. I >think I can tell just by looking that it isn't. The nose is closer to >the tube than the tail. I've only seen pictures of the new Smartfinder configuration, but if the adjustment process is similar to the earlier one, it's only the -LNT cover- that you're looking at. The actual LNTcircuit board is inside the cover and firmly fixed to the mounting bracket. The flimsiness you mention is probably just the movement of the cover against the internal springs that hold the adjusted position. When you adjust the Smartfinder, you're only moving the cover so it may appear to be non-parallel with the tube. The LNT itself doesn't move. I don't think you should wedge anything like a Leggo under it since you could possibly crack the LNT PC board. Mike Hogan
From: Susan K. Brubaker (firstname.lastname@example.org) Thanks guys for taking an interest. I still have not heard back from my email to Meade. Disappointing. I'm using the finder by remembering that it needs to be placed below the target. (I'll probably also attach a Telrad.) As for the guy who can't get his to find or track right, I finally changed my site to 'city' instead of zip code, I also double checked the LST time and it was correct. Now, it doesn't come very close the first finder star, is a little less off the second finder and after that it does real well. I had it track the moon for about 1/2 hour the other night and it found it and stayed right with it. Sometimes I have to do the alignment twice. This was with the two star alignment, not the 'easy' one. The 'home' positions are different. And home position does make a difference apparently.Mike here: It sounds like you need to CALIBRATE SENSOR for the LNT. Select that from the AutoStar and follow the prompts.
What are you using as a reference for "LST time"? I assume you're aware that stands for "Local Sidereal Time", and not Local Standard Time; some folks have confused the two. Do you have another method to calculate Sidereal time for your location? When you set Date and Time in the Setup menu, you need to use the time from the "clock on the wall" without any mental adjustments for Daylight Saving or Time Zone; those settings are made elsewhere. From your description of the problem, it sounds like you have a time offset, especially if your Site location values are fairly accurate. Whether you use Zip Code or City sometimes depends on where you live with respect to a particular city. If you live several miles from the nearest city, Zip Code may be best . Regards, Mike Hogan
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