Last updated: 31 August 2002
Subject: ETX90 Declination motor problem and solution Sent: Saturday, August 31, 2002 16:29:45 From: firstname.lastname@example.org (Dale Gaudier) Great site. I've gleaned a lot of good info on the ETX90 over the past few years. I thought I'd share my experience with a recent problem with the dec motor of my scope, and the cure. I haven't seen this particular problem reported before. The symptoms: my ETX90 developed frequent "motor failures" (as reported on the Autostar) with the unit failing to initialize. It would also sometimes have a runaway dec motor. Shutting down and restarting worked sometimes, but usually only for a short period, then the dec motor would fail or go into runaway mode. I opened up the fork arm with the dec motor using the instructions on the Scopetronix site (thanks Scopetronix!). I took the dec motor unit and electronics board out. Immediately saw that the original Meade grease had gotten onto the phototransistor next to the optical encoder wheel - not good. So cleaned off the glop, along with a lot of other excess grease in the drive train. Cleaned everything up, added a bit of clean lithium grease, then reassembled everything. I did a reset, calibrate motors, then an Easy Align just to check everything out. Everything worked fine for about 10 minutes until I tried to move the scope in declination and nothing happened. Power off, power on, and got a motor unit failure. Disassembled the dec motor unit again. This time I used the regular (non-Autostar) hand controller just to be sure it wasn't an Autostar problem. I tried running the dec motor while it was out of the fork arm. It would run OK when horizontal (PC board parallel to the base of the ETX) but it would stop when I rotated the drive/PC board vertically, as it would normally be in the ETX fork arm. Hmmm. This implied a loose connection, so I got out my trusty soldering iron and resoldered all the wire connections to/from the PC board and dec motor. Ran the dec motor again with the same results - OK when horizontal, dead when vertical. Hmmm. Must be a loose component. I look at all the components. All the surface mount chips look OK. I try wiggling the other components one by one. Aha! the quartz crystal (used for timing) is loose! Further inspection under a magnifying glass shows two "cold" solder joints where the crystal is mounted to the PC board. Looks like the solder was making only occasional contact with the conductors on the PC board - this explains the positional sensitivity of the dec drive unit. The cold joints may have slowly worked their way loose in the two years I've had the scope - this could have been caused by thermal cycling from the scope being moved outdoors for viewing then back inside my house. I soldered the two leads of the crystal, then reassembled everything. Powered up and bingo! - everything works. I've been running the scope each evening now for a week and there have been no more failures. I hope my experience will help someone else out there who might experience a similar problem. Clear skies, Dale
Subject: Mount suitability Sent: Friday, August 30, 2002 13:06:40 From: email@example.com (Brian MacDonald) Great site. Do you know if it is possible to mount an older ETX "M" tube in the mount of a ETX 60? It would allow the use of the Autostar drive with the larger aperature of the 90. Thanks for you time. Brian MacDonaldMike here: Don't think this will work without a lot of modifications.
Subject: Eyepieces and Deep Sky Objects Sent: Monday, August 26, 2002 07:21:19 From: firstname.lastname@example.org (Louai Al Falahi) i have now an 26mm eyepiec + 9.7mm + 2Xbarlow lens and the etx90 ec, so can i see the deep sky objects whith my etx90 and the eyepieces? thanksMike here: Yes and No. You'll be able to see some (assuming dark skies) but not others (beyond the limits of your eye plus the ETX-90). Some will be faint fuzzy blobs and not magnify well. Generally speaking, use the lowest magnification to locate the object and then try increasing it; at some point it will probably become invisible to your eye.
Subject: etx90ra Sent: Sunday, August 25, 2002 21:50:59 From: Dwa644@cs.com just wanted to let everyone know that woodland hills camera is selling brand new etx 90ras for 189.00 that includes shipping. they still have some ones left that come with the series 4000 26 eyepiece. this is a great buy. wadeAnd:
Sent: Tuesday, August 27, 2002 20:35:06 From: Dwa644@cs.com the deal just got better they now are selling the etx90ra for $179.00 and that includes shipping what a deal. wade
Subject: wow! great site Sent: Saturday, August 17, 2002 1:10:10 From: email@example.com (Alexander Duerloo) i enjoyed to visit your site. I hope you know sky and telescope magazine wrote an article about your site. so thats how I discovered your site. I own an ETX-90RA and which one do you own. dont have much expierience with the etx because I own my scope for a month i bought if in mid july and I'm happy I have it now.but thanks to your site it will be lots easier to use my ETX. I have a question for you, my worm wheels are not really correctly set so do you know a trick to re-adjust them correctly? Alexander Duerloo Alexduerloo@hotmail.comMike here: I get Sky and Telescope (have for 40 years!) so I know about the writeup. I currently have the original ETX (now known as the ETX-90RA), an ETX-125EC, and an ETX-70AT. I also still have my 1960s Edmund Scientific 3" reflector (my first telescope). The ETX-90RA is my most used telescope, with the ETX-125EC coming in 2nd. As to worm gears, can you be a little more explicit? There are several articles on the Telescope Tech Tips page that might be applicable.
Subject: A Couple of '90 RA' Questions Sent: Thursday, August 15, 2002 7:18:43 From: firstname.lastname@example.org (Dioni Miranda) Just a couple of questions: 1) Does the ETX-90 RA have hard stops, or do I need to keep track of 'turns' in order not to damage any wiring inside the base? 2) I just got a Celestron red dot pointer for the 90 RA. If I mount it on the plastic towards the back of the OTA (on the RIGHT side of the eyepiece), it gets in the way of: a) handling (comfortably) the screw that secures the eyepiece, b) the declination lock (as the OTA moves up and down), and c) adjusting the hand screw that lies under the red dot find (toward the back) because of all the crowding around it in general. Two questions: I'd like to move the red dot finder to the blue aluminum further to the front, will double-sided foam tape damage the finish on the aluminum if I ever were to take it off? and, How did YOU solve that problem? Thanks again for the help, DioniMike here: 1. No and no. 2. I didn't solve that problem. I had the Scopetronix LightSight mounted in the same position you indicate and had the same problems. Like you I didn't want to run the risk of damaging the tube color! If I had been more careful I would have positioned it slightly differently. An alternative to tape is to use plastic wire bundle straps.
So about the lack of hardstops on the 90 RA, I guess you just keep from turning the scope in R.A. over 180 deg in one direction from home position, right? and: I just used the ETX-90 RA last night for the first time, and was able to get an excellent polar alignment with the help of Dr. Clay's 'Kochab Clock' method and a little luck. I could tell it was good because there was no drift in declination when tracking objects. However, in right ascension, it tracks TOO FAST! With a 26mm eyepiece, objects remained pretty well centered for almost 8 minutes before the RA drift took them off center to the right in the field of view. At 20 minutes of tracking it was right on the edge of the FOV, and at 25 minutes, gone! Are my expectations too high? I mean is that 'just the way it is' with the ETX-90 RA? Can any adjustments be made to slightly lower the 'sidereal' tracking rate? I checked it on objects at 45 deg dec, and at the celestial equator with similar results. Again, thanks for any comments! DioniMike here: There is no "home" position on the RA model; that is used to describe a specific position when using an Autostar. So, no hardstops do not present a problem. As to tracking speed, I don't recall there being an adjustment on the circuit board of the ETX-90RA. However, there are mods you can make (see the Telescope Tech Tips page).
Subject: etx question Sent: Wednesday, August 14, 2002 16:36:19 From: email@example.com (Tom Lakovic) i have an etx question and who better to ask (i thought) than a mega fan of the etx such as yourself...sooo...... if i get an etx-90 without the autostar controller, just the standard hand controller i guess, then can I use my palm's "planetarium" (excellent) software to control the etx instead of the meade autostar controller? i mean a computer is a computer right and the ra/dec motors should respond to anything telling it to move and requesting feedback on where it is, whether it's a standard hand controller, autostar, pc or palm? yes? hope so. i'd like to do photography with it....how good do you think an etx-90 is at photography? thanks tom.Mike here: The "brains" of the ETX GOTO system are in the Autostar. So, to control the ETX you need an Autostar AND the proper serial cable to connect from your computer. As to astrophotography, there are many excellent examples and tips on my ETX Site.
Subject: ETX-90 RA OK? Sent: Thursday, August 8, 2002 11:25:48 From: firstname.lastname@example.org (Dioni Miranda) Thanks again for your time. I own an ETX-125 w/ UHTC and I'm tempted to buy the ETX-90 RA tomorrow ('for the road') from Astronomics (which has 'new' ones on sale for $250) 2 quick questions: 1. I've read a lot on your website about problems the ETXs used to have but where later corrected by Meade. Is it likely that a 'new' (meaning 'just out of the box') RA might have the same 'problems'. In other words, did those 'corrections' apply to the RAs, or just the ECs? 2. I was told that the RA tracks objects, but has to be moved manually by unlocking and locking the two axes everytime you want to see a new object. In your experience (or from what you've heard): Does the constant tightening and loosening of the two axes wear out or have any negative effect on the scope's axes, RA clamps or DEC knobs? Thanks again, DioniMike here: The mechanicals on the ETX-90RA are sufficiently different from the EC model that I doubt any improvements are transferable. Many telescopes require locking and unlocking the axes. With proper care to not overtighten them, they should last many years.
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