Last updated: 28 September 2006
This page is for user comments and information of a general nature or items applicable to all LXD55 and LXD75 models. 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: motor fault related to extra weight of sbig camera? Sent: Wednesday, September 27, 2006 18:21:04 From: jim cadien (email@example.com) I have had my LXD55 for several years now, carrying a black tube C8, without more than the small, usual problems. I recently purchased(used) a Williams Optic Crayford focuser and an SBIG ST7 ccd camera. When I put them on the back, I need a little additional weight on the front of the OTA. The sum of weights of the three items is about 7 pounds. I now need to use two 10 pound counterweights, about halfway on the counterweight shaft. When I start the autostar, things seem fine. The mount slews at high speed. However, after a few minutes of tracking I get a motor unit failure. The system seems well balanced, and the behavior is the same in various positions, with the OTA on both sides of the mount. Do you feel that the additional weight is enough to cause the motor problem? An additional test, with the camera, but not the focuser and the addional weight on the OTA. Needed only one counterweight. This seems to operate ok. Thanks, Jim CadienMike here: The weights, both counterweights and accessories, add mass that needs to be moved. So even though the system may be in balance, getting things moving and stopping could be a problem.
Subject: LX90 groups Sent: Monday, September 25, 2006 07:08:31 From: Moss Colin (Colin.Moss@uk.fujitsu.com) I've read your excellent site on the LXD55 and wondered if you knew of a similar site specific to the LX90 Many thanks Colin MossMike here: There is "Jan's Meade LX90 Pages": m1.aol.com/kewtasheck/lx90.html
Subject: similuarty between LXD75 & LXD55 Sent: Friday, September 22, 2006 18:41:37 From: Harold Ogden (firstname.lastname@example.org) I have an LXD75 with autostar that works fine, I just acquired a LXD55 without a autostar and decided to try it out so I hooked up my autostar from my LXD75 and tried to use it and the LXD55 was squirley the Dec axis kept on creeping after I aligned it? I did not change the setup to indicate that I was using a different head. Are they not the same? HaroldMike here: You need to CALIBRATE MOTOR and TRAIN DRIVES when switching the Autostar from one mount to the other one.
Thanks I only have one Autostar so I won' t use it I bought another one online should be next week, the guy I bought it from was using this one on an ETX70 I wonder if I should clone it from my other one first and then do what you said aroldMike here: Are you getting a #494 AutoStar (which is standard on the ETX-70 and doesn't have number keys) or a #497 AutoStar? The LXD55/75 requires the #497.
I should have told you it's a 497 Harold
Subject: TRIPODS FOR LXD55 SC-8 Sent: Thursday, September 21, 2006 22:14:29 From: LOREN MEECH (email@example.com) Can you recommend any heavy-duty tripods for this telescope (price not a consideration)? I have the equatorial...Mike here: The LXD75 makes a fine upgrade from the LXD75. How much of a heavy duty mount do you need?
Subject: Polar Alignment Sent: Monday, September 18, 2006 09:52:10 From: Dave Wallace (firstname.lastname@example.org) Ken, remember that the polar alignment scope is going to reverse the image left-right. If its field of view were large enough to include Kocheb, then you'd see that star on the opposite side of the polar cross from Polaris when Polaris was in the circle. But you're viewing Kocheb directly when you align the counterweight rod and Polaris through the finder when you try to set azimuth. No wonder it's confusing! Aloha kakau
From: Ken Archer (email@example.com) Actually you are correct! I have an extra Polar finder and just looked through it without the mount attached and the image is inverted. That makes sense to me now. I could not figure what was happening to the pointing. When I carried the LXD-75 head in I felt a clunking turns out the Dec gears were really loose. Duh! Some of us guys are spoiled with the fixed observatories and don't get enough star party setup time. Thanks for the great article it makes sense now and thanks for straightening me out. J Mahalo, Ken
Subject: Re: Pictor Autoguiding: DEC trouble Sent: Sunday, September 17, 2006 03:53:05 From: Gernot Stenz (firstname.lastname@example.org) I would like you to know that I could solve the Problem in the meanwhile. Cleaning, regreasing and readjusting the worm drive brought a slight improvement for the DEC movement. But mostly the success was due to a different preparation of the Pictor calibration routine. Now I move the mount up before starting the calibration so the Pictor can directly move the DEC axis without having to slew across the backlash. Now the pictor successfully guides the LXD, indicated by two pictures stacked from 2 and 4 minute subs: http://www4.in.tum.de/~stenzg/pictures/astro/m16-600mm-120s-2g.jpg http://www4.in.tum.de/~stenzg/pictures/astro/ngc6888-600mm-240s-1d.jpg Thanks everybody, Gernot -- __o Gernot Stenz e-mail:email@example.com /\ -\<, WWW: http://www4.in.tum.de/~stenzg /\/--\ _(_)/(_)_Strasbourg - Paris: 3639 km______________________________/ \
Subject: Polar Alignment question Sent: Sunday, September 10, 2006 18:51:13 From: Ironwood Observatory (firstname.lastname@example.org) I've alway's enjoyed reading your site in fact today I found the information on fixing loose gears on my new LXD-75. I want to ask this ask a question. The article polar alignment http://www.weasner.com/lxd/techtips/polar_alignment.html does not agree with the article about the article showing the Polar alignment scope. http://www.backyardastro.com/addendum/pages/polar_alignment1.htm My email is to only clarify the difference that the cross hair in the polar scope is NCP? The Kocab aritcle it will assumes that Kocab is on the other side of the Polar circle between the end of the counter weight bar and Polaris. Take a look and maybe some clarification. Please I don't want to dis anyone, only clarify. Aloha, KenMike here: The crosshair is the NCP but it is not Polaris, which is about a degree away from the NCP. I think that is what both the article on my LXD site and the one on the other site show.
Yes exactly, but if you have Polaris in the circle and Kochab at the end of the counter weights then the NCP X hair is on the other side of Polaris. Not on a line between Kochab and Polaris. That is the point I am making. Aloha, Ken
Subject: LXD 75 diagram Sent: Thursday, September 7, 2006 08:12:19 From: Rickie Rainwater (email@example.com) I need a diagram of the meade LXD 75 mount. I used your site's tech tips to fix a gear problem, but for dismantling the rest of the mount for inspecting and cleaning the worm gears ect, I could use a diagram. I guess I could wing it, but I prefer not to guess. Thanks, Rickie RainwaterMike here: Haven't come across one.
Subject: Hypertune Sent: Monday, September 4, 2006 15:05:56 From: Steve (firstname.lastname@example.org) I finally did the hypertune, and let me say the results are well worth the time and effort. The mount is now very smooth and quite, and tracks without jerking slipping or backlash. However, I encountered some problems getting there! Most of the problems were with the RA motor. The screws holding it to its plastic case were so tight the Allen wrench stripped the heads. I finally had to cut slots in them with my motor tool and got them out with a regular screwdriver. I replaced them with some short 4-40's. The worst problem was with the RA encoder. After replacing the encoder wheel with the supplied new encoders which I spray painted flat black, I noticed that the encoder wheel hub was so crooked on the shaft that the encoder was rubbing on its pickup for almost half a revolution. It takes a .035 Allen head wrench which is not supplied with the hypertune kit, so I filed down a .050. Allen wrench to get it off the shaft. It turned out that the hub was too large for the shaft and no amount of adjusting would make it run true. I finally shimmed it with a little piece of paper cut from the hypertune instructions, and got it to run dead on. I reassembled everything. When I turned on the mount, the RA motor ran away at high speed, and I got a motor fault error message. I took it back apart and could find nothing wrong. I was afraid I had screwed up the electronics. On a hunch, I looked at the RA pickup under a magnifying glass. Black paint had rubbed off the encoder wheel onto the pick up. After cleaning off the paint, and reassembling everything I still had the same problem! This time I let the motor fault error message run all the way through. At the end of the message I hit the enter key on the handbox as the message instructed. Both motors hiccupped once and then every thing ran perfectly! Apparently, the RA pickup had not been getting a signal due to the paint so the electronics thought the RA axis was jammed. When I hit enter, it thought the jam had been cleared, but still needed to reset itself! Tonight I am going to take it out to the local dark sky site, realign it and retrain train the drives and see how it does. I will let you know..
Subject: Pictor Autoguiding: DEC trouble Sent: Monday, September 4, 2006 05:16:30 From: Gernot Stenz (email@example.com) I have some problems getting the autoguiding on my LXD-75 to work properly. At the moment I have run out of ideas and wonder if anybody here has some knowledge that might help me. I have posted a similar message to the LXD55 Yahoo group. A few months ago I obtained a #909 APM, yet due to bad weather I hardly got to test it. Last month I had a go at a test run and the results were mixed. My setup consisted of an ED80 refractor for an imaging OTA and a 90/1250 Maksutov as guide scope. Guiding was to be done using my Pictor 201XT guider. This weekend I was able to conduct a few more test runs on this matter. Friday night I took a number of 120 seconds subs of Hickson 10, last night I simply centered on Scheat (w/o really perfect polar alignment) and gathered a series of 60s subs. These (for those who are interested) can be found here: http://www4.in.tum.de/~stenzg/hcg10-lxd.zip http://www4.in.tum.de/~stenzg/scheat.zip You can see from these frames that guiding in RA is not a problem (in both cases 2"/pixel). Dec guiding, however, is a really annoying problem. First of all, for some reason the guider calibration was a bit troublesome. I had a live webcam view so I could see the calibration routine go smoothly in RA, yet I always got errors in Dec. Apparently the backlash compensation can be a bit of a problem when the LXD takes too long to reverse the Dec direction. I had to fiddle with the Dec-Percent (between 70 and 80%, quite unusual) and Calibration parameters quite a bit until I got the Pictor to calibrate. The guiding went smoothly at first, RA guiding was flawless and so was Dec guiding... initially. But after a while, when the first Dec corrections became necessary, the trouble began. Two minute exposures showed significant deviations in Dec with RA still perfect. So here I am with a situation completely orthogonal to my previous guiding experience: RA guiding easy, Dec guiding troublesome. I really am puzzled. The Dec worm had just been readjusted (although in much warmer temperatures than we have now), the balancing of the setup was not off by too much, I cannot really explain what caused the not-smooth-at-all Dec movements during calibration. The seeing deteriorated quite a bit later in the night, but if the guider was to chase the seeing it should show up in both RA and Dec. I see the following parameters that can be tweaked: 1) Dec worm play 2) Pictor calibration times 3) Dec gear position before calibration 4) Autostar Dec percent for calibration 5) Autostar Dec percent for guiding I played around with these values quite a bit, but for the time being I can only switch between the guiding lagging behind or the guiding overshooting. For the Friday night run the worm was adjusted rather tightly, for last night I loosened it a bit. Still in both cases Dec corrections seemed a bit jumpy when they fist kicked in and smoothed out only a bit later into the movement (very much unlike the Vixen mount). Does anybody have an idea how to get the Dec drive to behave? CS Gernot -- __o Gernot Stenz e-mail:firstname.lastname@example.org /\ -\<, WWW: http://www4.in.tum.de/~stenzg /\/--\ _(_)/(_)_Strasbourg - Paris: 3639 km______________________________/ \
Subject: LXD 76 RA motor Sent: Friday, September 1, 2006 12:14:29 From: Rickie Rainwater (email@example.com) How do you disassemble the RA motor to check for loose or mis aligned gears? Rickie RainwaterMike here: Remove the inspection port cover on the housing. There is also one on the DEC motor housing.
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