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I just wanted to say hi and thank Ian for starting this group. I just purchasd a GM8 any will no doubt have many questions. In reading the previous posts, I see we are well represented by many knowledgeable people. Brian

>From: "James A. Thibert" <thibertj@...> >Reply-To: sct-user@... >To: sct-user@... >CC: losmandy-user@... >Subject: [sct-user] Backlash is my friend >Date: Sun, 20 Aug 2000 08:14:34 GMT > >Hi Folks. >just got in from an intensive night of running guiding tests getting ready >for next weeks shooting with no moon. >As many of you are aware,my saga of the g-11 has been >ongoing however,ongoing has met relentless! > >I have now improved my g-11 substantially.It's gone from an horrendous 25 >to >40 arcsecs to better than 10. >I got a roll of test shots back the other day showing various length star >shots from 30 minutes to 120 minutes and all show nice round stars even >under 8 power magnification. > >Everything done was recorded so I could give feedback to SBIG's Alan Holmes >who was helping on the st-4 side. > >All in all there were a couple interesting nites when I took the g-11 >completley apart in the dark and swapped gears between dec and ra and >also,tore down the st-4 in the dark to clear condensate and rejuvinate the >dessicant. > >The st-4 ccdtrack program has a number of graphs including an x and y axis >histogram that has gone from looking like the shadow of an elephant to >looking like the empire state building. >Some things that made a difference...3'rd bearing on each axis,200 mag >polar >alignment that stays for 15 minutes east and west,relieve the torque on the >ra gears.Accept some backlash in favour of smoother drive.(plus lapping) >Some things that didn't work or made it worse...tight worm gear,isolating >clutch bearings,isolating the motors, >swapping gears. >Swearing,yelling and karate chops were fun but fall into the latter >category >now that we have sct-users as support. >Thanks to all who helped me out. >Good seeing.....Jimmy >________________________________________________________________________ >Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com > > > > >Visit the sct-user home page at: > > > >http://members.aol.com/RMOLLISE/index4.html > ________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com

I have just been looking at Jupiter and Saturn for the first time through my TV101/G11 combination. At medium power (x100) a vibration of the image was obvious. The vibration frequency seemed to be close to that of the ticking from the RA motor and decreased markedly with the drive off, though did not disappear completely (obviously seeing was effecting the image as well). Before I tear the RA drive apart, does anyone have any views as to what in particular I should be concerned with. Adam Stephens adamstephens@...

As another person has advised on another list, the Losmandy web page on the GOTO has been updated, see here http://www.losmandy.com/newprod.html Greg Crawford

What is the Best grease to use on the G-11 Worm Gear? Fred

I am wondering..... The Sky allows alignment on two or more stars with virtually any set of encoders and mount. You then have "the sky" as a database for targeting rather than the limited library provided by such computer interfaces as the NGC Sky Vector. You would then just point and click your way to discovery and observations. Adding a CCD would add accuracy in targeting the harder to find DSO's. So, if this is the case it would seem a much better idea to bypass the NGC Sky Vector all together (sell it on Astromart or give it ot Michael) and go directly from the encoders to the The Sky software. All one would need is to interface the encoders with computer and The Sky. A simple serial cable of some kind could do this. Couldn't it? Has anyone attempted this?? Would there be a point to this change, or is this a case of fixing something that isn't broken? Thanks and of course, take care. Gregory david Stempel FIREFRAME

Here's what may be a silly question. I recently received my G11 and bought the JMI version of the polar alignment scope for it since it was available now. Is anyone else using the JMI version? If so, what did you find as the most convenient place to put the Velcro tab to hang the illuminator control? Apparently the battery holder/controller can't be disconnected from the polar scope without voiding the warranty, if I read the paper that came with it correctly. Thanks! Doug Culbertson Midway, FL

Out of curiosity, has anyone here ever looked into the possibility of swapping out the S1 encoders on the DSC's with S2 encoders? Difference would be 4096 vs. 8192 in resolution which would translate out to about 6 arc minutes vs. 3 arc minutes. Just wondering, after noticing that the Gemini GoTo system will read out positions from the existing DSC's after a manual slew. I know the housing would need to be modified, but anything else? -- Jim Girard http://www.teleport.com/~argo

Rechecked dec shaft OD, agree that it is undersized by .002-.003in. My vernier calipers aren't that great.So it looks like I have the same problem that has been posted; misery loves company. Bill

Eventually, I received my polar alignment scope for the G-11 from Pocono Mts. Alas, there were no instructions so I tried to figure it out. I thought I did but some evidence indicates that I didn't. Can someone send me to a post that decribes the procedure. Thanks in advance. S. Havriliak

Just thought I would mention that I rarely use the LED with my G11 polar scope. I do my alignments at twilight when the three reference stars and the reticle are plainly visible against the background sky. I think that is why the LED assembly is detachable and a screw-in plug is provided. One problem I found when I adjusted the EP outward to focus the reticle to my eye, there was considerable slop in the threads that allowed the EP to wobble about the main tube assembly.There is no locking ring provided which would solve this problem. This changes the alignment of the reticle superimposed on the starfield looking through the polarscope. Inserting a piece of shim around the EP and tube body took out the slop and allows all the optics to be accurately centered in the bore. Also make sure the locking ring used to attach the polar scope to the mount is tightened down sufficently to prevent any slop in the fit. Check setup by wiggling all parts while looking through EP to make sure there is no shifting of the starfield with respect to reference stars. Your mount alignment is only as good as the alignment of the components of the borescope to each other and the mount. Bill

Does anyone know of a source for undersized needle bearings to fix a weakness in my Losmandy G11 mount? Specifically, 1.247" ID / 1.500 nominal OD. For the benefit of those who may encounter the same problem, I have described it below: With a nominal vertical load, the RA and/or DEC shafts on my G11 mount tend to 'hang' about .002"-.003" below the axis centerline when the clutches are relaxed. When the clutches are tighten, the shaft end plate initially 'locks' to the nylon clutch surface slightly below center. When the axis is rotated far enough that the weight overcomes the grip of the nylon surface, the axis 'shifts' into a 'more' aligned position. This is normal behavior on four different mounts that I have examined. Besides introducing tracking errors, this misalignment distorts the worm/wheel spacing by a small amount, and causes the backlash to vary as the axis is rotated through 360 degrees. Changing the load on the mount, or loosening and retightening the clutches can completely upset prior backlash adjustments. If you are not adjusting your worm/wheel spacing for absolute minimum backlash, you may never encounter this aspect of the problem. The needle bearings on both the RA and DEC are set back about 2" from the 'business end' on each axis. As an experiment, I pressed an additional 1.250" ID needle bearing into the opening so that the shaft was supported nearly to the end of the opening. Additionally, the shafts I have seen measured 1.2470" dia instead of an optimal 1.250". I wrapped some .0015" stainless steel shim stock around the undersized shafts as a temporary fix to remove the bearing slop. Well, it was like night and day. That simple change eliminated the 'shifting' on each axis, improved tracking and GOTO pointing accuracy dramatically, there was no more slop in either axis, and best of all, the backlash can be adjusted to virtually zero through a full 360 degrees of rotation. Anyone else have a similar experience? Neal

There is an alternative to the Losmandy and Gemini, at http://ds.dial.pipex.com/awr.tech/ I have one attached to a GP mount, its OK but does not have all the functions in the losmandy or Gemini goto system.

I'm looking at goto systems for my gm8. Does anyone know if the astrometric is better than losmandy gemini? I'm concerned with function, fit and finish, quality and craftsmanship. I appreciate the info in advance. skygazers

I own a gm-8 with a tak fs102. I'm looking into a goto for the mount. Obviously, it's a choice between the astrometric skywalker 2 or the losmandy gemini. I like to know which system is better in terms of performance, quality, finish and cosmetic appearance. Astrometric claims a slew rate of more than 6deg/sec while losmandy states just 6deg/sec. I'd welcome any information as to the better system. Thanks.... skygazers@...

I need help with two problems that I encountered with the Losmandy Delran covers for their DSC. First, let me describe the anomolus behavior. When manually centering on a star using a Telrad finder, the centered star drifted about 2 deg. after I removed my grip from the SCT. Also, when shifting a star from one end of the eye piece field to the other using the dec drive, the star stoped moving. The scope is accurately balanced. 1. I followed the installation of the DSC and covers with great care using the eploded view in Losmandy instruction sheet. After the incidence described above, I took the Losmandy covers off and found that the rubber O-rings were torn in half. 2. After re-assembling the DSC with covers, I noticed that the covers moved with rotation (about a degree) about the Dec. axis. The net result is that the covers moved against the gears and significantly increased drag. This drag is probably sufficient to stall the motor drive. The net result is that movement about the Dec axis is similar to serious back-lash. Close inspection showed that there was no back-lash in the gears, it just felt that way. 3. Removal of the cover and rotation about the Dec. axis showed that there is no apparent back lash. Further more there is no apparent increase in drag. Any suggestion is greatly appreciated.

Hey Guys, Maybe I missed it, but is there any kind of lubricant that works better than another when re-lubing the GM-8/G11 mount. Would White Lithium be best? I also heard that green bicycle stuff is good. Please advise. Milton

I am an Italian amateur astronomer. I have a problem with my brand new G11. Since the day one, I noticed a play in the declination axis. It becomes very evident when the saddle plate is rotated at a particular angle with respect to the mount. In this condition, if I grab the saddle plate I clearly feel the play (about 1/3 of degree) that starts decreasing as soon as the saddle plate is manually rotated by about 60 degrees. It disappears once the DEC axis is rotated by 120 degrees and starts increasing again at about 300 degrees. Some Losmandy users suggested that the play is related to the mechanical fixation of the declination axis to the saddle plate assembly. They also said that their mounts have a set screw that locks the saddle assembly to the declination axis, but I could not find that screw in my mount. Maybe Losmandy changed the G11 shaft DEC assembly (can anybody confirm that?). I would really appreciate if someone you could help me to solve this problem. Thanks in advance. Clear skies! Girolamo Gallo Avezzano, Italy

Hello, I am hoping someone may be able to help. I have a GM-8 and there seems to be a problem with RA function. It's axis has shifted some 20 degrees. If I position everything on the entire mount head as if it came out of the box, the RA motors, bearing and housing now sit at an angle to everthing with the motor assembly sitting lower and the right side (looking at the mount from the side of the alt-adjust) pointing higher than it used to. If you look at your mount, imaginge the bolt which holds the worm gear's bearing housing (the housing closest to the RA moto)r now positioned over the curved portion of the alt-adjust bracket at the base of the mount. I took the mount completely apart last night (easy to do if anyone needs instructions) all the way down to main housing. The part which has shifted it's position is the only part that had no apparent way to be disassembled. As if it were pressed in like bearing on auto axels. It will not move, and is tight as a rock......as if that is the position it is meant to be in. Am I just imagining a problem?? The mount seems to work fine, just does not look like it used to. Thanks for any help in advance and take care out there, Gregory david Stempel FIREFRAME

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