The important thing to understand here is that the magnetic disc does NOT rotate. I super-glued it because the central hole in the rubber washer was far bigger than the diameter of the bolt, so I needed to stop it moving around. Rotate the telescope anti-clockwise slowly through a full 360 degrees. Addition of a Lazy Susan Turntable to the Azimuth Bearing. The key thing then, is to ensure that when a Lazy Susan bearing is inserted, which due to its thickness usually results in increasing the size of the gap between the top and bottom base boards, that additional packing in the form of extra washers needs to be inserted underneath the magnetic disc to hold it up against the brass bush. The lower line of the display corresponds to the Azimuth Encoders. The scope pivots vertically from horizon to zenith on these altitude bearings, one of which is shown in Figure 3-30. This second photo shows the parts divided into their relative positions above, between and below the top/bottom baseboards. This is also a symptom that the magnetic disc has become bent, and so at some point in the rotation comes too close to the chips. If this does not help you may need to disassemble, inspect for problems and re-assemble. But also just a positive sidenote: A (heavy wooden) Dobsonian mount is much more solid and often far less prone to vibrations than EQ mounts! A properly balanced scope will help alleviate any of these problems. You will learn a great deal from this link. Copyright (c) 2016 All rights reserved. There is also a short movie clip you can view to see the effect of the new bearing. In the right-hand photo you can see a nylon washer that I placed over the brass bush to fill this gap, because whenever I lifted the base, the bottom section would drop down by this gap distance, making an un-nerving "clunk" sound. Dobsonian telescope mounts move in altitude and azimuth on friction bearings. Generally I much prefer the smoothness of the lazy susan, but it can sometimes be annoying having to move so gingerly around the scope if I have aligned it on something, and want to change the eyepiece for example. The fear is that of the magnetic disc coming into contact with either of the two electronic sensor chips that protrude slightly above the circuit board. The bearings do have a notching effect sometimes, i.e. When you first power up the Intelliscope the sensor readings will be zero, so the startpoint would be different every time you do the encoder test (i.e. prevent wind blowing the scope around, accidental nudges or movement on unlevel ground), is a matter of trial and error. google_ad_client = "pub-0336444338641900"; DOBSONIANS are intended to be simple, cheap mounts. Click the link below to view a short Quicktime movie demonstrating the effect of the bearing on the Dobsonian base after the Lazy Susan has been installed. you move the scope but the bearings want to roll it back or fore slightly before it rests. I think the low cost of the lazy susan might warrant a 2-yearly renewal? //-->, AC_FL_RunContent( 'codebase',',0,0,0','width','108','height','28','title','AstroMusic','src','../mp3s/AstroMusic','quality','high','pluginspage','','bgcolor','#0B0529','movie','../mp3s/AstroMusic' ); //end AC code. google_ad_width = 336; If your telescope includes the Intelliscope Computer Object Locator system, then you should perform the following test procedure to establish correct operation of the Azimuth encoder. google_ad_slot = "7522784574"; After installing my own LS (Lazy Susan) bearing, plus "carpet" brakes I did a centre of gravity test to see how much tilt was required from dead level before the scope became unstable and started to move "downhill". Middle section: You can see the addition of the black rubber washer, plus one of the original metal washers, at middle of the photo. Use of counter-weights to balance each end of the scope will help. My gut feeling is that by some mistake they have either caused the critical gap to widen or close up, rather than actually causing damage, but thinking they have damaged it, request a new encoder board without attempting to revert to the original build to see if it still worked. Radius above 125 means "too close" and below 30 means "too far apart". If you think they could be improved please let me know! If the marks do not line-up, this indicates that there could be some slippage, possibly because the magnetic disc is not being held tightly enough against the bottom base board washer. If the magnetic disc somehow becomes misaligned and tilted so as to come into contact with the chips, but again I think this would require considerable mishandling of the scope, or not enough care when re-assembling the azimuth bearing, for instance letting the magnetic disc slip, If additional washers are inserted in the. Next we will use the Alt Azimuth Readings Test. IMPORTANT: Once you have re-assembled the scope rotate the base very slowly listening carefully for any nasty noises, and feeling for any points of resistance that might be caused by incorrect re-assembly of the Dobsonian base. The upper line corresponds to the Altitude Encoder, which we will ignore. Some fine-tuning of the braking system may be required, either with different sizes of "carpet brakes", or by tightening or loosening of the central bolt if you employed the Clunker washer braking method too. Rotate the telescope until the bottom right figure shows +000.0, then without moving the base make a small pencil lineup mark on the edge of the top and bottom base boards to note the starting or zero point. Mark through the mounting screw holes, then remove the bearing before you start drilling else sawdust could get into the bearing rollers. This page details the addition of a ball-bearing "lazy susan" turntable to the main azimuth bearing of the Orion XT scopes, as previously discussed on my introductory page about the dobsonian azimuth bearing and stiction. Bottom Section: The main bolt and second original large washer remain the same, passing up through the whole assembly. Ooops. I placed various thickness items under one of the base feet, and when I used a book about 3/4" thick it was then that, with the scope tube at horizontal altitude, gravity would cause the scope to overcome the friction of the "carpet" brakes and rotate downward to its lowest point. If the tape holds securely enough then that's fine, otherwise I can use some alternative stronger adhesive once I know the correct amount of carpet required for the brake to be just right. The top line corresponds to the Altitude Encoder which we can ignore (showing value +000.0), and the bottom lines is for the Azimuth Encoder (value +002.8), which we will check. I do sometimes feel that the Teflon pads and stiction approach, if maintained well, offers better control for wide viewing. The photograph below shows the Azimuth Bearing. While this mod refers in particular to my Orion XT10i telescope, the same principle should apply to the other models in the XT range provided care is taken to measure and order an appropriately sized alternative "lazy susan" for the smaller models; the XT6 and XT8. The only way damage can occur is; I know from research that some people have reported the Intelliscope not working properly after making modification to the bearing. IMPORTANT: Following the modification and re-assembly of the base, you should perform an Encoder Test which is one of the "Hidden" Functions detailed in section 12 of the Intelliscope COL Instruction Manual (page 22,23). I keep returning to the KISS notion - Keep It Simple Stupid! Check the ALT AZM TEST goes fully through from 0 to +179.9, then at 180° rotation the figure swaps to negative -179.9, and continuing rotation returns thru negative values to 0, back where it started. Please note that only latin characters, numbers and common special characters can be entered. google_ad_width = 120; If you wanted high precision, you should have paid for a quality EQ mount!!! The lock nut presses the fender washer down on the nylon washer to produce the friction you want. An example of the kind of issues discussed can be found on this topic thread at the Cloudy Nights Forum:-, Cloudy Nights Thread Link: Lazy Susan for Intelliscope. In the left photo you can see what I call the "clunk" gap created by the brass bush protruding above the top baseplate, between the top plate and the washer/nut of the bolt (although photo is sideways on).