DS Mount Mods
One of the two scopes I have is a DS-114 with autostar. I am always looking to improve this scope's performance. There have been many tweaks during the past couple of years including the 495 -> 497-firmware upgrade. See http://www.weasner.com/etx/autostar/as_495-497.html . The optics in the scope is pretty good and the motor system I believe to be very good, but the mount is terrible. There seem to be about 3 degrees of slop in the altitude axis. The azimuth is not that bad and will be another project. With the OTA level and the clutches engaged the tube can be lifted about 3-inches before resistance is felt. This rocking of the OTA in the vertical produced noticeable back and forth movement in the Alt. clutch knob. Disassembly reveled lose bushings on the axle. I decided to replace the drive side bushing with Torrington B-810 Full Complement steel roller bearings. These bearings have a rated working load of 2,590 Lbf., a shaft diameter of 0.500 inch; bore diameter of 0.7500, and a length of 0.625 inch. They cost about $4.00 each.
Complete disassembles of the gear and clutch housings are required. Refer the scopes manual for the schematics. Disassembly of the scope's saddle area was tricky. There is Locktite or some form of locking cement on the nuts in the plastic saddle that prevents unscrewing the shafts. Fortunately there was enough flex in the saddle on my scope to slip the saddle off the nuts. If anyone tries this be careful not to break the plastic saddle. An
11/16-tappet wrench and screwdriver might be a safer approach if you have one. Just flex the saddle enough to slip the thin wrench over the nut between the fork and saddle. Once the saddle is removed, a 11/16 wrench and flat screwdriver will remove the shaft
Once the shaft is removed it will have to be machined down on the bearing end to 0.500 inches diameter. The area for the bearing will have to be lengthened by the difference between the old bushing and the new roller bearing to accommodate the longer roller bearing. Mine was about 0.125 inches
.
Press the old bearing out of the fork arm. The fork arm will need to be bored out to accommodate the larger outside diameter of the roller bearing. Be careful in this step to maintain shaft alignment with the opposite side. It is better to undersize the bore and the ream the hole to the proper diameter. The fork is very soft metal and tool wobble will easily make the hole too large. Once bored carefully press the new roller bearing into the fork arm.
Reassembly will be easier than disassembly because the nut can be placed in the plastic saddle and the saddle put in place before the shaft is screwed together. Don't forget the thread locker.
After complete reassembly the amount of end travel with the OTA in the horizontal was slightly less than 3/4 inch. This is a big improvement over the previous 3 inches of play in the vertical movement of the OTA. Most of this I believe to be in the clearance between the shaft and the small gear that the worm turns.
Make sure you get the worm gear housing properly mounted. I have worked on 2 DS-114 scopes and both came from the factory with the gear housing improperly mounted. That's nearly 100% faulty. Make sure the three screws are all the way home. If the stick up just a little they can drag on the clutches.
Testing:
After motor training the scope, I aligned using a 33mm eyepiece. The GOTO's hit near the edge of FOV, not as good as I had hoped. The problem now seems to be in the AZ axis. Once I figure out the how to deal with the vertical load (thrust) I will convert the AZ axis to steel roller or ball bearing. A bonus of all this is that there are no motor induced vibrations in the OTA. They are now almost non-existent. Looking at Jupiter through a 6.4mm gave sharp views of the belts and stars remained pinpoints with the high power eyepiece. I previously had to unplug the power and stop the motors to get such a steady, but brief view. After adjusting the gear train and retraining the motors, the GOTO's improved slightly, missing M11 and some nearby NGC objects just on the edge of FOV. However a GOTO M13 hit almost dead center. That is after slewing about 3/4 the way around.
Conclusion:
The modification did not produce the precise GOTO of my LX90 as I had hoped, but getting rid of the motor induced vibration was well worth the effort.
Disclaimer:
AS always use this information at your own risk. These modifications will most likely void any remaining warranty by Meade. Results can vary by skill level of the person doing the modifications.