Whether observing or imaging, poor or aberrant tracking or autoguiding, spontaneous slewing, or the need to constantly reboot or realign our telescopes make our limited time in the field much more difficult.
After experiencing several such imaging sessions, each one slightly worse than its predecessor, I began to notice a serious deterioration in my telescope mount’s performance. I could no longer autoguide my telescope for more than 60 seconds, without seeing noticeable star trailing in the images. Furthermore, my telescope began to periodically slew in random directions, requiring a complete reboot and realignment of the instrument each time. Since my telescope mount was no longer covered under warranty, any instrument repair could end up costing me as much as it would to purchase a brand new mount. Furthermore, telescope mount repair meant sending the mount away for repairs for several months, so I began to research how to repair my telescope mount, and I found the answer in Hypertuning.
Hypertuning is the process of complete disassembly, repair, and reassembly of a telescope mount. It is not a task recommended for those with limited mechanical aptitude, or for people who are afraid of taking a risk with expensive equipment. After evaluating the risks, I decided to purchase a Do It Yourself Hypertuning kit from a company in Arizona. What I did not realize was the extreme level of work Hypertuning would entail.
After unpacking the Hypertuning kit, I watched the 3-hour long 2 DVD set that came with the kit. The DVD’s contained complete instructions, an example of mount disassembly, repair, and reassembly, a list of tools necessary, and a list of worksheets for computations. The, Hypertuning kit also contained grease, thread lock, 15 Teflon spacer rings of varying thicknesses, 4 ceramic bearings, a brush, metal polish, an adjustable screwdriver, a set of metric Allen wrenches, and a handcrafted tool for removing retaining rings. Additional tools and items needed were a Vernier Caliper, a pair of snap ring pliers, 4 disposable plastic food storage containers, and, in some cases, a vise or a small propane blowtorch.
Total Time Elapsed for the Project: 3 hours
As a former machinist, I consider myself to have fairly good mechanical aptitude, yet the disassembly took quite a while to complete, as I was following each of the steps in the DVD. I removed the mount saddle, Dec clutch, and the Dec drive assembly.
Each assembly was broken down further into its constituent parts, roller bearings, taper bearing, housing, spacers, retaining rings, ring gears, worm gears, spur gears, motor gears, and motor. After removing the RA drive assembly, I noticed a pitted area inside of the mount housing. It turned out to be a defect in the casting of the mount. The surface was pitted and rough, and may have been the cause of large deviations in my autoguiding, as the ring gear may have been sticking on the defect, and then breaking loose. After removal, each gear was cleaned. The gear body was sanded down with sandpaper, cleaned again, and then refitted inside the mount, without grease, to check for potential binding. Then, the gears were polished, and set aside.
A Vernier caliper was used to take eight measurements, to determine proper spacer thicknesses between the bearings and the mount housing. The mount housing was cleaned and sanded down in the pitted area. The mount housing and bearings were cleaned to remove all grease, and then re-greased with the grease provided in the Hypertune kit.
Total Time Elapsed for the Project: 13 Hours
The new bearings were inserted on the ends of the RA and Dec worm gear assemblies, outside of the respective spur gears. The spacers were re-inserted in the appropriate places, the gears were re-greased and the RA and Dec assemblies were re-stacked and re-inserted into the mount housing. The new motors were each tested, by plugging them into the control circuit board, powering up the board, and turning the motors in both directions. The gears were re-attached to each motor, and the motors were re-inserted into the mount. The spacing between the motor gears and the spur gears was manually adjusted to ensure minimal backlash on both axes, and the mount was closed up. Additional fine tuning of the backlash settings was made using set screws on the exterior of the mount. The saddle was replaced on top of the mount, and bolted in place. The mount optical tube assembly, guide scope, and all counterweights were placed back onto the tripod, completing the process.
Total Time Elapsed for the Project: 20 Hours
Total Cost Savings vs. off-site repair and Hypertune:
It costs $200 more for the Hypertune kit if it is purchased for off-site use, and postage for the mount can be expensive (approx. $400 for both directions, including insurance, for mine), so I saved roughly $600, and, off-site repairs may take several months’ time, depending upon the telescope manufacturer.
Is Hypertuning Worth Attempting by Yourself?
The short answer, in my opinion, is yes and no. The cost and time savings were significant, and I learned a lot about how my telescope mount works, but this is clearly a job for two people. There were several, “oh, by the way” statements at later points in the DVD program that prompted me to re-evaluate what I was doing, and allowed me to avoid potential pitfalls, so I would recommend watching both DVD’s in their entirety, prior to attempting any work on the mount. The extreme care with which you have to handle each of the gears makes Hypertuning extra difficult. You cannot drop any of the gears, while polishing, sanding, cleaning, or greasing, as the gears may be damaged, permanently ruining the mount. And the risk of introducing foreign contaminants into the gear teeth is high, as the gears are exposed, when removed from the mount housing. Lastly, Hypertuning a telescope mount takes focus and determination, and I would recommend minimizing any interruptions and taking your time if you decide to undertake this difficult endeavor. After all, the last thing you want is to have “spare parts” left over. Clear skies!
I then removed the RA clutch and RA drive assembly, and the motors.
“Hypertuning a Telescope for Improving Performance”
By Eric Bowen