The CEM120 family includes two 22 lb (10 kg) counterweights, which is enough for many telescope and imaging configurations. As the payload gets heavier, however, you may reach a point where both counterweights have to sit near the end of the shaft to balance the telescope.
That's where an additional counterweight makes sense. The iOptron #7326 is the standard 22 lb (10 kg) counterweight made for the CEM120, CEM120EC, and CEM120EC2. Adding another weight lets you achieve the required counterbalancing force with the weights positioned closer to the RA axis instead of relying on two weights pushed toward the end of the 540mm shaft.
It is also the correct standard replacement if one of your original CEM120 counterweights has been lost or damaged.
Key Features
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Made for the CEM120 family. Compatible with the CEM120, CEM120EC, and CEM120EC2.
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22 lb (10 kg). Matches the nominal weight of the two counterweights supplied with the CEM120 family.
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Fits the CEM120 counterweight shaft. Designed for the mount's 38.1mm (1.5") diameter stainless-steel counterweight shaft.
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Useful with heavier payloads. iOptron's CEM120 manual specifically notes that additional counterweights may be required for heavier telescope configurations.
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Lets the weights sit closer to the RA axis. Adding counterweight mass allows the same balancing torque to be achieved without moving the existing weights as far down the shaft.
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Replacement or additional weight. Use it to expand the original two-weight set or replace a standard CEM120 counterweight.
When You Need Another Counterweight
You do not need to add counterweights simply because the CEM120 is carrying a large telescope. The correct amount is whatever allows the complete system to balance properly in right ascension.
If the two included 22 lb weights balance your finished telescope and imaging train with plenty of adjustment remaining on the shaft, there is no reason to add another one.
An additional #7326 becomes useful when the existing weights have to be moved close to the end of the shaft, or when adding equipment such as a larger camera, rotator, filter wheel, focuser, heavier optical accessories, or a second telescope leaves the RA axis telescope-heavy even with the original counterweights positioned near their limit.
Adding a third 22 lb weight gives you 66 lb (30 kg) of total counterweight and allows the weights to be positioned farther inboard while still balancing the same telescope load.
Balance the Complete Imaging System
Always balance the telescope as it will actually be used. Cameras, filter wheels, focusers, rotators, reducers, guide equipment, finder scopes, dew equipment, dovetail plates, and cables all contribute to the final balance.
iOptron recommends balancing the CEM120 first in declination by moving the telescope in the saddle, then balancing right ascension by moving the counterweights along the shaft. Both axes should be checked before normal operation.
The goal is proper balance, not simply getting the counterweights as close to the mount as possible. Position the weights wherever they need to be so the complete system remains balanced with the gear switches disengaged.
Loading a CEM120 Safely
The CEM120 is a large mount, and a full telescope system plus several counterweights can represent a substantial amount of moving mass.
iOptron instructs users to keep the mount in its zero position while installing the counterweights and telescope, with the counterweight shaft pointing toward the ground. Install each counterweight securely on the shaft, tighten its locking screw, and reinstall the shaft's safety cap before proceeding.
Hold the telescope or mount whenever an axis is released for balancing. Once the gear switch is disengaged, a heavily loaded CEM120 can move freely if the system is significantly out of balance.
What's Included
- 1x iOptron 22 lb (10 kg) counterweight for the CEM120 family
Product code: #7326
Frequently Asked Questions
Doesn't the CEM120 already include counterweights?
Yes. The CEM120, CEM120EC, and CEM120EC2 normally include two 22 lb (10 kg) counterweights. The #7326 is an additional or replacement standard counterweight.
How do I know whether I need a third counterweight?
Balance the complete telescope and imaging system first. If the two included counterweights can balance the RA axis with usable adjustment remaining on the shaft, you do not need another one. If the weights are near the end of the shaft and the telescope side is still heavy, add another counterweight.
Does it fit the CEM120EC and CEM120EC2?
Yes. All three CEM120 models use the same 38.1mm counterweight shaft and are supplied with 22 lb (10 kg) counterweights.
How much counterweight will I have with three of them?
Three standard CEM120 counterweights provide a total of 66 lb (30 kg).
Does adding another counterweight increase the mount's 115 lb payload rating?
No. Additional counterweights are used to balance a heavier approved payload. They do not increase iOptron's published 115 lb (52 kg) telescope payload rating.
Should I deliberately balance the CEM120 east-heavy for imaging?
iOptron's current CEM120 instructions call for balancing both RA and DEC rather than specifying an east-heavy bias. We recommend following the mount's current balancing procedure and adjusting the counterweights until the RA axis is properly balanced.
Can I use this below 10° latitude?
iOptron specifies a special low-latitude counterweight, #7326LL, for CEM120 installations below approximately 10° latitude. If you are installing the mount that close to the equator, use the low-latitude version specified by iOptron rather than assuming the standard #7326 is the correct configuration.
Will this fit another manufacturer's mount with a 1.5" shaft?
The #7326 is made specifically for the CEM120 family. Even if another mount has a similar shaft diameter, check the manufacturer's counterweight requirements, shaft dimensions, and locking arrangement before attempting to use it on a different mount.
Final Thoughts
The #7326 is a simple accessory with a simple job. If the two counterweights included with your CEM120 balance the finished telescope comfortably, you do not need another one.
If a heavier imaging system has pushed those weights toward the end of the shaft, adding another 22 lb counterweight gives you more balancing range and lets the weights sit closer to the RA axis. It is also the standard replacement weight for the CEM120, CEM120EC, and CEM120EC2.
