iOptron ZEQ25GT Review

After reading a few good reviews for the iOptron ZEQ25GT, I decided it would be an ideal mount to use for astrophotography. It was reported to be lightweight but with a decent payload, accurate, and quick to polar align. My plan was to use the ZEQ25GT with my Orion Eon 80mm refactor for deep space imaging and 9.25″ Celestron SCT for the planets. This review covers my initial impressions of iOptron’s unique Z-designed equatorial mount.

There were a few different options to select from when I was shopping for the ZEQ25. Here are some of the choices I saw online:

  • Mount with 1.5″ tripod (no polar scope)
  • Mount with polar scope and 1.5″ tripod
  • Mount with polar scope, hard case, and 1.5″ tripod
  • Mount with polar scope and 2″ tripod
  • Mount with polar scope, hard case, and 2″ tripod.

I decided to purchase the last one with polar scope, hard case, and 2″ tripod. My plan was to eventually take this setup to a dark sky site for deep space astrophotography. The hard case would be good for transporting the mount and the 2″ tripod would provide more stability over the 1.5″. The polar scope was a must for minimizing setup time.

ZEQ25GT Setup

Putting together the ZEQ25GT was a fairly easy process. Like many setups, the mount attaches to the tripod with a threaded center rod that goes through the accessory tray and into the bottom of the mount. When the center rod is tightened, it spreads the tripod legs to stabilize them while securing the mount to the tripod. I assembled everything in just a few minutes. Setting up the ZEQ25 for the first time was an interesting process though! The Z-shaped design seemed so odd at first since it is different than a German Equatorial Mount. I had to check the user guide a couple of times to make sure I did it correctly! The concept according to iOptron is that the “Z” design mount puts the weight of the payload at the center of gravity allowing for greater natural stability. Here are photos of two iOptron mounts. The first is the ZEQ25 with Z-shaped design and the second is the iEQ30 with standard GEM design.


I found that the ZEQ25 balances the load exceptionally well. The mount is super smooth in both R.A. and DEC once it is balanced. The only time it didn’t balance perfectly is when I used my 6″ Meade SCT with finderscope. The finderscope is offset to one side (shown below) and heavy enough to influence the balance. I fixed this by removing the finderscope and installing a lightweight Orion EZ Finder II Telescope Reflex Sight in the center.

ZEQ25GT Balance

ZEQ25 Saddle- Important!

Here is an important issue to be aware of. The saddle of the ZEQ25 has a ridge down one side that can catch the dovetail of your optical tube making it feel secure.  The optical tube seems tight in the saddle but can actually fall off. This happened to me when I was balancing the mount. Luckily my lightweight optical tube hit the soft grass and survived with no issues. iOptron made the saddle this way to accommodate some dovetail plates that are not flat. The problem can be eliminated by filing a bevel on this ridge following this procedure. I ended up installing a replacement saddle from ADM which eliminated the problem. The ridges on the ZEQ25 saddle are shown below. Click on image to maximize.

iOptron ZEQ25 Saddle

Gear Switches and Tension Adjusters

The ZEQ25 uses gear switches to disengage the worm from the worm gear so the mount will swing freely in R.A. and DEC. It also has tension adjusters which allow for fine tuning the mesh between the worm and the worm gear for optimal performance. This takes a bit of getting used to! In order to manually slew the mount in R.A. or DEC (to balance the mount for example), the tension adjusters need to be loosened which requires several turns. Then the gear switch is opened to disengage the worm from the worm wheel so the mount will swing freely. The process is reversed for locking the axis back. The trick is to apply enough tension to remove any play in gears but minimize force on the worm assembly.  Contrast this with a German Equatorial Mount which involves simple clutch locks to disengage and engage the gears. The image below shows the tension adjusters for the RA and DEC axis. The DEC gear switch is also shown (RA gear switch located on other side). Click image to maximize.

ZEQ25GT Tension Adjuster and Gear Switch

The user guide provides this information regarding the gear switches and tension adjusters:

The Tension Adjusters are used as the last step to lock, and the first step to release the gears. When disengaging the gear system, release the Tension Adjuster first. Then turn the Gear Switch to OPEN position. When engaging the gear system, turn the Gear Switch to LOCK position first. Then tighten the Tension Adjuster. Never fully tighten the Tension Adjusters during operations.   Fully screw in the Tension Adjuster and then back out by about 2 turns.  The optimum spot varies with actual conditions, but is mostly within 1-3 turns from the fully tightened position.  Ideally, it should be at a position just deep enough to rid any free movements (plays), while force on the worm assembly is kept at a minimum.

It doesn’t take long to get used to this process and provides for control of the gear mesh to optimize performance. I’m just spoiled with the traditional clutch locks on a GEM!

ZEQ25GT Polar Scope

Before purchasing the ZEQ25GT, I had heard that the polar scope was one of the best in the business. Now I understand why! The polar scope incorporates an illuminated reticle based on the radius and angle of the star Polaris (or Sigma Octantis in the southern hemisphere) from the true center of the pole. See image below. As long as the mount is level and the time and site information is correct in handset, a good polar alignment can be achieved very quickly.

ZEQ25GT Polar Scope
When I first tried the polar scope though, the view was not very clear. I was a bit disappointed with the slightly blurred view. But I quickly figured out that it had a focuser as shown below. I didn’t see this mentioned in the ZEQ25 user guide. After adjusting the polar scope focus, the view was crystal clear!

ZEQ25 Polar Scope Focus

The ZEQ25 hand controller shows where Polaris should be located on the polar scope’s illuminated reticule.  This information is found by pressing the MENU button, then selecting “Align” and “Pole Star Position” to display the current Polaris position on the reticule. However, I found a better way to do this based on a tip from Paul Chasse who is a well-known expert on iOptron mounts. Paul appears on various forums where he offers advice and tutorials on various types of astronomy equipment, particularly iOptron products. As a side note, Paul offers nice upgrade accessories to iOptron mounts such as a ZEQ25 Altitude Locking Knob, ZEQ25 Dual Spring Kit, ZEQ25 Oversize Knob Kit, ZEQ25 Dual Spring Kit, ZEQ25 Polar Scope Spacer, and ZEQ/iEQ30 Padded levelers. See Paul’s ZEQ25 products here.

Paul was helping me with my polar alignment one night and mentioned that he uses the app iOptron Polar Scope which is made by iOptron for iPhones and iPads. Since my smart phone is on the Android network, I needed a different app. I found Polar Finder made by TechHead. It has a list of telescope mounts which includes iOptron. This app made it easier than the ZEQ25 hand controller to pinpoint where Polaris should be located on the reticule. Using this app, I just adjusted the azimuth and altitude knobs on the ZEQ25 to position Polaris in the same place on the polar scope reticule as shown by the app. The result was quite exciting the first time I used the app! In a 12.5 mm eyepiece (and f/10 scope), Polaris stayed in the middle of the eyepiece field of view for several minutes before there was enough drift to be noticed. Here is a screenshot of the Polar Finder app:

ZEQ25GT Polar Scope App

I think my polar scope may have shifted inside the mount over time since the polar alignment wasn’t working so well after a few uses. I ended up performing the BrightStar Polar Alignment that is available on the handset. This took longer than using the polar scope but it was an easy process. When I polar aligned the ZEQ25 this way, I looked through the polar scope and Polaris was no where to be seen. I contacted iOptron Support and they provided instructions on re-aligning the polar scope. As of this writing, I have not tried it. I do want to mention though that iOptron’s Support is some of the best I’ve dealt with for astronomy gear! I’ve heard others say this as well.

ZEQ25GT Payload

The advertised maximum payload capacity for the ZEQ25GT is 27 pounds. So my intention was to use my 9.25″ SCT on it for planetary imaging. The 9.25″ weighs 20 pounds and with a small planetary camera (such as ZWO ASI120mm), focuser, finderscope, and TeleView 2.5X Powermate, it should be just below the payload maximum. I realize that the maximum payload rating of any mount is meant for visual astronomy, not astrophotography. But I had read that the ZEQ25GT handles heavy loads near the maximum or even exceeding the maximum very well. I wanted to try it!

After I attached the 9.25″ SCT to the ZEQ25GT, I realized that this tube was too large and heavy for this mount! See image below. It felt WAY under-mounted to me. Maybe it’s because I was used to my SCT being mounted on the beefy CGEM that I used before. But it made me super nervous on the ZEQ25GT even when it was balanced. I removed it immediately. I ended up buying a 6″ Meade SCT which seemed perfect for the ZEQ25GT as did my 90mm Orion EON.

ZEQ25 with 9.25" SCT

Zero Position

The user guide refers to the mount’s zero position which is the default position of the R.A. and DEC axis. According to the user guide, the mount is in the zero position when the counterweight shaft is pointing to ground, telescope is at the highest position with its axis parallel to the polar axis and the telescope is pointing to the North Celestial Pole (if you are located in northern hemisphere). I was surprised to find that there were no index markers built in to the mount to make this an easy and accurate process.  Fortunately, there is a great tutorial by Paul Chasse on how to add your own markers:

Go2Nova® 8408 Hand Controller

I found the ZEQ25’s hand controller to be fairly straight forward to use. The interface seems very intuitive for setting up the mount as well as operating it. The only issue I ran into during my initial trials of the mount is that the hand controller did not retain the date and time. When I first turned it on, the display defaulted to 2011-01-01 and the time was way off.

iOptron ZEQ25GT Controller

I had to set it to the correct date and time each time I turned on the mount. All was good as long as I left the mount on. One issue though, the ZEQ25 instructions say to return the mount to the zero position after polar alignment and to set the hand controller back to the zero position as well. The instructions say the easiest way is to turn the scope off then back on. This would reset my hand controller to the wrong date and time again though. Anyway, it turned out that the battery inside the hand controller was low. This was easy enough to replace. The back cover of the hand controller is removed by 4 screws and the battery is replaced. The battery is a common button battery (CR1220). After I replaced the battery, it held the date and time just fine.

ZEQ25GT Hand Controller Cable

As with many telescope mounts, the coiled cable for the hand controller does not extend far enough for convenient use. It’s not bad if you are right at the scope operating it, but if you are sitting at a laptop two or three feet away and trying to use the controller, it’s a bit difficult to deal with. Fortunately, extension cables are available here at AstroPhotography Tonight that will take care of this. ZEQ25GT extension cables here.

iOptron ZEQ25GT Coiled Cable

Overall Impression of ZEQ25GT

The ZEQ25GT really is a nice mount in terms of portability, minimal setup time, accuracy, and smoothness of operation. I got a chance to use it for astrophotography of the planet Saturn with my 6″ Meade SCT. The ZEQ25GT did a nice job of keeping the planet centered while I captured the video. As of this writing, I probably will not keep the ZEQ25GT since I want to go back to a beefier mount that will handle my 9.25″ SCT better. But I do highly recommend the ZEQ25GT for those with a lighter setup such as a refractor for deep space imaging. I didn’t get a chance to test the tracking at great lengths, but I’ve heard it does exceptionally well at this. Below are my Pros and Cons for the ZEQ25GT. I hope this review has been helpful. Please feel free to post a comments in questions below.


  • Very light; easy to transport
  • Decent payload for light mount
  • Very smooth and balances nicely
  • Polar scope makes it easy and quick to perform a polar alignment
  • BrightStar Polar Alignment easy and fairly accurate
  • Goto’s accurate
  • Fairly quite during slewing
  • Control over gear mesh with switches and tension adjusters
  • Very straight-forward operation of hand controller
  • Excellent tech support by iOptron
  • Great tutorials available by Paul Chasse


  • Optical tube can fall off due to ridges on saddle plate
  • Hand controller cord too short
  • Cannot look directly down on bubble level. The mount obstructs the view slightly
  • No index marks on mount for lining up at zero position
  • Gear switches and tension adjusters take time to get used to
  • GPS takes several minutes to sync

This iOptron ZEQ25GT review was:

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  1. Stability – did you see much vibration? Did it damp any vibration quickly? I have a C-6 but would likely use a C-8 for imaging.

    1. AstroPhotography Tonight

      Hello Ed,
      It’s been awhile since I used my ZEQ25, but seems like the vibration settled fairly quickly. Note that I used the 2″ tripod.

      Ray Shore

  2. I like chasses tutorials, and mount is good light size, but could you please give your opinion on other like mounts for comparison.thanks, i have 4 ” tak scope ,wonder whats best

  3. Thank you for publishing your review. There appears to be a lot of discussion on the forums about this mount but very few have made the effort to quantitatively evaluate it.

    There has been a lot written about the gear switches and tension adjusters due to the fact that iOptron have underestimated the need to educate their users about the mechanism, why it is different to others and what advantages it provides. In the first few months there were reports of users burning out their motors because they overtightened the tension adjusters because they were treating them as axis clutches! The design is meant to remove play in the worm drive by providing a small amount of spring loading between the worm drive and the gear so that they stay in contact at all times. The tension is adjustable to cope with varying loads. Other mounts in this class have a fixed worm drive mechanism which are prone to wear and poor adjustment.
    Understanding how it works makes it easier use it – set the tension to be just enough to hold the load with no discernible slop ( it can be tricky because using too much force will cause the worm drive to ride up the gears which may feel like slop ). Once it is set there is no need to release it to disengage the gears – turning the gear release knob 90 degrees will lift the whole worm drive mechanism off the gear and it will swing freely. Turning the gear release knob a further 90 degrees will re-engage the mechanism and you should feel it locking into place. This really is no different to traditional clutches on normal equatorial mounts except that the gear release knob is really tiny compared to a clutch lever and normal equatorial mounts don’t have easily accessible worm drive adjustments.

    The second point is regarding the zero point which has garnered a lot of attention in the forums. Its only value is to provide a reference point if the gears have been disengaged for any reason after the mount has been aligned. You have to power off the mount, attempt to align the marks back to the zero point and power on the mount. There may be errors in aligning the marks because it is visually hard to determine a perfect match and the worm gears may not be meshing perfectly at the zero point. The bottom line is that it may not be aligned as well as it was before the zero point process. I find it simpler to do a 1 star align (assuming the mount is already polar aligned).

  4. Curious if you have had an issues or problems with this mount since the review? I have been reading a few topics on forums that discuss a re-occurring issue that seems to not be fixable, or worse requiring the mount be sent back to iOptron multiple times(seems to take the low cost out of the equation fast if you start adding in shipping cost and labor).

    1. AstroPhotography Tonight

      Scott, I did not have any other issues since the review but I didn’t keep the mount much longer either. I moved to the CGEM DX since it would handle the 9.25″ SCT better. Sorry I’m unable to provide any further input. Ray

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