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iOptron GPS Cube GOTO mount

Posted by Malcolm Bird   02/22/2010 12:00AM

My name is Malcolm Bird and I have been in and around the Astronomical community for the last 15 years. I formed and ran Talscopes in N.America for a couple of years, and have owned and used many of the commercially available telescopes. (providing they didn’t cost more than my car…). I currently own an 8”LX200, C5 and 80ED. I am not affiliated with any Astronomical company. The opinions expressed in this article are mine alone.

Like many people, I was intrigued by the iOptron ‘Cube’ when it debuted a while back. And like many people I was also frustrated by the lack of any real information or reviews on this product.

I had a C5 OTA that needed a mount, and an old CG1 mount from my Astrojunk just wasn’t up to the task. What I really wanted was a light, GOTO grab-and-go set up. Could the iOptron Cube be it?

So I decided to take the plunge and bought a nearly new Ioptron GPS ‘Cube’ off Astromart. It did not arrive in factory packaging, so I cannot comment on this aspect of the product.

First Impressions

When you are first presented with the cube, it looks pretty much like its pictures in the ads. However, it has more heft to it than its shape and pastel color scheme suggests. Fit and finish are on par with any piece of Chinese consumer electronic gear these days – which is to say, very good! The basic ‘kit’ includes the ‘Cube’, hand controller, tripod and spreader/tray (which I unfortunately managed to discard with the packaging…) and operating manual.

The ‘Cube’ has its altitude axis passing horizontally though the upper 1/4 of the cube, with a Vixen style dovetail receptacle on one side and a clutch/lock knob on the other. The Azimuth axis is similar to other GOTOs in as much as it rotates on its base. The base is marked in one position with ‘South’. (more on this later). Below the altitude friction lock knob there are ports for the std hand controller, a remote controller, 12Vdc in and an on-off switch. These all turn with the upper part of the mount, so cord wrap is a potential issue if you are not using the batteries. The user manual hints at this possibility, but doesn’t explain it, and the firmware version (8402) on my mount did not match the manual’s menu structure.

There is a battery access door which reveals a tray which takes 8 x ‘AA” batteries. There is an optional AC adapter available to provide 12Vdc from household current.

The tripod is a fairly flimsy affair. Even allowing for the fact that the spreader was missing, I cannot say that it would have dramatically improved matters. The larger upper part of the tripod legs are only 1” and they reduce down from that on the lower half.

After testing the tripod without the spreader, I decided it was hopeless and adapted a tripod from an old CG1 mount I had lying around.


Setup is straight forward. Spread the tripod, plunk the ‘Cube’ on top, thread the center hold down bolt up through the base, and install the spreader on the lower half of the bolt, plug in the controller and you’re done. It can be done in under 2 minutes.

The whole setup can be easily carried outdoors in one piece without any heavy breathing.

After deliberating on the wisdom of trying to use the iOptron tripod without a spreader, I decided to mount the ‘Cube’ on the tripod from my aforementioned CG1 mount, which by comparison, is quite substantial. Some may cry foul, but I can assure you that the ‘Cube’ benefited from this upgrade. I understand from various user groups that the tripod is one of the first upgrades available from iOtron on their more expensive mounts.

Loosening the Altitude lock allows easy tube balancing by sliding the OTA back and forth in the dovetail. No balancing is necessary in the Azimuth axis.

Get the base as level as possible by adjusting the tripod legs. There is a bubble level built into the mount’s base.

As mentioned, the default set-up position is the mount facing south (base is marked ‘South’), and the tube has to be pointing vertical. This vertical orientation is critical to the alignment and function of the GOTO but it is all but omitted in the instruction manual. (It is mentioned in passing once on page 5.)

Powering up.

Load the 8 x ‘AA’s, plug in the hand controller and hit the ‘On’ switch and the controller lights up with the iOptron logo, firmware version number and serial number. Following soon after that is a busy 8 line LCD red backlit screen (adjustable brightness) showing a bewildering array of information. However, the bits that matter are ‘GPS On’ which shows that it’s searching for a GPS lock which will change to GPS ‘OK’ when it has a valid GPS lock. This usually happens within 10-20seconds where I am. As a check, the date and your local time should show on the bottom line. On the right hand side of the display about half way down are shown the selected slew speed. (1 thru 9)

From this home screen, you press the ‘menu’ button and the next screen looks a bit more familiar. Here you can choose various Setup, GOTO and Utility functions just like any other controller.

The controller needs some getting used to. The buttons need a firm press with a lot of travel and they cannot be pressed too quickly, otherwise the controller cannot keep up and you will undershoot or overshoot your intended selection. I suggest that you enable the key beep so you know when you have a good input and when you don’t

The slew speeds need to be toggled through – you cannot select a specific speed directly. For example, if you want to go from the max slew to the next slower one, you have to cycle thru the 8 other speeds to get there..

Because the controller does not have a number key pad, all selections within the menus typically involve incrementing or decrementing the on-screen values via the up/down – left/right arrows on the controller. You will spend a lot of time looking at your iOptron controller.


The controller provides the usual options of a one or two star alignment. The mount works best if you are dead-on level and the tube is dead-on vertical (use a spirit level). Although ultimately, this should not matter for a 2 star alignment, it is critical for a reasonable 1 star alignment and for putting the selected alignment stars near the FOV in 2 star mode.

In 1 star mode, you will choose a star and be prompted to move the mount via the hand controller to center and then accept that star. The mount then starts tracking from then on.

In 2 star mode, once you select your first alignment star, the mount will slew to where it ‘thinks’ the star is, which, if you setup carefully, will not be far off. This is helpful if you are not good at remembering some of the more arcane star names…. Once the first star is centered and accepted, the second star is selected and providing you chose a star that the controller wants, it will then slew there and be pretty close too.

I say ‘a star that the controller wants’ because it only provides a limited selection, and it separates them into east and west groups (as it turns out). If your first alignment star was in the ‘east group’ it forces you to choose a star in the west group as your second alignment star. Although this ensures adequate separation for a good ‘map’, there is no mention of this in the manual and you have to be looking at the controller to notice the brief message that flashes up for a second or less prompting you for this requirement. And if you don’t know the location of the stars in the ensuing short list that follows, you’re out of luck and will have to start over. If, like me (and the owner before me), you have various obstacles blocking your view (houses, trees, ect..) , a 2 star alignment may not even be possible given the star selections presented.

I have had the ‘Cube’ out on several successive nights trying to figure it out, and have not yet been able to get a good a good enough alignment for the GOTO to work accurately.

General performance.

I have not been able to get the Cube to place targets any closer than the somewhere in the FOV of my Celestron 6x30mm finder. The scope used for these tests was a Celestron C5/F10 SCT. This would give it a FOV almost ½ that of the Short Tube refractors that iOptron sells as a package with their mounts. On an F5 or F6 scope, this level of accuracy would probably put it somewhere in the FOV of a 25mm Plossl.

This is fine for bright objects that you can see in the finder (in which case you don’t need a GOTO mount), but of limited value for dimmer objects. After a GOTO you typically have to carefully sweep up/down and back and forth to locate your target. For the uninitiated, not seeing anything in the eyepiece is as good as a miss, and for the more experienced trying to find dimmer objects, not being sure if it is actually in the FOV or not is an unnecessary frustration.

Once an alignment has been performed, the mount starts to purr away quietly in tracking mode. Slews at max rate are not objectionably loud (quieter than my LX200), but slower at 5* sec.

When you sync on an object in an attempt to improve the pointing accuracy in that locale, ensure you first choose ‘Sync to Target’ from the menu before centering the object and pressing ‘Enter’. If you center first and select ‘Sync to target’ second (as with other GOTOs), the mount will sometimes start a run-away slew. The manual does not mention this. Syncing seems to have little affect on the accuracy. For instance, following a two star alignment on Alphertz and Albiero, a GOTO to Vega did put VEGA at the far edge of the FOV of a 25mm EP. But a subsequent Sync on Vega did not allow the Cube to find M57 just at the other end of Lyrae.

Sometimes after a GOTO, the mount will ‘cog’ up and down. Doing a Sync to Target cures this. Also, after a GOTO, the controller will beep when it finishes the slew. Occasionally, the mount will ‘hiccup’ immediately after the beep and jump up a degree in Altitude. It is easy to bring back with the controller keys, and does not seem to affect the tracking, but it is an additional annoyance.

I noticed that the slew speeds in AZ and ALT are not the same.

Tracking, once aligned is so-so. Objects will drift out of the FOV in about 2-3 minutes.


iOptron rates this mount as being good for 7-11 pounds depending on the length and diameter of the OTA. I think these are overly optimistic values. My C5 OTA tips the scales at 6lbs, and is probably as compact a scope as you can hope to find in the 5” aperture range, so even though it is less than the lower end of the recommended maximum, it is straining this mount despite the use of a heavier tripod. The previous owner was trying to swing a C6 OTA and found it was unworkable despite still falling within the official 7-11 lb range.

Fine focusing requires a very gentle touch, and the focuser on my C5 is really smooth and light. Vibrations will damp down in about 2 seconds but heavier or longer scopes, or scopes with tighter focusers would be a real chore.

I would hazard that this mount would do best with a 70-80mm short tube refractor or 90mm MAK – something that is short and keeps the OTA’s axis closer to the mount.

The User manual

The user manual weighs in at 35 pages. Pretty good until you realize that only 14 of these pages actually deal with the mount. The rest is filler material. (Terms, definitions, messier, star and constellation lists, ect…)

The manual tells you what all the functions are called, but not what they do or how to use them, and certainly, mentions none of the caveats that I encountered and mentioned above.

If it sounds like I’m a bit negative on this product, you are right. I had high hopes, but overall, found the product unnecessarily disappointing. For the price of the ‘Cube’, you could afford to buy a good used CG5 or Vixen Polaris mount (albeit not with GOTO), that would provide a much sturdier platform for someone new to Astronomy. And I’m a firm believer that a good mount is more important than a good OTA.

In the aperture class that this mount is capable of swinging, most of the targets will be difficult to locate even IF the GOTOs place the target in the FOV.

The Cube has the potential to be a really good little mount (within its limits) if some of these issues can be addressed. iOptron now has a heavy duty edition of this mount called the Mini-Tower with a heavier payload capacity and sturdier tripod.

What’s to like

Light and portable

What’s to dislike

Sparse Manual
Quirky controller operation
Limited payload
Flimsy tripod
Glitches in the firmware
Questionable performance

In closing, I realize that there may be many Ioptron cube owners that have got theirs to perform well, or have not experienced the problems that mine presented. Maybe my firmware needs updating, maybe I have a Monday model.

But here’s the thing. This mount is aimed at the budding new-comers to our hobby. These new comers won’t know to sweep for targets if the GOTO doesn’t deliver, or use averted vision to increase their visual acuity. They may not want to go through the hassle of trying to update the firmware. So after a couple of nights of frustration, they will feel that they just can’t get the hang of it and Astromart will see another Cube up for sale (maybe mine), and our hobby loses another recruit.

And that’s a shame.