Review of the iOptron "SmartStar-E GO TO Alt-Azi Mount"

Lots of people have talked about the iOptron Smartstar-E mount but judging from the order number we got (less than 50), few have actually bought them. The mount caused a big stir because it's so cheap--$200. Not surprisingly, it's also cheaply made.

The mount arrived double boxed. Other internet reviewers have stated that due to packaging confusion in China some early units were single boxed. The box had no logo and was missing the manual and AC power adapter. This isn't that big a deal because the manual is available online, the mount is reasonably intuitive to setup and can be powered with 8 AA batteries. We e-mailed iOptron requesting the AC adapter and they promised to send us one. We later discovered that the power socket is identical to the Celestron plug, so one can also power the SmartStar-E using Celestron cords.

The mount is quite easy to assemble, and the process takes only a few minutes. Our sole source of confusion was that the battery compartment door had an extra piece of plastic that apparently got stuck to it during manufacturing. After a brief examination, we gently twisted it off.

Excited, we turned the mount on. It started beeping, and the screen showed half of an iOptron logo. We took all the batteries out, tested them with a multimeter, discarded a suspect battery and replaced it. After this, the mount worked acceptably, though we continued to have minor power problems with the mount (more on this later).

We first assembled the mount during the day and put a Stellarvue Nighthawk Next Generation 80 mm (SV80ED) refractor on it. The SV80ED is about 6 lbs without mounting hardware. The mount uses the relatively standard Vixen style dovetail system but mounts the telescope horizontally, which takes some getting used to. Also, it lacks a lock screw that some other mounts use to provide additional security for the dovetail plate. Adapters that allow you to mount equipment with 1/4-20 camera screws on the Vixen style dovetail plate are readily available.

We immediately noticed that the mount is quite wobbly and has a good deal of play especially in the azimuth axis. At higher powers, there is noticeable vibration in the eyepiece during focusing. We would later find that this makes high power night time focusing very difficult.

The mount has 5 different slew speeds: 2x, 8x, 64x, 256x and MAX. We calculated that MAX slewed at about 5.3 degrees per second on the azimuth axis or approximately 1200x. At the higher slew speeds the mount's motors resemble the "blender motors" of the CG-5. At lower speeds or during tracking they make odd chirping sounds that are much quieter but can be mildly disconcerting to the user.

We pointed the telescope at a terrestrial target and started using the hand controller. The manual describes a night time alignment procedure in which the scope is pointed straight up and the south arrow on the mount pointed south, but because it was daytime, so we ignored this procedure. We played with the mount's daytime landmark goto system with which the user can save a terrestrial landmark and instruct the mount return there at some point in the future. Initially this procedure worked extremely poorly. We power cycled the mount, rebalanced the telescope and oriented the telescope vertically as instructed. We then saved a goto point again and this time, it did indeed return to the saved position. Thus, we believe that to use the daytime landmarks feature, you must start with the tube in the vertical position.

Also, during the daytime we discovered that the handcontroller has noticeable lag in motor commands. Both changing the slew speed and commanding motion with the arrow keys has about a one second lag. We should note that this is *not* backlash compensation. The motors will not start running until significantly after the arrow key is pressed. Likewise, they will not stop running until significantly after arrow key is released. The lag in changing motor speeds causes the user to push the [Speed] button several times in succession, believing that his initial button push didn't register. This may cause the him to cycle past the speed he desired and force him to  cycle through all the speeds.

We also noticed some minor user interface bugs in the hand controller. For example, while the handcontroller requests your coordinates and the local time, it incorrectly computes the offset from UTC time to your time zone. In California, we are 8 hours behind UTC, but it believed us to be 8 hours ahead. Also, when asked to return to its initial park position, the display say that it is at "Part Position". However, the hand controller does have good brightness and sounds controls that let you turn off its pesky "button pushed" beeps and adjust its backlight. The screen is large with four vertical rows of text and uses menus that are similar to a computer or DVD player user interface.

The Orion/Synta AZ-3 is a common  $150 manual Alt-Az mount. Both axes are geared with slow motion controls, but it can also be pointed roughly by hand. Although it is much maligned on some telescope forums, namely because it has problems observing near zenith, the authors have found it to be a sturdy, reliable, lightweight, portable and simple mount for small telescopes in the sub-7 lbs weight range, the same weight range targeted by the SmartStar-E.

We tested the SV80ED and an Orion Apex 102mm Maksutov Cassegrain on both mounts. The Apex is slightly lighter at 5 lbs and has a significantly shorter tube and thus a lower moment of inertia about the altitude axis. We later used this scope for our night testing.

For both scopes we found that that the AZ-3 is significantly superior in terms of stability. The AZ-3 can hold these reasonably lightweight scopes stable up to their diffraction limited powers with little to no visible vibration. Focusing on the AZ-3 is far easier than the SmartStar-E due to the lack of vibration. We also found it to be easier to use to visually find objects in the AZ-3 because the scope can simply be pushed to the target.

Obviously the AZ-3 lacks the tracking and computerized control of the SmartStar-E, but it is worth noting that for the observer who is strictly interested in a cheap Alt-Az mount to visually find objects, there are cheaper and better manual options than the SmartStar-E.

We tested the SmartStar-E at night. We had already carefully input the time and location of the mount. We followed the mount's setup directions, orienting the south arrow away from the North Pole (using Polaris as North) and starting with the optical tube pointed toward the zenith.

The mount supports both one and two star alignment procedures and advises that if the mount is not level, the one star alignment will probably not suffice. We used the two star alignment. The two star procedure requires one star to the west of the meridian and one to the east of the meridian. Annoyingly, after setting up the first alignment star, the hand controller does not filter out other stars that are on the same side of the meridian, it simply complains when you select them. This is also a problem when trying to go to celestial objects that are not up.

After the alignment, our goto results were less than stellar (pun intended). Even after a sync command to a nearby star the mount often fails to put objects in or near the field of view of a wide field eyepiece with approximately a 1 degree true field of view. In our opinion, this is a major problem with this mount. One main selling point of the SmartStar-E is goto. Its official name is the "SmartStar-E GO TO Alt-Azi Mount" (capitalization theirs). However its gotos are so inaccurate that a common, long focal length telescope in its designed weight range cannot center the requested objects. While we do not know the causes of this problem for certain, we can speculate that encoder resolution, deformation in the plastic gears (more later), clutch slippage and the general flexibility of the mount and tripod are partially responsible for these goto inaccuracies.

Although the goto accuracy is at best suspect, the tracking accuracy is surprisingly good. We found that objects stay centered quite well, with drifts amounts that are better than acceptable for visual observers. Keeping an object in a high power eyepiece should be no problem for any telescope in the weight range supported by this mount.

Unfortunately, focusing on planets and other high power objects is extremely painful. Every focus adjustment induces vibrations in the mount and forces the observer to wait for several second before examining the results. This makes focusing excruciatingly slow and difficult and takes the fun out of high power observing. Also, mild taps to the mount or bumping the legs may not only induce vibrations, but remove the centered object from the field of view of a high power eyepiece. This is particularly a problem for high planetary observing when swapping in eyepieces or cameras causes a previously centered object to disappear. This can be quite frustrating. Overall, we would rate the mount's stability and tracking performance to be on par with or perhaps slightly better than an Orion/Synta EQ-1 GEM with motor drive.

The hand controller is easy to use due to its large screen and menu based interface but, it does take a some time to get used to using the arrow keys for object selection; it doesn't have numbers. Generally objects are arranged either numerically or alphabetically and in all cases numbered. For instance, if you are browsing a list of star names, Acamar is #1 and Zosma is #189. You navigate by selecting digits of the number with the left and right arrow keys and changing the digits with the up and down arrow keys. So, if you wanted to go to Deneb, you might change the second digit to quickly get near the D's and then use the first digit to find Deneb. Though initially somewhat confusing, this is far faster than other systems where you have to scroll through all 189 named stars just using the up and down keys.

Lastly, we had some power issues with the SmartStar-E while on battery power. Whenever the mount begins to slew, the screen darkens, probably because the batteries cannot supply enough instantaneous power to meet motor demands. In and of itself this is nothing more than a mild nuisance. However, we later found that the batteries deplete rather quickly and that once they do the mount ceases tracking or responding to motor commands on the hand controller. Fortunately, the mount uses the same 12V plug as Celestron equipment and can thus be used with their 12V AC and car adapters. We also verified that it will run with fully charged 1.2 V NiMH rechargeable batteries which some users may prefer because the mount appears to deplete batteries rather quickly.

Curious about the general operation of the mount and the instabilities in the axes, we removed the plastic cover that protects the altitude axis. It revealed a complicated plastic gear system that ultimately turns a worm gear. The plastic worm gear is actually quite large, and has approximately 80 teeth.

The altitude arm is connected to connected to the worm gear through a simple friction clutch. The user tightens a metal knob on the altitude axis that forces a plastic part on the altitude arm to come into contact with the plastic worm gear. Should too much, or for that matter, a reasonably small amount, of force be exert on the altitude axis, these two plastic parts will slip without any danger of damage to the drive system.

While we are glad that the altitude axis is well protected, we find the amount of force needed to cause this clutch to slip surprisingly small. The altitude axis is the more stable of the two axes but we wouldn't be surprised if the plastic gears and clutch design are responsible for some of the play we have observed in the mount.

We did not attempt to access the azimuth axis as this would have required us to disassemble much of the mount.

We can also comment on the construction of the rest of the mount. The tripod legs are 1" stainless steel and a plastic eyepiece holder/leg spreader is provided. The legs are reasonably sturdy, though definitely not up to the standards of the legs on higher end mounts. We should also note that the legs do not extend as far as legs on other mounts, making observing near the zenith a challenge.

A surprisingly large amount of the construction of this case is metal. The only external plastic parts are the colored side plates. The mount also comes with a bubble level whose accuracy we did not test. We would have preferred a mount with a plastic case and a metal drive system to the reverse.

When the Yugo was introduced, some pundits stated it was what a car made by Bic would be like. The same is true of this mount--it seems like it was made by Bic.

At $200, the SmartStar-E is the cheapest goto mount on the market and clearly targeted at an amateur on a budget. It is 1/3rd the price of a CG-5 or LXD-75 GEM and 1/4th the price of a Vixen Skypod, the sole other standalone Alt-Az goto mount of this variety that we know of (though some Celestron Nexstar Alt-Az telescope systems use a Vixen style dovetail so their mounts could also be used for other scopes).

Its single largest defect is its poor stability. In this sense, it is considerably inferior to cheaper manual Alt-Az mounts such as the AZ-3. Focusing at high powers is frustratingly difficult as slight touches excite massive vibrations. A gentle push to the azimuth axis produces noticeable movement to the naked eye, even when the mount is tracking.

We also find the goto system to be inaccurate, but the tracking performance to be more than adequate. We noticed that there are several software and user interface glitches such as slow hand controller response. The handcontroller screen is generally simple and intuitive to use and the large screen makes for a more user friendly experience.

We think this mount is generally best suited for astronomers with a limited budget and a light wide field telescope whose large field of view is used for observing low to medium power objects. In these cases, the mount's instabilities and the inaccuracies of the goto system will hopefully be less important. Although the mount advertises weight capacities up to 11 lbs, we believe that 7 lbs or so is the realistic top limit due to the mount's wobbliness. Due to its light weight and low cost, it is also well suited for a travel mount.