Every computerized GoTo begins with a calculation. Your telescope mount knows where the Andromeda Galaxy is supposed to appear because it knows the date, the time, and where on Earth you're observing. Give it the wrong longitude, or set the clock an hour off, and the sky the computer calculates may no longer match the one above your head.
The iOptron 8438 external GPS module takes care of much of that information automatically. Its 32-channel GPS receiver obtains your geographic coordinates, date, and time from GPS satellites, then passes that information to a compatible iOptron mount.
For owners of the CEM26 and GEM28, it's a convenient upgrade that eliminates much of the manual setup associated with entering time and location. For CEM40 and GEM45 owners, the same module serves as a replacement for the GPS receiver originally supplied with those mounts.
It's particularly useful if you regularly travel between observing locations. Whether you're setting up at home, visiting a dark-sky site, or attending a star party several hundred miles away, the GPS receiver helps make sure the mount begins with the correct location and time information.
One Module, Two Different Purposes
iOptron designed the 8438 for four specific mount families, although its purpose depends on which mount you own.
CEM26 and GEM28: These mounts use an optional external GPS receiver. Without one, the observer enters the date, time, and geographic coordinates through the Go2Nova hand controller. The 8438 supplies that information automatically after acquiring satellite signals.
CEM40 and GEM45: These mounts were supplied with GPS capability. The 8438 can be used as a replacement module if the original receiver has been lost, damaged, or otherwise requires replacement.
The module is not advertised as a universal GPS accessory for every iOptron telescope mount. Before ordering, make sure your mount is one of the supported models.
How the GPS Connection Works
The 8438 includes a straight-wired 6P6C connection cable. On the CEM26 and GEM28, the cable connects the GPS module to the mount's iPORT connection.
Once the mount is powered, the GPS receiver begins searching for satellite signals. The Go2Nova hand controller displays GPS ON while the receiver is acquiring the necessary information.
When the satellite connection is established, the status changes to GPS OK. The mount can then update its time and geographic coordinates using the information received.
Acquiring satellites normally takes a few minutes, although the time required depends on reception conditions and whether the receiver has recently been used in the same area.
According to iOptron's instructions, the external receiver may be disconnected after the hand controller displays GPS OK and the necessary information has been acquired.
There's no need to install a separate computer program or connect the GPS receiver to a laptop. The module communicates directly with the compatible telescope mount.
What GPS Does and Doesn't Do
A GPS receiver makes the initial setup process more convenient, but it doesn't automatically polar align the telescope or guarantee perfect GoTo pointing.
The module supplies geographic coordinates and accurate time information. That helps the mount calculate where celestial objects should appear from your observing location.
You still need to set the correct time-zone information in the Go2Nova hand controller. The UTC offset and daylight-saving setting are not automatically determined by the GPS receiver.
For example, if the hand controller is set for daylight saving time when your location is actually observing standard time, its displayed local time may be wrong by an hour even though the GPS has received the correct satellite time.
Proper polar alignment is also necessary for an equatorial mount to track the sky accurately. A pointing or star alignment may be needed to improve GoTo accuracy, depending on the mount and the observing procedure being used.
The 8438 eliminates a common source of setup errors. It doesn't replace the mechanical alignment procedures that make an equatorial mount work properly.
Under the Night Sky
GPS becomes particularly useful when you take your telescope away from its usual observing location.
If you set up in the same backyard every evening, the coordinates stored in the hand controller may remain correct for months or years. Once you've established your location, there's little reason to enter it again unless something changes.
But astronomy has a way of encouraging travel. A darker location an hour outside the city may reveal nebulae and galaxies that are difficult to observe from home. A star party in another state might provide the opportunity to photograph objects you've been planning for months.
At a different location, the mount needs the new geographic coordinates to calculate accurate pointing information. Forgetting to update them can leave you wondering why the telescope isn't finding objects where you expect.
With the 8438 connected, the mount can acquire the location automatically once a suitable satellite signal is available.
It's a small convenience, but one that can make repeated setups a little more enjoyable.
Observing Tip: Check for GPS OK
When using the 8438, give the receiver a reasonably clear view of the sky before beginning your alignment procedure.
GPS signals are relatively weak, and roofs, buildings, dense tree cover, and some metal structures can interfere with reception. If the receiver has difficulty acquiring satellites, try placing it where it has a clearer view.
Watch the Go2Nova hand controller for the GPS status. GPS ON means the receiver is still acquiring satellite information. GPS OK confirms that the connection has been established.
Before beginning your first GoTo, take a moment to check the displayed time, UTC offset, daylight-saving setting, and geographic coordinates.
iOptron specifically recommends setting the daylight-saving option correctly rather than manually adding or subtracting an hour from the displayed time.
If the GPS cannot establish a connection, you can still enter the necessary information manually and use the mount normally.
A few seconds checking the setup information can save a surprising amount of time troubleshooting an inaccurate first GoTo.
Know Before You Buy
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For four mount families. iOptron specifies the CEM26, GEM28, CEM40, and GEM45.
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Optional upgrade or replacement. Adds GPS to the CEM26 and GEM28; replaces the GPS receiver on the CEM40 and GEM45.
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Time-zone settings remain manual. Check the UTC offset and daylight-saving setting in the hand controller.
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Satellite reception is required. The receiver needs a sufficiently clear view of the sky to acquire a GPS signal.
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Does not replace polar alignment. Accurate equatorial tracking and GoTo pointing still depend on proper mount setup.
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Connection cable included. The complete 8438 package contains a straight-wired 6P6C cable.
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No computer necessary. The receiver communicates directly with the supported mount.
What's Included
- 1x iOptron 32-channel external GPS module (#8438)
- 1x Straight-wired 6P6C connection cable
Telescope mount and hand controller are not included. This listing is for the complete GPS module and cable package.
FAQ
- Will the 8438 work with my CEM26 or GEM28?
- Yes. The 8438 is an optional GPS accessory for these mounts and automatically supplies time, date, and geographic coordinates after establishing a satellite connection.
- Does my CEM40 or GEM45 already have GPS?
- These mounts were supplied with GPS capability. The 8438 is intended as a replacement for their original GPS receiver.
- Do I need a computer to operate it?
- No. The GPS module connects directly to a compatible mount using the supplied 6P6C cable. Satellite acquisition and status information are handled through the mount and hand controller.
- Does it set daylight saving time automatically?
- No. You must still configure the hand controller's UTC offset and daylight-saving setting correctly. The GPS provides the time and geographic location, but it doesn't determine your local civil-time rules.
- How do I know when the GPS is working?
- The Go2Nova hand controller displays GPS ON while satellite data is being acquired and GPS OK once a successful connection has been established.
- Will it improve my GoTo accuracy?
- It can eliminate pointing errors caused by incorrect location or time information. Proper polar alignment and any necessary pointing calibration remain important for accurate GoTo performance.
- Can I use the mount if GPS reception is unavailable?
- Yes. The necessary time and location information can still be entered manually through the hand controller.
Final Thoughts
The iOptron 8438 isn't an accessory that changes how your telescope moves or how much detail it shows. Its job is much simpler: make sure the mount starts an observing session with the correct time and location information.
For someone who always observes from the same backyard, that may not seem particularly important. But for an astronomer who frequently visits different dark-sky locations, automatic GPS setup removes another little task from an evening already filled with equipment to assemble and align.
For CEM26 and GEM28 owners, the 8438 is a convenient addition. For CEM40 and GEM45 owners, it provides a direct replacement option for the original GPS receiver.
Connect it, let the receiver acquire its satellites, confirm the settings, and get on with the more interesting part of the night.
