One of the frustrations of traveling to dark skies is deciding what equipment to leave behind. You may have a perfectly good telescope and imaging system at home, but the thought of carrying a heavy equatorial mount, tripod, counterweights, and all the associated equipment into the field can make a smaller travel telescope seem awfully attractive. Sometimes that compromise is necessary. Other times, a lighter mount with substantial carrying capacity can let you bring the telescope you really want to use.
The iOptron GEM45 is an interesting answer to that problem. Its CNC-machined German equatorial mount head weighs only 17.5 pounds (7.9 kg), yet iOptron rates it to carry up to 45 pounds (20 kg) of telescope and accessories, excluding counterweights. That's more than two and a half times the mount's own weight, and a remarkable combination of portability and capacity for a conventional German equatorial design.
The 7603A-HC package puts that mount together with iOptron's 1.75" LiteRoc stainless steel tripod, an 11-pound counterweight, and a fitted aluminum hard carrying case for the mount head. The mount also includes iPolar electronic polar alignment, GPS, a computerized Go2Nova hand controller, and internal cable management. It's a particularly sensible combination for the observer who regularly travels to a dark sky site and wants a capable equatorial mount without having to assemble a mounting system from several separate purchases.
Take the Telescope You Want to Use
One advantage of a mount with a 45-pound payload rating is the freedom to consider a substantial range of telescopes. A well-equipped 4" or 5" apochromatic refractor, an 8" Schmidt-Cassegrain, or a compact astrograph with camera, filter wheel, electronic focuser, and guiding equipment may all be reasonable candidates, depending on the complete weight and dimensions of the system.
That qualification is important. A long 6" refractor may fall within the GEM45's published weight rating yet present considerably more leverage and wind resistance than a compact optical tube of similar weight. Likewise, a telescope used for visual observing at moderate magnification places different demands on tracking than the same telescope used for long-exposure imaging at a small image scale.
The GEM45 gives you substantial capacity for a portable mount, but that capacity should be matched intelligently to the equipment. If your telescope is already a good mechanical fit for the GEM45, you may not need a separate, smaller mount merely because you're taking it away from home.
Its low head weight is especially welcome when loading and unloading the car. The mount, tripod, counterweight, and telescope can all be transported separately, leaving you with pieces that are easier to handle than one large assembled equatorial mount. The included case provides a dedicated place for the head, protecting it from ordinary bumps and handling during travel.
The Mechanics Behind the GEM45
Although the GEM45 borrows some of its lightweight construction philosophy from iOptron's center-balanced mounts, its geometry is that of a traditional German equatorial. The telescope rides on one side of the declination axis while counterweights balance it on the other. The right ascension axis is aligned parallel to the Earth's rotational axis, allowing the mount to follow celestial objects by rotating that axis at the appropriate tracking rate.
Both the right ascension and declination axes use 4.33" (110mm) diameter aluminum worm wheels with 216 teeth. Each wheel is driven by a 0.67" (17mm) brass worm through a synchronous belt transmission. The 1.77" (45mm) steel axis shafts are supported by 2.68" (68mm) bearings, substantial components for a mount head weighing less than 18 pounds.
The worm and wheel provide the fine mechanical reduction needed to move the telescope at sidereal speed, while the belt transmissions carry power from the stepper motors to the worms. The steel shafts and bearings support the telescope as its position changes during the night. iOptron has removed unnecessary bulk from the CNC-machined housing without abandoning the basic mechanical principles that make a German equatorial mount useful for both visual astronomy and astrophotography.
iOptron specifies periodic error of less than ±7.5 arcseconds over the GEM45's 400-second worm period. Periodic error is the small, repeating variation in tracking speed caused by imperfections in the worm drive. The GEM45 includes Permanent Periodic Error Correction (PPEC), allowing the owner to record a correction for the repeatable portion of that error and retain it for later observing sessions.
For demanding long-exposure imaging, an autoguider remains advisable. The GEM45 provides an ST-4-compatible guiding interface and USB computer control, allowing compatible guiding software to monitor a reference star and make small corrections while the main camera collects light. The more expensive GEM45EC adds a high-resolution optical encoder on the right ascension axis for real-time correction of periodic tracking error, but the standard GEM45 already provides the mechanical capacity and guiding connections needed for a substantial imaging system.
The 6" dual-format saddle accepts both Losmandy D and Vixen-style dovetail mounting plates, useful if you regularly change between different telescopes. Large quick-lock gear engagement levers make balancing straightforward, although the telescope and counterweight assembly should always be supported when releasing the drives.
A Substantial Tripod and a Proper Carrying Case
A lightweight mount head is only part of a good portable system. The support beneath it must be sufficiently rigid to keep the telescope steady, particularly when focusing at high magnification or recording long photographic exposures.
The 7603A-HC includes iOptron's 1.75" LiteRoc stainless steel tripod, weighing approximately 17.6 pounds (8 kg). Its steel legs, spreader, and improved leg-locking arrangement provide a substantial foundation while retaining the portability of a folding tripod.
It's worth noticing that the tripod weighs approximately as much as the mount head. That's a sensible arrangement. You can lift the relatively light GEM45 head onto the tripod without struggling with a much heavier assembly, while the supporting mass remains beneath the mount where it can help resist unwanted movement.
The accompanying aluminum hard case provides fitted foam padding around the mount head. It has reinforced exterior edges, secure latches, and a carrying handle. The case measures approximately 18" × 15" × 8.75" and weighs about 11 pounds by itself, so the head and empty case together account for approximately 28.5 pounds before any additional items are packed.
This isn't an airline carry-on guarantee or a substitute for careful handling, but it gives the mount a much better place to travel than loose among counterweights, cables, and telescope accessories. The case is intended for the mount head. The LiteRoc tripod, counterweight, and telescope travel separately.
For anyone regularly driving to star parties or dark sky locations, that organization can be as valuable as the case's protection. A mount that has a dedicated place in the vehicle is easier to pack, easier to find, and less likely to be damaged by another piece of equipment shifting during the trip.
Polar Alignment at a New Observing Site
Every time an equatorial mount is moved to a new location, its right ascension axis must be aligned with the Earth's rotational axis before it can accurately follow the sky. That is especially important for astrophotography, where small polar alignment errors can produce tracking drift or field rotation during long exposures.
The GEM45 includes iOptron's iPolar electronic polar scope built into the right ascension axis. Rather than requiring you to look through a conventional optical finder and position Polaris on an illuminated reticle, iPolar uses a small camera to recognize the star field surrounding the celestial pole.
Connect iPolar to a compatible computer running iOptron's alignment software, and the program determines where the mount is pointing relative to the pole. It then shows you how to adjust the altitude and azimuth controls to bring the axis into alignment.
Polaris itself does not have to be visible, provided enough of the surrounding polar sky remains unobstructed for the camera and software to recognize the star field. This is particularly helpful at unfamiliar observing sites, where a tree or building may block the pole star even though much of the northern sky remains visible.
The GEM45 provides a latitude adjustment range of 14° to 68° and approximately ±6° of azimuth adjustment. A broad latitude range is useful when traveling substantial distances north or south, but the limited azimuth adjustment makes it worthwhile to position the tripod reasonably close to the celestial pole before starting the alignment procedure.
A built-in 32-channel GPS receiver supplies the mount with location and time information, avoiding the need to enter new coordinates manually at each observing site. The automatic zero-position search establishes a reference position for computerized operation, and the supplied Go2Nova hand controller handles GoTo alignment, object selection, slewing, and tracking.
The hand controller has an illuminated eight-line, 21-character LCD display with a built-in heater for cold-weather use. Its database contains more than 212,000 celestial objects, so the GEM45 can be operated for visual observing without keeping a laptop connected after polar alignment.
Internal Cable Management for Long Imaging Sessions
One of the more troublesome aspects of astrophotography isn't optical or electronic at all. It's keeping the cables out of the way while the telescope moves around the sky.
A typical imaging system may have cables for the cooled camera, guide camera, electronic focuser, filter wheel, and dew-control equipment. As the mount slews or performs a meridian flip, those cables must have enough freedom to move without catching on the tripod, pulling against a camera connector, or becoming wrapped around the mount.
The GEM45 helps simplify this problem with internal cable routing and connections at the saddle end for USB 2.0, ST-4 guiding, and a 12V accessory power outlet rated at 3 amps. Some of the connections can be made near the telescope while their corresponding cables exit through the lower portion of the mount, reducing the number of loose loops hanging around the moving equipment.
The USB arrangement is a pass-through rather than a complete powered multiport hub, so a system with several USB accessories may still require a separate hub or imaging computer near the telescope. Proper cable routing and clearance checks remain necessary, but the built-in connections eliminate some of the clutter that can make an unattended imaging system difficult to manage.
The GEM45 also provides configurable meridian treatment, including the ability to continue tracking up to 20° beyond the meridian before stopping or flipping. This can be useful when an exposure is nearly complete as the telescope approaches the meridian. However, the allowable tracking angle must be checked against the actual clearance of your telescope, camera, tripod, and counterweights. The mount's electronic limit cannot guarantee that every optical tube will safely clear the support.
The GEM45 operates from a 12V DC power supply, with iOptron specifying approximately 0.6 amp while tracking and 0.9 amp during GoTo slews. Its relatively modest power consumption makes field battery operation practical, although cooled cameras, dew heaters, and computers will increase the total electrical requirements. Wi-Fi control is available through iOptron's optional iStarFi adapter.
What Owners Say on Cloudy Nights
In a detailed review published on Cloudy Nights in September 2022, Daniel Moomey described the GEM45 as a lightweight and capable mount that had become part of his regular astrophotography equipment. He reported using it with a small guide scope and PHD2 guiding software to collect five-minute exposures, with guiding performance typically in the 1 to 2 arcsecond RMS range in his particular setup.
That is an owner's measured experience rather than a specification every GEM45 will reproduce, but it provides a useful picture of what a properly configured system can accomplish.
He also discussed the mount's internal cable connections, using an external USB hub to organize several imaging accessories while keeping much of the wiring above the declination axis. The arrangement reduced the loose cables that might otherwise become tangled as the telescope moved.
For observers who regularly transport their equipment, he regarded the hard carrying case as particularly worthwhile. He also appreciated iPolar's convenience and the GEM45's ability to work with both Vixen and Losmandy-style telescope mounting plates.
His review included photographs taken with a Takahashi FSQ-85 and a ZWO ASI2600MC Pro camera, as well as a William Optics ZenithStar 71. Subjects included the North America Nebula, Rosette Nebula, and Andromeda Galaxy, demonstrating the GEM45's usefulness with compact refractors and contemporary imaging equipment.
The review wasn't without criticism. He found some of the hex-bolt adjustments less convenient in the dark than conventional knobs, and he noted that careful meridian-limit settings were important to avoid interference between the telescope and support. Those observations are useful reminders that even a capable computerized mount benefits from a familiar setup procedure and careful attention to mechanical clearance.
Under the Night Sky
The real pleasure of taking a capable imaging system to a dark sky site is discovering what the telescope can record when the background glow of streetlights and buildings is no longer dominating the exposure.
The Horsehead Nebula in Orion is a good example. The dark silhouette of Barnard 33 stands against the reddish hydrogen emission of IC 434, while the nearby Flame Nebula, NGC 2024, provides an entirely different pattern of illuminated gas and intervening dust. Under dark skies, a suitable telescope and camera can record the broader region with considerably less interference from skyglow.
For an even more demanding broadband project, consider the faint dust surrounding M81 and M82 in Ursa Major. The Integrated Flux Nebula is part of our own galaxy, illuminated by the combined light of countless stars. Its low surface brightness makes it exceptionally difficult to separate from an uneven or light-polluted sky background, and successful imaging requires careful calibration, long integration times, and favorable conditions.
The Flying Bat Nebula, Sh2-129, and the enormous, extremely faint Squid Nebula, Ou4, in Cepheus provide another ambitious project. The region spans a wide field, and the Squid's oxygen emission is notoriously difficult to record. Appropriate narrowband filters and substantial integration time are essential; simply having a larger telescope or a tracking mount won't make the subject easy.
For a smaller field, the Draco Trio of galaxies—NGC 5981, NGC 5982, and NGC 5985—offers three very different galactic appearances within a relatively compact region. The edge-on NGC 5981, elliptical NGC 5982, and face-on spiral NGC 5985 make a fascinating combination for a telescope and camera with sufficient focal length to show their individual structures.
The GEM45 is not responsible for making those objects bright. That's the job of the telescope, camera, exposure time, and observing conditions. What the mount provides is the ability to carry and accurately track an appropriately sized imaging system while those faint photons are collected.
Observing Tip: Get the Work Done Before Sunset
When traveling to a dark sky site, one of the best ways to get more useful observing time is to finish as much of the setup as possible while you can still see what you're doing.
Set up the LiteRoc tripod on firm ground, orient it approximately toward the celestial pole, and check that the legs and spreader are securely tightened. Install the GEM45 head, counterweight shaft, and counterweight according to iOptron's assembly instructions, then mount the telescope and complete the balance procedure.
Arrange your cameras, guide scope, dew heaters, and other accessories exactly as they'll be used during the night. Connect the power and data cables, verify that they have sufficient freedom to move, and check the telescope's clearance through the range of positions it will encounter during the imaging session.
Bring up the iPolar software before the sky is fully dark, confirm that the GPS has supplied the correct location and time, and have the imaging software ready. When enough stars become visible for iPolar to identify the polar region, complete the polar alignment and then establish the mount's GoTo alignment or pointing model as required by your observing software.
Before beginning an unattended sequence, run a short guiding test and inspect a few actual images for star shape and focus. It is much better to discover a loose cable or incorrect guiding setting during a brief test than after collecting several hours of exposures.
And if you expect to return to the same observing site, take a photograph of the completed setup. A simple picture showing tripod orientation, cable routing, and equipment arrangement can be surprisingly helpful the next time you unpack everything.
FAQ
- What is the difference between the GEM45 7603A and 7603A-HC?
- Both packages include the GEM45 mount head, 1.75" LiteRoc tripod, and one 11 lb counterweight. The 7603A-HC adds iOptron's fitted aluminum hard carrying case for the mount head.
- How does this differ from the GEM45 head-only package?
- The 7603A-HC includes the LiteRoc tripod and one 11 lb counterweight in addition to the mount and hard case. The head-only package is intended for customers who already have a compatible tripod or pier and appropriate counterweights.
- Does the hard case hold the complete mount?
- No. The fitted hard case is intended for the GEM45 mount head. The LiteRoc tripod, counterweight, telescope, and other equipment must be transported separately.
- Is one counterweight enough for every telescope?
- No. The supplied 11 lb (5 kg) counterweight is sufficient for some equipment combinations, but heavier or differently balanced telescopes may require additional counterweights for the GEM45's 28mm shaft.
- Can I use the GEM45 for long-exposure astrophotography?
- Yes. The GEM45 supports permanent periodic error correction, USB computer control, and ST-4-compatible autoguiding. For demanding long exposures, an autoguider and careful polar alignment are recommended. Telescope dimensions and weight distribution should also be considered.
Supplied Accessories
- iOptron GEM45 German equatorial mount head with 45 lb rated payload capacity
- Built-in iPolar electronic polar scope
- 6" Losmandy D/Vixen dual-format dovetail saddle
- Go2Nova computerized hand controller with heated eight-line LCD
- GEM45 GPS module
- 1.75" LiteRoc stainless steel tripod with accessory tray
- One 11 lb (5 kg) counterweight
- 1.10" (28mm) stainless steel counterweight shaft, 280mm long
- Fitted aluminum hard carrying case for the mount head
- Two coiled mount control cables
- USB cable
- 100–240V AC power adapter
- Quick Start Guide
Optional Accessories
Additional iOptron Counterweights: Compatible 2.5 kg and 5 kg counterweights are available for the 28mm shaft when the supplied weight is insufficient to balance your telescope and accessories.
12V Field Battery: Provides portable electrical power at sites without AC service. Size the battery for the complete imaging system, including cameras, dew heaters, and computers.
iOptron iStarFi Wi-Fi Adapter: Adds wireless mount communication through compatible smartphone, tablet, or computer software.
Guide Scope and Guide Camera: A useful addition for long-exposure astrophotography, allowing guiding software to make tracking corrections during an exposure.
Final Thoughts
The GEM45 has a great deal going for it as a portable equatorial mount. Forty-five pounds of rated carrying capacity is substantial, but a 17.5-pound head makes that capacity considerably easier to transport than many people might expect. It retains the familiar operation of a German equatorial while adding the electronic features that make a modern imaging system more convenient to use.
The 7603A-HC is the package I would consider if the GEM45 will regularly travel between home and a dark sky site. The LiteRoc provides the matched support, the counterweight gets you started with an appropriately balanced system, and the aluminum case gives the precision mount head a secure place in the car. You aren't left searching for a suitable tripod or improvising protection for the mount during transportation.
Of course, if your GEM45 will spend nearly all of its life in the backyard and you already have a safe storage arrangement, the less expensive 7603A without the case may be the more sensible purchase. The telescope and mount will perform the same way. The difference is in how you intend to live with the equipment.
For those who regularly load up the car when a stretch of clear, moonless weather appears, the GEM45 with LiteRoc and hard case offers an appealing combination. It gives you the opportunity to bring a capable telescope and imaging system to a better sky without making the mount itself the most difficult piece of equipment to carry.
