For groups of two looking for a lightweight backpacking tent with decent elbow room, the choice of lightweight backcountry shelters can at times seem limited. The category can be narrowed down to just a few contenders quite quickly, with one of the leading candidates being the topic of this review, the venerable Six Moon Designs Lunar Duo. A single-walled shelter offering 34 square feet of interior floor space, the Lunar Duo offers a nicely adequate floor plan for 2 or luxury for 1. This is a welcome change compared to many other “2 person” offerings on the market, most of which are really simply large 1 person tents and a tight, mostly unlivable squeeze for 2.

Not only does the Lunar Duo serve up more interior room than most competitors, it also includes 2 side entry doors and two huge vestibules at 12 square feet each. All of this at a space to weight ratio that few 2 person mainstream tents can match. Beginning back in 2012, the Lunar Duo is offered in both silnylon and polyester fabric versions. In this review we’ll discuss both models and feature our experiences with the predecessor to the lighter “Explorer” silnylon offering as well as the Explorer itself.

Lunar Duo Design

To save weight, the tent uses the two trekking poles that you’re hopefully already carrying for support (set to 45”). If you’re not a trekking pole user, Six Moon Designs (SMD) offers a carbon fiber pole (you’ll need 2) that can be purchased separately. Trekking pole user or not, every Lunar Duo comes with a pair of short, curved Easton aluminum spacer poles that are inserted into an interior sleeve sewn into the roof on each side of the tent during setup. An elastic pouch secures the poles in place and the result is a ceiling that peaks into a smooth curve rather than the sharp, angular roofline of many tents. As a result, headroom is greatly increased. A minimum of 6 stakes are required for setup. 6 additional tie-outs surround the tent – offering a greater amount of wind resistance if needed. Line tensioners are included for each of the 6 main stake points. Stakes are not included – SMD offers stakes for purchase separately for the tent or if you prefer, you can assemble your own set. This adds a silver lining to the potential drawback of the situation – you can assemble a package that best suits your needs with any of combination of stakes that you wish. We found that a setup of MSR Ground Hogs along with shepherd’s hook stakes work best for this tent.

There are two versions of the Lunar Duo, the lighter and more expensive Explorer Lunar Duo (30d silnylon) version ($395), and the 1 lb. heavier but cheaper $210 Outfitter version (190T Polyester). Either way, the canopy of the tent protects the occupants nicely from wind driven rain, overlapping the inner living space significantly on all sides. Dual zippered doors offer each person an easy entry and exit through the large vestibule on each side. Each vestibule secures to a hook that slides down the side guy line using a prussic knot. This allows the user to slide the vestibule up and down for more views and ventilation, or farther down for greater weather protection. If desired, you can also enter and exit the tent this way (by simply sliding the vestibule upwards), though you’ll have to duck a bit lower than if you fully unzip the vestibule to exit.

Once unzipped, SMD provides a loop and toggle system that allows you to roll each side of the vestibule up and secure it to the main tent body. This allows for the best views and ventilation in good weather, and the easiest entry and exit. In practice we found ourselves mostly deploying the vestibule at night and simply sliding it up the line and down to enter and exit. A peak vent on each side of the tent assists with ventilation. At first glance they look as though they might be penetrated by a driving rain, but in practice they functioned well. They are located in the vestibule section, so even in a worst case scenario the living quarters wouldn’t be affected.

A full enclosure of ultralight no-see-um netting completes the Lunar Duo’s design, resulting in complete protection from crawling and flying insects. A pocket is sewn into the netting on each side for storage of essential items. For the floor you’ll again find 30d silnylon in the Explorer and 190T Polyester for the Outfitter. The floor is shaped to create a bathtub design with generously sized sidewalls all around. At 54” wide by 90” long, the floor plan is quite generous as well. 45” of headroom allows even taller hikers to sit up comfortably – and since the roofline isn’t sloped side to side, this full height can be used by both occupants. 6 guyline points are included surrounding the tent for additional stability if desired, guylines not included.

The packed size is 15” by 6” with a 20” circumference. Seam-sealing is required – you can either opt to DIY with a tube of seam-sealer or SMD will take care of the process as a $35 option. One great thing about the design is that there are no seams to seal on the floor - and overhead you’ll find a seamless sheet of fabric as well until you reach the head and foot end of the tent where the insect netting is sewn in. Basically, while sealing is still required, it’s not quite as critical as other lightweight shelters where seams are running directly over your head and underneath your pad.

Unfortunately, while SMD expanded their Lunar Duo lineup in 2012 with the more affordable & 1 lb. heavier Outfitter model, we were also hoping they’d go the other way as well and release a lighter cuben fiber model to round out the lineup. SMD previously released the now discontinued Refuge X 2 person tent in cuben / Dyneema Composite Fiber, and recently they’ve begun to release solo models as well as 2 person tarps using the superlight but strong material. So far, no word on Dyneema Composite Fiber for the Lunar Duo, but we’re keeping our fingers crossed.

The Lunar Duo offers ample space for 2 hikers, plus a bit more especially when at least one shorter sleeping pad is used.

In Practice

Setup

The tent takes approximately 5-10 minutes to setup, and is about as easily done with 1 or 2 people. While the instructions call for spacer pole insertion prior to pitching the tent, this involves reaching into the living quarters to insert the poles. The tent has a lot of fabric, and we found at times it could be difficult to make sense of all that nylon while inserting the poles. Additionally, opening up the inside of your tent to the elements in rainy weather is obviously not ideal. We found that pitching the tent first and inserting the spacer poles later worked fine and was more convenient. The tent also works pretty well without the spacer poles, but you’ll lose headroom.

The spacer poles are made from Easton aluminum and weigh 2.6 oz. for the pair. We found that it was best to pitch with the vestibules closed – otherwise you might end up with a bad main guyline angle that won’t allow you to close the vestibules (easily fixed with a quick re-stake). Another tip is set the main guylines just slightly to the left of each vestibule zipper – this allows the silnylon flap that lays over the zipper for additional rain protection to lay flat. One complaint is that this flap snags easily on the zipper when the vestibule is not taut. However, due to the slippery nature of silnyon, it’s a pretty quick and easy fix.

Space & Livability

The tent is very spacious. Not only is there room for 2 full size inflatable sleeping pads, there is enough room to fit both in with extra space between the pads and again on each side. The floor is also quite long at 90 inches, so you’ll have quite a bit of additional room at the head and foot end as well. On top of all that, each vestibule has enough room to store a full pack out of the elements, yet still allow space for an easy entry and exit. The tent was quite large enough for the two of us plus our 50 lb. 4-legged hiking companion and our gear. The canopy significantly overlaps the interior on all sides – so even if you find the foot of your sleeping bag pressed up against the netting of the tent for example, you’re still well protected from rain and splash. While the footprint is large, we’ve used the Lunar Duo in everything from old growth forests to alpine environments and so far, we’ve never had an issue finding a spot to setup camp.

The Lunar Duo offers ample vestibule storage on 2 sides.

Support System

With this much space, we found that a taut pitch was needed for good stability in windy conditions. Trekking poles, due to their extreme stiffness and strength helped a lot in this regard – really allowing you to tighten things down while maintaining the roofline. We also tested the optional carbon fiber pole set that SMD offers for those who aren’t trekking pole users. At $80 per pair at 3.6 oz., the price is on the steep side but lighter than trekking poles. The poles worked in practice and I wouldn’t hesitate to use them for most trips. However, to really tighten up the tent so much downward force is exerted from top to bottom that the carbon poles begin to bow. This didn’t cause any problems and the poles never broke, but to some extent it was still disconcerting. Still, the poles held up great in 20-30mph winds and do an adequate job, but don’t quite inspire the same confidence as trekking poles. You can also opt for a pair of cheaper aluminum poles for $30 per pair at 6 oz.

Wind, Guylines, & Stakes

Trekking poles or not, we highly suggest using the optional tieouts to increase stability. The Lunar Duo offers a single tieout at both the foot and head end as well as a tieout on each side of both vestibules. For maximum wind resistance, all tieouts should be used but we found this to be overkill even in very windy alpine camps. In the interest of saving weight, we found the best method for dealing with wind was to pitch one vestibule into the wind, then utilize both tieouts on that (the windward) side only (less guylines and stakes). We used 5’ of 3 mm utility type cord for our extra guylines, combined with a lineloc type tensioner to make tensioning a little easier (the 5’ length is greatly reduced after it’s looped through a lineloc and tensioned). If you’d like to be able to easily switch between sides, you can attach these with a loop to loop connection or simply always pitch that side of the tent into the wind. Using micro linelocs and a thinner line could save some weight, though a loop connection probably wouldn’t be ideal (could be hard to remove after being under tension). Since our experience is with the silnylon version where sag is always a factor, we permanently attached tieouts of the same length and again with a lineloc to the head and foot end of the tent.

This helps a bit no matter which way the wind is blowing but also ensures that the tent stays off the foot of your sleeping bag (or head) if the tent begins to sag due to moisture in the middle of the night. How many of these tieouts to use definitely depends on personal preference and conditions. For maximum stability use them all, or none if you expect still & dry weather or don’t mind a bit of shiftiness when the wind picks up. I found the method above to be the best all-around balance and kept things stable enough in 45mph gusts, the highest we experienced in the Duo. If it’s a bit too drafty inside, you can even lower your trekking poles a bit and batten the shelter down all the way to the ground, but at the cost of ventilation and headroom. The extra tieouts do great with lightweight shepherd's hook stakes, though for the 4 corners and especially the two main guylines running under each vestibule a stake with better holding power like the MSR Ground Hog was preferred.

Rain & Humidity

The Lunar Duo offers great protection from rain – due to the overlapping canopy rainstorms are of little concern and with all that space and headroom, being tent-bound due to weather isn’t such a bad thing. Vertical sidewalls prevent rain from entering during entry and exit. One issue inherent to all silnylon shelter designs is sag – especially when wet and the Duo is no exception. After setup, we found that a quick re-tension of the guylines was required after an hour or so after the fabric had a chance to stretch. SMD makes it pretty easy however, with tensioners at each corner allowing you to cinch things up without having to re-stake and a lineloc for the side guylines that you can even re-tension from inside the tent. When setting up your tent, loosen each of these lines to allow for maximum tightening later, and if you’re using linelocs for your extra guylines this is quick work as well. Generally, this was sufficient to keep the Duo taut until the next morning, however if humid or rainy weather rolled in you’ll again be faced with the need to tighten things up – at which point the tent should maintain its pitch well until you’re ready for departure.

When we declined to venture out due to the weather in the middle of the night however, the tent never sagged so much that it became a huge problem, though some head & foot room would be compromised and wind resistance would also be affected. The polyester Outfitter model should have much less of an issue in this regard. Condensation inside the tent was also a concern, although always just a nuisance and only during humid weather. Whenever possible, sleep with the vestibules raised for maximum ventilation to counteract the issue. Both cases were combated with the occasional wipe down of the interior roof fabric using a pack towel and even at the worst, the DWR shell of our sleeping bags was enough to keep us warm and dry – although if you're experiencing a high condensation night, you’ll want to keep the shelter tight for clearance so you aren’t rubbing the foot of your sleeping bag against a damp ceiling as you sleep.

The Lunar Duo is a 3-season shelter but we ventured into snowy conditions on more than one occasion. While a light dusting of snow is of no concern, if more than an inch or so is expected to fall a shelter offering more snow load support would be recommended. The 30d sil floor of the tent does have the potential to leak under high pressure if you were for example, to kneel on the floor over wet ground. We always used a lightweight polycro groundsheet underneath (mostly to extend the life of the floor) and never had any issues with water seeping in from below. Even without a groundsheet, you should be fine as long as you’re not setup on extremely soggy ground and placing high pressures (knees, elbows, etc.) on specific parts of the floor.

Modifications

Floor

I decided to make a few very small modifications to our Lunar Duo. First and foremost was a seam-seal treatment for the floor that we think most everyone will find quite an asset. Stock, the floor is quite slippery and if you’re setup on any type of incline (which seems to be almost 100% of the time for spots I pick) you’ll soon find you and your sleeping pad slowly sliding downhill. Setting up the tent at home, a seam-sealer set of stripes, dots, or patterns of your choice across the inside of the floor will greatly help in this regard.

Vestibule Attachment

There are two webbing loops that SMD has attached to the end of each vestibule. Attaching these loops onto the hook attached to the main guylines allows you to slide the vestibules up or down and secure them tightly when needed for weather protection. We began to find this attachment process cumbersome – the loops are large and the opening of the hook small. Attaching the loops and removing them was tedious, especially when you were leaning out of the interior of the tent at night, trying to attach each loop to secure the vestibule for potential bad weather rolling in. The solution was to tie 4 lengths of 3 mm cord to the each webbing attachment point, essentially forming a new loop that is much easier to attach and detach when needed. With the hook under tension, there is no risk of an accidental disengagement.

Adding loops of cord to the vestibule attachment system greatly improved the vestibule securing process and disengagement.

Zipper Pulls & Corner Tieouts

No zipper pulls were included with our Lunar Duo. The addition of glow in the dark paracord pulls makes life just a bit easier in the darkness. We also elected to tie a double knot at the end of each corner tieout – forming a nice handle for quick one-handed re-tensioning.

Changes Compared to Older Lunar Duo Tents

Models

Starting in 2012 SMD streamlined the Lunar Duo line while adding a lower cost option made from Polyester fabric. The Explorer is now the silnylon Lunar Duo, and comes in at a pound lighter but $185 more than the Explorer. Offering a lower cost version of such a well-designed tent is a great idea especially where pack weight might not be the largest concern. Even at 57 oz. however, the Outfitter is still pretty light when you’re looking at the 2 person tent market as a whole.

Floor

Previously, the Lunar Duo had two floor options – an “Ultralight” as well as a “Standard” option. The ultralight option was made from 30d silnylon with the standard floor utilizing a 70d fabric with a 4 oz. weight difference between the two. For 2012 the 30d “Ultralight” became the standard and only option on the Explorer with the 70d floor eliminated from production. There were pros and cons to both options. We tested the ultralight option in our pre-2012 model. Our reasoning behind this was that even with a lightweight polycro groundsheet; this combo came out lighter than the standard floor with no groundsheet…and it’s easier to replace a cheap groundsheet than an entire tent floor. One benefit the standard floor had is that its tackiness was built in, so the anti-slide floor treatment we described earlier was more of an option than a necessity and the floor was waterproof to a greater degree than the 30d, now standard floor.

Zipper, Fabric, & Color

Gone these days is the classic bright green color option, with the Lunar Duo now made only in the more subtle grey or olive colors depending on availability it seems. Though we never had any issues with the zipper of the previous version, it’s now been beefed up to a sturdier #5 version, which does seem to result in a slightly smoother action as well. Corner tieouts and other various points around the tent have been more heavily reinforced and the silnylon has also been upgraded to a more premium & waterproof fabric on the Explorer version compared to the pre-2012 models. According to SMD, this new fabric is a substantial improvement and offers approximately twice the waterproofness / hydrostatic head rating compared to the previous models. In our opinion, this is a huge selling point. We only experienced slight misting (where the intense pressure of the rain is enough to result in an extremely fine mist through the fabric and into the tent) in the older Lunar Duo in the heaviest of rains – resulting in a small nuisance rather than a problem. The new fabric should make an already great shelter that much better. In our testing, the fabric did indeed offer a very significant increase in waterproofness compared to the older model.

Modified vestibule attachment system in use

Admittedly however, our older model has seen significantly more use. With these changes, the weight of 2012+ redesigned Lunar Duos went up to a listed weight of 41 oz. (currently up again to 45 oz.), where previously the tent was listed at 39 oz. with the 30d ultralight floor (all weights prior to seam-sealing). You’ll also find a small change in the way the arch poles secure into their sewn-in roof sleeves – instead of a Velcro closure, they now secure with an elastic & pouch arrangement. SMD has designed a flap of silnylon that overlaps the vestibule zipper when closed and taut. One new welcome addition for 2012 is an additional Velcro securement point halfway up the vestibule just to help keep the flap in place over the zipper and offer some additional rain protection for whatever you have stored underneath each vestibule for the night. After seam-sealing the new model, we did find a few more loose thread ends vs. the original model and the new reinforced corner tieouts exhibited some thread stress / cutting through the fabric on each corner after our first pitch. We seam-sealed these areas a bit more heavily and so far, so good. One final point was that while our doors were opposing on the older model, the doors are now in the same position side to side.

Specifications

• Pre-2012 LD Weight After Seam-sealing & Anti-slip Floor Treatment with Spacer Poles in Stuff Sack: 40.5 oz. (No Stakes)
• 2012 LD Weight in Stuff Sack w/ Spacer Pole Prior to Sealing: 41.1 oz. (Listed Weight: 41 oz. – Current Listed Weight: 45 oz.)
• After Sealing in Stuff Sack with Spacer Poles: 43.4 oz.
• Carbon Fiber Poles: 3.6 oz.
• Aluminum Poles: 6 oz.
• 3 mm Guylines w/ Linelocs .3 oz. each
• Polycro Groundsheet: 2.8 oz.

Seam-sealed new Lunar Duo

Conclusion

Time after time the Lunar Duo has met our expectations, kept us dry, and kept our packs lighter compared to alternative traditional shelters offering this much space. The space to weight ratio is impressive and for groups of two it’s hard to compete with so much livability. Each person has their own door. Each person has their own vestibule capable of sheltering their gear from the elements. Inside, there’s still a lot of elbow room and you don’t have to draw straws to see who gets the short side – the high roof treats all occupants equally. Over time the shelter has been upgraded with a more waterproof fabric as well as had changes implemented to increase durability, increasing the overall weight slightly. We never had any issues with durability using the older version, so we have mixed feelings about the changes. On one hand, the heavier zippers and more reinforced corner tieouts just seem like more weight in our mind.

On the other hand, it’s hard to argue with a fabric upgrade resulting in a more waterproof product – so for us that aspect is a definite bonus. During wet and humid weather, condensation is there and will need to be managed. Like all silnylon shelters, you’ll probably have to re-tension the Explorer model once or twice to get the perfect pitch. However, the drawbacks are workable in practice and didn’t result in any major headaches.

You can find the Lunar Duo Explorer Tent here at Six Moon Designs and find the heavier but cheaper Lunar Duo Outfitter here. You can also find both tents available here at Amazon.com. For more on backpacking tent features and considerations, see our guide on how to choose a backpacking tent.

Editor's Note: This review originally appeared in Issue 3 of TrailGroove Magazine. Read the magazine article here for additional photos, pros and cons, and our Lunar Duo rating.