Introduction
The Outdoor Research Stargazer AscentShell Bivy (18.9 oz / 536 g, $259) is of interest to alpinists, backpackers, and bikepackers because it is one of the few waterproof-breathable bivy sacks on the market that weigh just over a pound, has a side-entry zipper, and also includes mosquito netting and a headroom-extending pole.
About this Review
This review of the Outdoor Research Stargazer AscentShell Bivy is a Limited Review.
A couple of years ago, I started engaging in one or two-night winter backpacking trips, mainly in the White Mountains of NH. I first started with four-season tents, but the weight of those was around 5 lbs (5.25 kg) or more. Then I had a couple of overnighters in my winterized hammock. I was extremely satisfied with this setup considering its warmth, comfort, lack of condensation, and ease of entry and exit. However, I noticed that when heading to unknown locations, particularly in the Whites, sometimes finding the right trees took longer than expected.
I started thinking that a waterproof, breathable bivy may be the solution to unsatisfactory camping spots.
When using a bivy, if you have enough room to lay or, worst-case scenario, sit, then you have a place to sleep. We find ourselves in these locations typically in the summer, and so the mosquito netting and wide opening of the Outdoor Research Stargazer AscentShell Bivy are desirable when compared to other offerings.
I tested the bivy at Mount Washington State Forest in MA. Â Conditions ranged from cold and dry (below freezing) to 44 F (6.6 C) with winds above 15 mph (24 km/h) most of the night (the maximum was 22 mph / 35.4 kph). I also had ample opportunity to test the Outdoor Research Stargazer AscentShell Bivy in rain ranging from drizzling to extended downpour.
Features and Specifications
- Enlarged head area
- Side entry
- Mosquito netting
- Two stake loops
- One guyline loop
- Fully taped seams
- Stuff sack (4 in x 4 in x 12 in / 10 cm x 10 cm x 30.5 cm)
- Fabric: Ascentshell 3L, 100% nylon, 20D mechanical stretch ripstop face with 100% polyester 12D backer, 100% nylon, 40D ripstop with TPU lamination floor
- Weight (claimed): 18.9 oz / 535 g
- Weight (measured): 19.6 oz / 555 g (bivy 17.3 oz / 490 g, pole 1.8 oz / 51 g, stuff sack 0.5 oz / 14 g)
- Dimensions (claimed)
- length – width at the top – width at the bottom): 82 in – 26 in – 19.5 in / 208 cm – 66 cm – 49.5 cm
- Dimensions (measured)
- length – width at the top – width at the bottom: 77 in – 25 in – 19 in / 195.5 cm – 63.5 cm – 48.2 cm
- Bathtub floor with a height of 2.75 in (7 cm)
- Waist-length #3 zipper with a 1 in (2.5 cm) stiffened storm flap plus a second 3 in (7.6 cm) flap on the hood
- Overhead pole sleeve and volumizing pole. The pole is 52.3 in (132.8 cm) in length. Once inserted, the base of the created arch is 29.3 in (74.4 cm), and the peak height is 18 in (45.7 cm)
- Â The length was measured along the right side, from the pole sleeve to the footbox seam. The width at the top was measured 5 in (12.7 cm) lower from the left pole sleeve and the bottom width was measured about 10 in / 25.4 cm from the footbox. Both measurements were made from floor seam to floor seam, not including the bathtub floor seams.
Performance Analysis
Since this is a Limited Review of the Outdoor Research Stargazer AscentShell Bivy, a detailed performance analysis based on long-term use will not be presented. Instead, performance observations and issues are noted below.
| Criteria | Observations and Issues |
|---|---|
| Waterproofness | The Outdoor Research Stargazer AscentShell Bivy is constructed of two different fabrics: a proprietary waterproof breathable 3-layer top fabric labeled AscentShell and a TPU laminated floor. As usual, the seams are taped. The cut of the bivy includes additional seams to form a 2.75 in / 7 cm tall bathtub floor of sorts, which effectively raises the #3 zipper off the ground. The zipper is well guarded against vertical water ingress. The top half is protected by a 1 in / 2.5 cm stiffened storm flap. Additionally, a second 3 in / 7.6 cm flap protects the other half of the zipper as it comes around to form the hood. While the OR website does not publish any waterproofness numbers, in my experience, the fabric is waterproof. The water I found inside the bivy after my testing (some of which included intense rainstorms) was either the result of condensation or made its way in through a zipper opening. I like leaving a roughly 6 in / 15.2 cm opening in the zipper as close to my mouth as possible. I have observed that spindrift and rain will splash my face on windy nights when laying on my back and leaving the opening at the apex. The solution for both situations was turning on my side and/or moving the opening to the side of the bivy. |
| Breathability / Air Permeability | The OR website does not publish any numbers on breathability or air permeability. At around 0 F (-17.8 C) , I did not experience much condensation in the bivy. The bivy was dry to the touch. Although my sleeping bag felt moist in my lower legs it was not enough to make my hands wet. It was certainly not wet enough to wring any water from the bag, nor wet enough to make my feet cold at night. At around 45 F (7C) and all night rain, once again, my footbox was slightly wet. It was nothing I could wring out and nothing that manifested itself in any way while sleeping. But this time, I could feel the wetness in my hand when brushing the bag. Based on my experience, the amount of moisture felt similar to what I experienced before in GoreTex bivies (military one and older Outdoor Research model) as well as the Montbell Sleeping Bag Cover. (See Compared To…) |
| Warmth | The bivy definitely provides an increase in warmth. On one testing evening, the night time forecast called for lows around 10 F ( -12.2 C). I brought my Enlightened Equipment Enigma 20 F (-6.7 C) down quilt, hoping that the bivy would suffice. And if it did not, I was planning to wear my down jacket and down pants to supplement. At the 9:30 p.m., the temperature was 15 F (-9.4 C). I decided to wear my down puffy jacket to bed, but I felt the pants were unnecessary. When I got up at 7:30 a.m. the next morning, I noticed it was much, much colder than the forecast had anticipated. My backpack thermometer bottoms out at 0 F (-17.8 C), so I could not tell how cold it was. When my partner sprung out of his hammock at 9 a.m., he said the temperature was -10 F (-23.4) based on his thermometer. At around 45 F and rainy, I ended up using a 100 weight fleece vest draped over my torso to supplement my Enlightened Equipment Revelation 40 F (4.4 C) down quilt. Experience tells me that the bivy was also trapping a significant amount of heat. In those conditions, I would typically use a 30 F (1.1 C) bag or additional clothing to supplement the Revelation quilt. |
| Comfort / Roominess | See Commentary |
| Packability | The original stuff sack that comes with the Outdoor Research Stargazer AscentShell Bivy allows it to pack into a 12 in x 4 in x 4 in (30.5 cm x 10.2 cm x 10.2 cm) package without much compression. My preference with bivies is to stuff them at home the night before leaving for a trip by inserting the pad and quilt or quilts into the bivy and then roll them into the bottom of my pack. This approach speeds up deployment and entry in case mosquitos or precipitation are a concern at bedtime. For my winter outing, I was able to stuff the bivy + Thermarest NeoAir Xlite Regular (72 in x 20 in / 182.8 cm x 50.8cm) + Enlightened Equipment Enigma regular length and wide width 20F/-6.7 C into a bundle measuring 12 in x 7 in x 7 in (30.5 cm x 17.8 cm x 17.8 cm) without much compression. This is a really compact winter shelter setup, which, combined with a 0.5 in (1.3 cm) closed cell foam pad under the bivy, allowed me to sleep warm at nighttime temperatures below -10F (-23.3 C). |
Commentary
What makes the Outdoor Research Stargazer AscentShell Bivy Unique?
The fabric of the Outdoor Research Stargazer AscentShell Bivy provides the expected breathability and waterproofness. The mosquito netting and wide zippered opening allow its use in a wide array of conditions. Users who place their sleeping pads under the bivy will find the Stargazer AscentShell Bivy offers incredible performance. Users shorter than 6 ft (183 cm) in height or who have medium torsos who wish to place their sleeping pads inside will probably be equally happy. As I stated above, the Stargazer AscentShell Bivy can pair with other gear to form an incredibly compact cold-weather sleep system.
That being said, my biggest drawback is the Stargazer AscentShell Bivy’s size. My preference is for sleeping pads inside the bivy, which users of long or wide pads will struggle with. Having said that, I see myself using the Outdoor Research Stargazer AscentShell Bivy when air traveling in three seasons to locations with low night-time temperatures and the chance of evening/night-time rain. In particular, when visiting rocky areas with little room for tents. Its light weight, small packed size, and the option to have full protection when in a semi-seated position make it ideal for such trips.
Here are some of the features that I paid particularly close attention to while conducting my Limited Review.
- Waterproofness and Breathability
- Roominess and Comfort
- My Wishlist
Waterproofness and Breathability
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Companion forum thread to: Outdoor Research Stargazer AscentShell Bivy Review
The Outdoor Research Stargazer AscentShell Bivy (18.9 oz / 536 g, $259) is one of the few waterproof-breathable bivy sacks on the market that weigh just over a pound and also includes mosquito netting and a headroom-extending pole.
Nice, iago! Â I realize this is a limited review but you put a lot of detailed information in there. Would you say the half-moon space beyond the footbox seam is too small to put a stuff sack with your shoes/ boots in during below-freezing temps? Â Thanks!
Dear Greg, thank you for the compliment!
Regarding the half-moon shape at the foot end, it’s too small for footwear storage. I would probably store something I do not need to access throughout the night and I want out of the way, such as a water filter, powerbank/batteries, or similarly sized items.
Users with a similar body size to mine or larger could struggle fitting footwear inside. The best storage area in the bivy is at the head end, where it is relatively generous–certainly in comparison to the rest of the bivy body.
I personally prefer to store footwear outside, but if I had to store footwear inside the bivy, I would probably put it at the head end separating both pieces of footwear and/or perhaps incorporating one or both into my pillow system…
<p style=”text-align: left;”>As pointed out several times in the review, bivy’s are a tough sell to us backpackers.</p>
<p style=”text-align: left;”>For a small to no weight penalty, you can get a good 1+ person (higher cost) Dyneema tent that has room for your gear and you can sit up and layer up without compression in cold weather. Â For warm weather, it makes more sense to carry a 6-8 ounce (+stakes & lines) flat tarp at less cost.</p>
I took this bivy on the Colorado Trail this summer and LOVED my choice. I had a very limited time window to complete the trail and was alone, so it was absolutely perfect for me. I am 5’10” and slim, used a OV mummy pad and a 30 degree EE Enigma, and had no problems with filling the bivy up even when on my side. If necessary I could pull all my gear inside in the head space, which made it pretty tight, but more often I left my pack and shoes outside in a compactor bag. It was light and small in my pack, waterproof in the rain, allowed me to watch the stars (probably my favorite feature), and allowed me to hike much later into the day, not worrying about finding a good campsite or having enough light- as long as I wasn’t on the side of a cliff, I could find a spot to set up. In the mornings I could unzip, set up my stove and make a hot breakfast while my always cold toes were still cozy in my bag, then pack up in a matter of a minute or two and hit the trail. Loved it! Disadvantages were: basically no living space if there’s precipitation, no room for a dog. Otherwise, a perfect shelter for this trip and for solo trips to come!
Stargazing from 12,000 ft up can’t be beat, especially when all you have to do if it starts raining on you is a simple zip. I can’t think of another fully waterproof, one pound backpacking shelter that lets you see the whole night sky.
Dear Terry, I agree that for most people in most circumstances a tent, tarp or hammock is an easier choice. However, bivies are one more option with its own set of pros and cons, just like any other shelter. At times bivies shine, others not so much. As James above points out, they can be a supreme choice for many of us for certain trips :)
Thank you for a very detailed review. Very well researched.
I’ve used the prior OR model, the Helium Bivy on backpack outings in the desert and the Sierras. I thought it performed quite well in the desert. Freestanding, with minimal stakes. And resistant to fine wind-blown sand when the top is zipped shut. And great for stargazing the desert sky at night. I would expect the new Stargazer bivy to also perform well in those conditions.
I had very mixed feelings about the Helium Bivy performance in the Sierras. I had significant condensation issues when the temperature dropped into the low 20’s. Comparing specs, the Stargazer uses a different material. That may explain the much better cold weather breathability that you saw.
After my cold weather experience with the Helium, I bought a Dyneema tent for other fall weather mountain trips. It is only slightly heavier than my bivy. But I plan to take the Helium bivy the next time I go back to Arizona. The experience of others on the Arizona trips was that fine wind-blow sand can blow right through mesh screens. And the multiple stakes required to set up the tent can be a chore in sand. For a free standing, sand proof tent, the solutions I’m aware of are 3 pounds or more.
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