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Reviews > Sleep Gear > Sleeping Bags > Therm-a-Rest Altair bag > Owner Review by Ray Estrella

Therm-a-Rest Altair Sleeping Bag
By Raymond Estrella

February 18, 2013


NAME: Raymond Estrella
EMAIL: rayestrellaAThotmailDOTcom
AGE: 52
LOCATION: North Western Minnesota, USA
HEIGHT: 6' 3" (1.91 m)
WEIGHT: 225 lb (102.00 kg)

I've been backpacking for over 30 years, all over California, Minnesota, and many western states. I hike year-round in all weather, and average 500+ miles (800+ km) per year. I make a point of using lightweight gear, and smaller volume packs. Doubting I can ever be truly ultralight, I try to be as light as I can yet still be comfortable. I start early and hike hard so as to enjoy the afternoons exploring/chilling. I usually take a freestanding tent and enjoy hot evening meals. If not hiking solo I am usually with my brother-in-law Dave or my twin children.

The Product

Manufacturer: Therm-a-Rest.Altair bag
Web site:
Product: Altair Sleeping Bag
MSRP: US $489.95
Size: Long
Year manufactured/received: 2013
US temperature rating: 0 F (-18 C)
(See web site for all the EN ratings)
Weight listed: 42 oz (1191 g)
Actual weight: 42.1 oz (1193 g)
Stuff sack weight: 1.1 oz (31 g)
Color: Blue
Amount of fill: 23 oz (640 g) of 750+ fill power goose down
Baffle height/loft: 3 in (7.5 cm)
Loft observed on top: up to 3.5 in (8.9 cm) between baffles
Packed size listed: 8 (diameter ) x 18 in (20 x 46 cm)
Actual packed size: 8.3 x 16.5 in (21 x 42 cm)
Image at right courtesy of Cascade Designs

Quick & Dirty, Nitty Gritty

The Therm-a-Rest Altair Sleeping Bag is a very interesting take on sleeping bag design. Cutting needless weight with an aggressive variable fill ratio and making a bag that works for side-sleepers and back-sleepers alike the Altair is a pleasure to use. The EN Limit rating is closer to true than the stated US rating in my opinion. Please read on for the details.

Product Description

The Therm-a-Rest Altair Sleeping Bag (hereafter referred to as the Altair or the bag) is the warmest offering in the company's new line of sleeping bags and sleep systems.

The outer shell made of dark blue 30 denier nylon ripstop with a DWR (durable water repellent) finish. The ripstop pattern is probably the smallest I have ever seen. (I needed to use a magnifying glass to verify that it was indeed ripstop, but then again these eyes are getting old ;-)

Looking at it from the top.

On the top right of the shell near the hood the bag's name and rating along with the Therm-a-Rest logo is embroidered. On the other side is a small zippered pocket that can be used to store a watch or cell phone close enough to hear an alarm go off.

The hood of the Altair is of the flat style (as opposed to the hood-type popular right now). This is to make it more comfortable, indeed possible, for side sleepers. A drawstring with tethered cord-lock works very well to pull it into a very good hood for back-sleepers.

The bottom of the bag boasts an anatomical footbox. Well, for back-sleepers anyway. Attached to the shell at the end of the footbox are a couple tags. One is the standard consumer tag, with fill type, weight, materials, and "Made in China". The second, smaller tag has care instructions.

The down is placed in horizontal chambers separated by baffles made of 4-way stretch mesh. The baffles are spaced apart every 4 in (10 cm).

The bag has a 2-way, grey nylon YKK zipper running 3/4 of the length of the bag. It sits very low on the bag from the lower end to just shy of shoulder level, then the zipper curves in and climbs to its ending point at the side of the hood. The zipper is placed on the left side of the bag, the only side offered for the Altair at this time. The zipper tabs have nice big pulls attached to make it easy to slide them in the dark.

Backing the zipper inside of the bag is a huge 4 in (10 cm) down filled draft tube to keep cold air out. It can be seen in this picture of the inside of the bag.

hood and draft stops

The lining is made of grey 30 denier nylon. It is a bit stiffer and courser than I am used to feeling for linings. Running around the inside of the bag at shoulder level, is a fat 3 in (7.5 cm) diameter insulated draft collar. It has a drawstring and cord lock on the right side of the bag, away from the zipper. As it is just below the hood's cord it is easy to find. There are four loops inside the Altair which are for drying inside out, and for possible optional liners or other gear down the road.

Look at my bottom

Flipping the bag over exposes a couple more features of the Altair. Two wide elastic loops are called SynergyLink Connectors. These keep the bag attached to the sleeping pad. But this is not just to keep it from sliding off; it also keeps the bottom insulation under the sleeper. Which is quite important as the Altair uses the sleeping pad to provide most of the bottom insulation of the sleep system. It needs to as the Altair uses the most aggressive variable fill ratio I have encountered yet in a traditional sleeping bag. Only 15% of the down is placed in the bottom/back of the bag, but this is in the oval area seen above, which is where the bag will be lying flat on the pad. Therm-a-Rest calls this Zoned Insulation. This cuts weight by focusing the fill on top where it is needed. But proper pad choice is very important since pretty much all of the r-value needed to insulate the sleeper from the cold ground is going to be provided by the pad.

To further accommodate side-sleepers the Altair has been constructed allow the bag to move vertically while still staying attached to the pad. This lets shoulders and hips be vertical instead of spread out flat like back-sleepers have, but does not compress the down by pulling the bag tight at these spots.

Stuffed and stored

Finally the Altair comes with a stuff sack and a two-tiered mesh storage sack as seen above.

Field Data

Once the ground froze and winter set in I took the Altair on eight backpacking trips. Five were on the Red River on private property north of Halstad, Minnesota, one was on the North Country Trail by the Anoway River in Chippewa National Forest, one on the North Country Trail in Paul Bunyan State Forest, and the last in Smoky Hills State Forest where I camped near the Shell River. These trips were cold with lows averaging around -5 F (-21 C). The trip on the Anoway River saw -22 F (-30 C). Here is a picture of my campsite in Paul Bunyan State Forest.

On the NCT

I also spent a night in my yard the day after a storm that brought very low temps. (I could not get out of town as the roads were a mess.) The low was -24 F (-31 C) with 58% humidity.


First off let me talk about myself and sleeping bags. I am a toss-and-turn side-sleeper. I wake up to turn over about once or twice an hour through the night and always sleep on my side. So I can't snug closed the hood on a sleeping bag unless that bag is going to be turning with me. Modern sleeping bag design has seen even fill ratios go the way of the Dodo so I have always taken a bag rated to the next colder temperature of what I expect to see.

With an average of 3 in (7.5 cm) of loft on the top of the bag (where it is most important) I can't agree that this hits a 0 F rating for me. No matter how I shake it out and let it sit I don't see enough loft. My other bags and quilts at this rating have between 3.5 to 4 in (9 - 10 cm) of top-level loft. From what I feel in the field, and what all my sleeping gear notes show me, this sleeping bag's rating for my sleeping style should be right around 10 F (-12 C). This actually jives with what the EN Limit rating for the Altair is listed at. (12 F/-11C) There is a lot of room in the chambers. Maybe switching to a higher fill power of down plus adding a few more ounces it would bring it to an actual 0 F rating for me. Now that said, this could well be fine at the stated temp for a back sleeper that can get the most benefit from the hood.

I found the Altair to be very comfortable. It was not tight across my shoulders at all. It really does work well for side-sleepers. While I could not pull the hood too close, the inside draft collar worked great. It really held the heat in well. In fact on my coldest night I even had to vent it. I slept outside at -24 F (-31 C) using the Altair along with a Therm-a-Rest Alpine Blanket as an over-bag. Around 1:00 AM I woke up to find that I was sweating. I loosened the draft collar to allow some of my heat to escape. This worked well and I was fine for the rest of the night.

I used the Altair by itself for five of the nine nights of use. The low temps on these trips were between 15 and 0 F (-9 to -18 C). All use on these nights was with a Therm-a-Rest NeoAir XTherm for a sleeping pad. Because the sleeping pad provides almost all of the bottom insulation this pad, with its r-value of 5.7 is a good choice to pair with the Altair. Of course any pad with a high r-value should work too. Here is a shot of the combo described near the Red River.

On the Red

As I mentioned before when it got down around 0 F (-18 C) I was feeling cold. I have always been interested in the concept of over-bags and lately have been tweaking it with using quilts as there is no real reason to add anything to the bottom as long as the pad is sufficiently insulated. So when temps dropped low enough for Mother Nature to tell me the use-window was closed for the Altair I told her "no way". I added more insulation in the form of quilts to push my use of the Altair all the way through our harsh Minnesota winter. Half the time I used the Altair's tiny sibling, the Alpine Blanket. It is seen here before my coldest night this year.

At -24 F

The addition of this 23.1 oz (655 g) quilt lets me take the Altair way down in outside temperature. Based on my use this winter I would have no problem taking this combo to or below -30 F (-34 C). It should be noted that on these low temperature trips I add a ZLite Sol closed cell pad under the XTherm to boost the r-value to 10.4. As I use the ZLite as my sit pad and a kneel pad I don't slide it under until just before I turn in for the night. Here is a better shot of the Altair/Alpine Blanket combo on a backpacking trip along the Red River.

With over-quilt

When temps were not quite that harsh, but still lower than I could take the Altair alone I paired it with a 17.85 oz (506 g) summer quilt, the Sierra Stealth from Jacks 'R' Better. This worked great around -10 F (-23 C) but one trip saw me get surprised with a low of -22 F (-30 C) that had not been forecast. Fortunately I had a huge parka along on that trip. The Altair, over-quilt and parka are all in this shot from the North Country Trail campsite.

Chippewa NF at -22F

On roughly two-thirds of the trips I used the SynergyLink Connectors wrapped around my pad. I have to say that getting them around my large size pad is a chore. This is compounded by the fact that doing anything when it is way below freezing is a struggle. Putting them around my regular sized XTherm (now my son's) is a lot easier. The connectors work very well to keep the pad in place. I really like the way they have room for the bag to lift at the sides. To my mind this is the only way for side-sleeper to use a normal sized bag (not one extra roomy). But the other way is to just not be connected, and I did use the Altair with it just sitting on the pad, not hooked to it. Maybe my many years of sleeping bag use has me able to turn in place or something, but I did quite fine without the connectors too.

My sleeping style sees me slightly bend my legs so I end up with extra room in the bottom of the bag. Because of this there was plenty of room down there for water bottles and boot liners. My headlamp, camera, and gloves sit in the upper part of the bag with me. It's just a regular gear party in there!

The Altair handled condensation well, but it is so cold here that condensation just freezes onto things before it has any chance to soak in. Right by my face is the only place that really gets wet. But I did not see the shell get any sign of wetting out.

The zipper has been no problem. I think I can remember only once or twice having it snag while trying to make a fast exit. I never used the little pocket so can't say anything about it.

OK, how can it be better? Number one for me (borne out by my own gear purchases) is better down. There is nothing I will pay more for with no regret than high fill-power down. At 750 fill-power (which I know is nice compared to the majority of mass market retail down gear) the Altair is the lowest fill power of my 16 down items.

Number two? There is no two; I really can't find anything else that bugs me or needs improvement. I think that they have come up with a very good design and can't wait to see where it goes from here. I will leave with a shot of the Altair in my tent on my last trip in Smoky Hills State Forest. And yes, I am wearing my over-quilt… ;-)

Smoky Hills SF

This report was created with the Report Writer Version 1.5 Copyright 2013. All rights reserved.

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