kmcgreg wrote:I am unsure as to how cold to get. Comparing bags is not straightforward. The sts traverse II seems to cover the temp and weighs in around 1.2 kg. The alpine bags are all heavier and constrictive mummy shapes.
Personally, and I think many would agree, about -7c / 15F is about right for Tassie. It can get colder in some parts no doubt, but if you have good tent, good ground insulation and a reasonable array of warm clothes to use as boosters (e.g. down jacket, mid-weight fleeces) you can manage the few colder nights without much drama. A good quality bag of this rating will be a bit under 1kg.
Comparing bags is definately not easy! Do some research on down fill weights/ ratings relative to warmth (search Andy Kirkpatrick writings / blogs for one) and use that as a starting point along with En ratings. And on the choices you narrow down search for user reviews. There are a lot of good bags on the market.
Also worth carrying a vapour barrier for the cold nights if you get them. This adds a lot of warmth for little weight and preserves your down. Google 'vapour barrier sleep' and you will find lots of good discussion. Apparently this doesn't work for all (they sweat too much) but works well for me. I have one of these
http://www.extac.com.au/Adventure_Medic ... ad1138.htm, very light, serves as your emergency spaceblanket, is an emergency bivy in a pinch and is durable enough for a number of uses (at least as a liner). For more money the WM hotsac is meant to be great and is also light. Tassie has stupid weather that is generally humid and not quite freezing to just below freezing. Down suffers (loses insulating power) quickly in these conditions and the vapour barrier can help this too.
If in doubt, tend to the warmer side (IMO). Nothing to spoil your enjoyment of the bush and have you sloppy on the trail then a cold sleepless night. I doubt you'll notice the extra 200 grams of down to get a significantly warmer bag. I used to carry a -18c bag which was great - and managed to pretty warm temperatures no problem by just opening it up. But I am happy with my -7 bag now with the backup systems described above.
Lastly, not all mummy shapes are as constrictive as others but if you want to get maximum warmth for weight you want a tight fit. But again, 100g of high quality down adds a lot of extra warmth and means you can get a looser bag for equivalent if you are not too anal about weight.
Choose well - as i said before - i reckon your sleep system (other's advice about a warm mat also being critical are spot on) and tent are the most critical items you will buy. You can get away with all sorts of other crap if you get these two items right.
And please keep posting on your progress - we all love being 5 minute experts here and providing our 2c
