You will be sleeping in your sleeping bag every night, a mummy bag is the warmest and lightest and what we recommend. A thermarest, is necessary (NEO AIR). A full length is the most comfortable, but a ¾ length will also work. For sleeping at night, you want a headband or stocking cap to sleep in. Sleeping in a set of long underwear will keep your bag cleaner and it will be easier to face the morning cold. For a pillow, We generally put my Down jacket in my stuff sack or a pillowcase.
Synthetic vs. Down -- if you won’t be using a sleeping bag very often and/or are worried about getting it wet, then buy a synthetic. One of the most popular synthetic fills is Polar guard 3D -- Mountain Hardware, Sierra Designs, North Face, Go Lite, Marmot & Moonstone make good bags. Prima loft and Lite loft are also good. Snug Pacs by Gun Accessories and Lamalite by Wiggy’s are two other synthetics to consider. A decent synthetic will cost $150-300 dollars.
If you use your bag a lot and want the best, buy a Dry loft Down Bag with 700 - 800 fill quality down. They will cost around $400-500 but will last much longer. The best down bags are the Western Mountaineering Kodiak, Apache & Antelope Super Dry loft. North Face, Feathered Friends, Mountain Hardware & Marmot make some excellent down bags also. We run the Stone Glacier -15 and love it!
A 15-25 degree type bag will work well for August and early September.In later September a bag rated somewhere between -- 10 to 15 degrees would work. If you want one bag for all seasons, get a bag in the -- 5 to 10 degree range. A lightweight, summer/early Fall Synthetic Mummy bag will weigh 3-4 lbs. A heavier, late fall, bag will weigh 4-6 lbs.; down is generally ½-1½ lbs. Lighter than a synthetic of the same temperature rating.
If you use your bag a lot, purchase a silk liner and you won’t need to wash your bag as often. To care for your sleeping bag when at home, leave it in a loose bag (many of the good bags come with one) or hang it in your closet.Keeping one in a stuff sack breaks down the loft. But on the hunt it is mandatory, you don’t want your sleeping bag to fill your whole pack. You will need a waterproof stuff/compression sack for your hunt. OR (Outdoor Research) makes one called the Hydro seal that is excellent (this is what we recommend). Granite Gear and Integral Designs also make great compression sacks (recommended to keep bulk down). If you’re worried about getting your bag wet, you can line the stuff sack with a plastic garbage bag before stuffing. The “OR” stuff sac we use is water proof.