This tripod primer by Tringa45 is good to read:
Requests for advice on tripod purchase are often posted on birdforum and frequently I am surprised that birders are prepared to spend large sums on a scope but try to scrimp on a tripod and head. A scope not only magnifies the subject but it also magnifies angular disturbances. With an...
www.birdforum.net
Leg diameter affects stability. In general, if the material of the tripod leg is equal thickness, then a tripod leg with a larger diameter will be more stable than a leg of smaller diameter.
When comparing tripods from different manufacturers that are made from the same material, look at the specifications for the diameters of each leg section if available.
Gitzo, Manfrotto, Benro, Leofoto all list the diameter of each of their leg sections under the technical specifications on their web site. This is a big help when comparing brands and prices. However leg diameter does not tell you how thick the wall is of each tripod leg, or how stiff/rigid the specific material and leg locks used are compared to the material and leg locks a competitor uses.
Carbon fiber tripods are popular right now. A carbon fiber tripod is not shake free. Their main advantage is shaving at most 1kg of weight off the legs. A good quality aluminum tripod that is as stable (or more stable) will cost less, but will weigh more.
Some brands were mentioned by posters above at various price points
What sets Gitzo as a top level tripod is:
- the carbon fiber is high quality and stiff
- the leg locks are rigid and hold well
- the tripods achieve the combination stiffness/rigidity with some of the lowest overall weights
- they can be repaired/rebuilt if a part breaks
Companies like Benro and Leofoto offer carbon fiber tripods that are less expensive to purchase. The trade off is that even though they are carbon fiber, when compared to a more expensive brand, they may weigh a little more, they may not be quite as rigid/stiff, and/or they may not be repairable/rebuildable.
In aluminum there are tripods like the Manfrotto MT055XPRO3 or the Slik 700DX Pro. These two tripods are pretty equal. They are both very affordable tripods from companies that have been making tripods for many years. Slik is less expensive than Manfrotto. They are tall. They are stable. They support a large scope very well. They both weigh around 2.5kg.
We have used a Slik 700DX Pro for a number of years and it has served us very well. For the price it is a great tripod. I have carried it many times on full day birding outings with lots of walking, but to be honest the size and weight were not fun. We upgraded to a couple high quality carbon fiber tripods that are just as stable, weigh less, and are smaller when fully collapsed.