The first thing that I always do is research the other photo forums and check for repair/durability issues. I've seen good and bad with both the Tamron and Sigma 150-600. I would definitely stay away from the Sigma 120-300 2.8. Lensrentals.com had to repair their copies of the lens about every 14 weeks. I owned a Nikon 200-500 5.6 for all of about 16 hours before returning it to B&H for focus issues. The lens would constantly hunt in less than ideal light.

I bought a 300 2.8 G VR I in mint condition from a store in Japan for $2600. Tack sharp, incredibly fast focusing, great in low light, and performs well with the 1.4x and 2x teleconverters. You then have a 300 2.8, 420 4.0, and/or a 600 5.6 for about $3000. A good used Nikon 200-400 VR I will run you about $1900-$2600, but like another post said, some are sharper than others.

Saving money is great (I buy all my equipment used), until that equipment doesn't work or delivers sub-par images. Then how much have you really saved?

We lived in southeast Alaska for three years (Haines). My daughter still lives in Sitka and my sister in Haines. My mother is up there now.

What equipment to take and whether or not to take a cruise versus the ferry all depend on you. As far as excursions being crowded, that's true if you go on a cruise ship sponsored excursion. Not true at all if you charter your own adventure.

Those who recommend the ferry have a point. You have a lot more time and you see more ports. On the other hand it doesn't have the luxury, and many people end up sleeping in the viewing area chairs or in tents on deck. If that isn't your thing then don't take the ferry unless you have planned your entire itinerary and have booked a cabin for all trips.

As for equipment that depends on your shooting style, your fitness level and your willingness to leave some equipment behind in your cabin from time to time.

There will always be wildlife. Maybe not bear and maybe not whales, but always wildlife. There is the possibility of sea otters, sea birds, river otters, deer, mountain goats and if you are lucky moose, although they aren't particularly common where you are going.

Alaska can be shot with wide angle, trying to show as much of the scene as possible, or it can be shot with a big lens isolating a small area. Some wildlife can be shot at 200 to 300mm, but if wildlife is your thing you are going to want a bigger lens. A 200 isn't going to cut it if you have a chance to shoot a bald eagle fishing.

Those who say travel light have a point. I might travel light on an excursion, but I always bring as much gear as I can safely carry on a trip. You may never use a lens or tripod or whatever, but if you don't have it and need it you will regret it later. You can leave most of your gear in your cabin and just take what you need for the activity that you are doing when you are off ship.

If money is no object then I would get a wider angle lens and the Sigma 150-600 sport. Waterproof, and well built. Also pretty sharp.

The last time we visited Alaska I took a 12-20 dx lens, a 24-70 f2.8, a 70-200 f2.8, a 150-500 sigma (the 150-600 hadn't been made yet), two dslr bodies and a waterproof point and shoot camera.

We went snorkeling, kayaking, kayaking, and chartered a boat to sightsee without anyone else other than the captain. If I had it to do again, I might also take a helicopter ride.

I know that a couple of people have posted that there isn't much to see on the inside passage. I disagree, Every time you are in sight of land there is the possibility of a beautiful sight. And the scenery is constantly changing.

If you want to shoot waves crashing on the rocks then you are going to want a big lens. If you want to shoot flying sea birds then you want a big lens. If you go on a wildlife tour then you will want to have access to a big lens.

As far as whales, you may indeed get to close for a 150-600, but that isn't true for any of the other wildlife.

Ketchikan has some nice totem poles in a park. Juneau has access to Tracy Arm and Mendenhal glacier. Icy straights can be gorgeous depending on the weather. My sister and her husband often commercial fish near there and some of their photos are spectacular. Hubbard glacier can be shot with either a wide angle or big lens, depending on style. Lots to see or do. Take the equipment that suits your style and fits your budget and quit worrying about what other people think. Only you know what equipment works best for you.