spotting scope objective??

You will most likely get alot of different answers from each individual you talk to. I just bought a swarovski spotter thats folds up to about half of its size. It has a 20 x 60 eyepiece and an 85mm lens. It is heavy but with the option to collapse it down, it fits in the pack very nicely. I think it will be ok on most hunts. If I am going in a few miles, I use the 15 x 60 binoculars mounted on the tripod. I think David Long of Eastmans uses a straight 25x leupod that I believe is a 50mm lens. I bought a leupod gold ring 15 x 30 x 50 last year that was very light weight. I think it weighs less than 2 pounds. I had a tough time with the scope as I did not like the focus adjustment on there and it seemed to fog up very easily. I took it back to the truck and carried in my KOWA spotter for the remainder of the hunt. It is a little heavier but worth taking in the extra pounds. I sold the leupold last fall. For your question however, the bigger the objective the better the view in low light situations. Another question that you may ask yourself is "what am I going to be using it for the most". Are you using it a couple of times a year to pack in and using it to spot from the vehicle the rest of the time? If so, I would go with at least a 65mm or even better an 80mm. If you are using it for packing in only then I guess it depends on how much weight you would like to carry. Hope this helps, TommyCaller

I had a Cabelas Big Sky 80mm spotter and it was ok. It was very heavy. I sold it and replaced it with a 65mm Zeiss and I am much happier now. The Zeiss is much easier to pack in as it is smaller, lighter, and shorter. I would not get another 80mm spotter. The quality optical coatings will affect the light transmission more so than the obj diameter. The field of view is more so with the 80mm but I don't see where its worth the weight.

Another reason is due to the heavier scope weight, the more sturdy the tripod has to be. This is also additional weight to pack in. I would much rather pack in more water than heavier optics.

I have a Swarovski 80 mm and it is HEAVY to lug around If I ever sell it I will absolutely go witht he 65mm instead.

I re-read your question and decided to explain something a little differently. Your pupil is somewhere between 3.5 and 6 mm across depending on the light you are in. As it gets darker, your pupil gets bigger. You need to match whatever you are looking through..wether it be a scope or binos to your pupil. If you take the front number into the back number you will get the exit size. example....10 x 40
10 power goes into 40 four times or 4mm. the higher the number, such as 10 x 50 the better. This would give you 5mm and would be outstanding for light gathering. Beware of 10 x 25 or other smaller numbers as you will not be able to see well in low light conditions. If you look through a 20 to 60 by 80 scope you will see what I am talking about. If you turn the scope to 20 power, you have a 4mm objective going into the 80mm lens and you can see the complete view of the scope. If you jack it up to 60 power, the view is constricted down to between 1 and 2mm. In low light, it is very hard to see. I hope this makes sense. If you got a 20 x 60 x 65 you are only getting 3.3mm exit on the lower power and a little over 1mm on the higher power. Therefore, the 80mm is a better scope for looking through in low light conditions but much heavier to carry. If you want to go with a smaller scope, then you need to sacrifice the lens size to a 15x opposed to the 20x. That would give you a little over 4mm and matches your pupil alot better. Sorry for being so windy.

TC,
While what you are saying is technically correct, the lens coatings will determine how much light gets through. Also, optical quality is a major part. A 65mm Swaro, Leica, or Zeiss will be better than a Bushnell, Nikon, Cabelas, etc., 80mm spotter.

That goes without saying. I agree with you 100%, The glass is the most important feature in any scope or bino. But the objective still needs to match your pupil for optimum low light performance. If a guy can't afford the high end glass, keep this in mind. Another very important feature is the focus adjustment. Try to find a scope that has a forgiving adjustment. Some scopes have a very minimal area that focuses to your eye. Maybe 1/8" or slightly higher. Go to sportsmans warehouse or somewhere that will let you try before you buy and you will be further ahead. Some of the lower end scopes aren't too bad. Nikon is one of those companies that has a great line of scopes. The best binocular buy I have had is a 10 x 50 Nikon Action. The focus is awesome and the clarity is very good for 100 bucks.