Thread: Light gathering and twight factor

" you really need to go out in twilight and play with your variable scope to find out what power works for you. "

I guess there are two situations:

You are about to buy a new scope and want to work out how big you need the objective. All I can say is that bigger is better and 21st century is better than 20th. Go by reputation and practicality: do you want to carry a 50 or 56mm scope ? Can you mount it on your gun and will you need a raised cheekpiece ? My 2c is that I've seen a noticeable difference between 44, 50 and 56 mm in the 3-12 range. 50 and 56 are brighter than I can see with my naked eye so they are bright enough. It's not often you want to shoot something you can't see without optics. Of course if you can see it by eye but not through your scope you're onto a loser and that has happened to me often with a 2-7x32. Note that binoculars have twice the glass (sounds obvious) so my 8x32 binos are pretty much the same as my 3-12x50 scope and both are brighter than naked eye which is bright enough.

Then there is when you've got a scope and want to know quickly what power to turn it to for best visibility when shooting. As said, go out in the bush at a long distance and watch as the light fades, turning the power up and down for comparison. Look at something: "is it a log or is it a deer ?" Try something bright and something dark like a log inside the bush edge. If you've got a better optic to compare with, use that too. You will need to rest your gun solidly so there is no tremor. With my 3-12x50, I found I could see best at about 7x (later on I calculated out why ...) but it was true, taking into account size of image and brightness I could see the most detail at 7x. Other factors can affect your choice; in my case I've got a first focal plane unilluminated reticle which is pretty fine and hard to see below 4x and a lot easier to work with over 10x. If you have illumination, then flare may obscure the target at some powers, specially depending on the condition of your eyes. I you're spotlighting you will need wide field of view and for possums a low power helps to focus if they are very close. Some scopes have poor resolution in their upper range and whether its bright or big or not you can see better at lower power.