Most IF binoculars are 7x magnification and have a large depth of focus which usually eliminates the need for focusing adjustment at distances over 50m. ![]() ![]() Centre focus CF, is more popular than individual eyepiece focusing IF especially when you need to focus at different distances under 50m. This can be done by entering the equation into an Excel™ spreadsheet, and producing a table like the one shown below a pre-made spreadsheet can be downloaded (in English) here. GA rubber armouring and W or WA wide angle. Therefore, it is advisable to calculate ranges prior to going on effort. Range estimation needs to happen quickly in the field, especially with regards to exclusion zones. Use the following equation to estimate range: Then calculate the number of mils, for example if a marine mammal is sighted at 10 reticles, and each reticle is 5 mils, it would be 50 mils. When a sighting occurs, align the top reticle with the horizon, and count down to the animal. Number of mils in each reticle of your binoculars (refer to your binocular specifications).Īdd together your eye height and the height of the observation platform to find your height above sea level.Range can be estimated using different methods, but described here is how to estimate range using reticle binoculars. Estimating range to marine mammals is a key skill for Marine Mammal Observers.
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