Here Is What A Basic Of Monocular Beginner Must Understand

Numbering And Symbol In Monocular Means

1. Most Beginner Will Be Wondering What Is 8x21 Or 10x50 Means. Generally Most Beginner Will Calculate Power By Just Simply Multiple It (i.e. 8x21 : 168x Power, 10x50 : 500x Power) But This Is Grossly Wrong. 
2. Here Is What Those Value Means

• 8x21 : 8 Magnification, 21mm Objective. 10x50 : 10x Magnification, 50mm Objective
• 6.0° FOV Is Field Of View In Degree. A Bigger Number Means A Wider Area Of Coverage When Viewing Thru A Monocular
• Linear FOV (i.e. 131m @ 1000m) Means A Linear Area Of 131m Width Can Be Seen Using This Binocular When Object Is At 1000m Away. A Higher Number Indicated A Wider Are Coverage When Viewing Thru A Monocular

3. Other Important Things To Know About Monocular

• Coatings : Coatings Is An Anti Reflective Layer On Surface Glass That Enhances The Light Transmission Of A Glass. A Uncoated Glass Reflect 4% Light Per Surface (8% Light Loss In Normal Glass Due To Reflection, 2 Surface)
• The Best Coating Is Fully Multi-Coated (Each And Every Layer Of Air-Glass Surface Is Coated With Multiple Layer Of Anti-Reflective Coatings) Some Monocular Might Have Only Fully-Coated Optics (At Least A Coating Layer On Each Surface Of Glass) Or Multi-Coated (At Least A Multiple Layer Of Coatings On At Least 1 Surface Of Glass)
• Bak4 Prism And Bak7 Prism : BaK Stands For Barium-Krown (BaK) Which Is The Reflective Index Of A Prism. A Higher Index Will Have A Smaller Critical Angle And Provide Full Internal Reflection. This Is Only Important To Ensure A Full Circle Of Illumination To Reduce Vignetting Effect. BaK7 Can Allow Full Illuminated Circle Up To About 48-50mm Depends On The Prism Size
• Eye Relief : Eye Relief Is The Most Comfortable Distance Between The Eye And Also The Eyepiece Lens Of A Monocular To Provide A Fully Illuminated Field Of View Without Vignetting Or Black-Out. Those Who Are Using Eye Wear Benefit From Long Eye Relief As There Is No Need To Remove The Glasses When Using A Long Eye Relief Monocular
• Pupil Exit : A Pupil Exit Is The Width Of The Light Output. The Larger The Pupil Exit, The Brighter Is The Objects Appears. The Maximum Effective Pupil Exit Will Be Around 7mm. A Smaller Pupil Object Translate To Dimmer View. Pupil Exit : Objective Diameter/Magnification

Popular Misconception Or False Rate Monocular By Manufacturer

1. Optical Rating : i.e.60x90, 30x60 etc. These Will Confuse Consumer As Inaccurate Rating Does Not Provide The Real Performance Of Monocular, In Fact This Only Translate To A Poor Or Low Quality Design. Why Are These Rating Falsely Rate And Unlikely To Be Real? Imaging The 90mm - Translate To 90mm Of The Monocular Objective. Does The Monocular Appears To Have A 90mm Objective. This Kind Of Monocular Will look More Like A Telescope Instead. 
2. Magnification : All Branded Or Expansive Monocular Have Only Rating Of 8x42, 9x32 etc. There Is No Leica Or Zeiss Being Rated 60x90 or more. A Real 60x90 Rated Monocular, Image Will Be Extremely Dim Plus Impossible To Handheld. Higher Magnification Translate To Need For More Stability. 7X Monocular, If Have Shake Or Movement Of 1mm, Will Have Image Moving Up And Down 3m Difference At 300m. A 60x Monocular With Movement Of 1mm Translate To 6m Meter Movement @ 100m Distance. A Car Height Is About 1.5m. Logical Sense It Is Not Possible To Hand Held A High Power Monocular. Most Expert Agree That Maximum Of 10x Is Upper Limit For Handheld, Anything More Will Be Too Unstable Handheld
3. Prism Type. Many Manufacuter Claims A BaK4 Is Better Than A BaK7 Prism. Many Unbranded Binocular Are Actually Built With Chinese BK4, Not BaK4. BK4 Has A Lower Refractive Index Than Real BaK4 And Has More Impurity, Leading To Image Softness. A Real Bak4 Prism Binocular Typically Cost More Due To High Manufacturing Cost Of BaK4 (Real BaK4 Is Manufactured By Schott AG, Germany). High Quality BaK7 Monocular Will Perform Better Than A Low Quality BK4 Monocular