August 27th, 2015

Assess Scope Optical Performance Using ScopeCalc.com

ScopeCalc.com

Zeiss DiavariHunters and tactical shooters need scopes with good low-light performance. For a scope to perform well at dawn and dusk, it needs good light transmission, plus a reasonably large exit pupil to make maximum use of your eye’s light processing ability. And generally speaking, the bigger the front objective, the better the low-light performance, other factors being equal. Given these basic principles, how can we quickly evaluate the low-light performance of different makes and models of scopes?

Here’s the answer: ScopeCalc.com offers a FREE web-based Low-Light Performance Calculator that lets you compare the light gain, perceived brightness, and overall low-light performance of various optics. Using this scope comparison tool is pretty easy — just input the magnification, objective diameter, exit pupil size, and light transmission ratio. If the scope’s manufacturer doesn’t publish an exit pupil size, then divide the objective diameter in millimeters by the magnification level. For example a 20-power scope with a 40mm objective should have a 2mm exit pupil. For most premium scopes, light transmission rates are typically 90% or better (averaged across the visible spectrum). However, not many manufacturers publish this data, so you may have to dig a little.

ScopeCalc.com

ScopeCalc.com’s calculator can be used for a single scope, a pair of scopes, or multiple scopes. Once you’ve typed in the needed data, click “Calculate” and the program will produce comparison charts showing Light Gain, Perceived Brightness, and Low-Light Performance. Though the program is easy to use, and quickly generates comparative data, assessing scope brightness, as perceived by the human eye, is not a simple matter. You’ll want to read the annotations that appear below the generated charts. For example, ScopeCalc’s creators explain: “Perceived brightness is calculated as the cube root of the light gain, which is the basis for modern computer color space brightness scaling.”

Permalink Optics, Tech Tip No Comments »
July 21st, 2015

Big Unclaimed Special Order Sale Now at Midsouth

unclaimed special items sale midsouth shooters supply scope dies discount

Here’s a special savings opportunity from Midsouth Shooters Supply — save up to 60% on unclaimed special order items. From time to time, Midsouth’s customers request special order items but never claim them. To clear space for other inventory, Midsouth is running a blow-out sale on these items. If you’re looking for a super deal on dies, rings, and other gear, check out this Unclaimed Special Order Item Sale. Here are just a few examples of items at 30% off normal pricing:

AMMO: 6.5x55mm 100 Grain A-Max 20 Rounds (Closeout $28.90)
SCOPE: Leupold VX-2 4-12x50mm CDS Duplex Reticle Matte Finish (Closeout $374.50)
DIES: Forster 223 WSSM Full Length Die & Ultra Micrometer Seater Set (Closeout $67.92)
SCOPE MOUNT: Integrated 1″ Ring Mount Weatherby/Howa Short Action (Closeout $36.96)
KNIFE: Gerber Powerframe Serrated Knife (Closeout $14.91)

Permalink Hot Deals, Optics No Comments »
June 27th, 2015

Ring Reducers Adapt 30mm Rings to Fit 1″ Scope Tubes

Forum member Jacob spotted this simple, but effective set of scope ring inserts on the Brownells’ Website. With these inserts, you can use a scope with 1″-diameter body in 30mm rings. Non-marring, matte black Delrin sleeves surround the scope tube so it can fit larger-diameter rings. Each sleeve comes in two parts for easy installation around your scope tube. Ring Reducers are sold as front/rear kits. Cost is $14.99 for the 30mm to 1″ ring adapters, item 084-000-091.

Brownells Ring Reducers

Note: These Brownells units simply function as plastic bushings. Unlike Burris Signature Ring inserts, they do not allow you to “pre-load” windage or elevation. If your rings are misaligned, the Brownells Ring Reducers won’t correct that problem.

Permalink Gear Review, Optics No Comments »
June 24th, 2015

Sightron SIII 10-50x60mm Under $980.00 — Sales Help Forum

Sighton 10-50x60 scope optic competition target dot mildot MOA riflescope sale

Need a high-magnification scope for long-range competition? Among quality scopes with 40+ power, we think the Sightron SIII 10-50x60mm scope may be the best value on the market right now. For a limited time, these scopes are available through Amazon.com for under $980.00. That’s less than half the price of a Leupold 7-42x56mm VX-6, and about 42% of the cost of a Nightforce 15-55X competition model. The Sightron is a good product with a lifetime manufacturer’s warranty.

Half the Cost of Leupold 7-42x56mm
Proceeds from Each Sale Help Support Shooter’s Forum

MOA-2 Reticle

Target Dot Reticle

Fine X-Hair Reticle

Mil-Dot Reticle

NOTE: There are a variety of reticle options and both 1/4-MOA and 1/8-MOA click versions are offered. Read the product description carefully when ordering to be sure you’ve selected your preferred reticle type and click value.

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Permalink Hot Deals, Optics 4 Comments »
May 26th, 2015

How to Use Mil-Dot Scope Reticles to Estimate Range

NRA Video Milrad MIL mil-dot range reticle

MIL-system scopes are popular with tactical shooters. One advantage of MIL scopes is that the mil-dot divisions in the reticle can be used to estimate range to a target. If you know the actual size of a target, you can calculate the distance to the target relatively easily with a mil-based ranging reticle. Watch this helpful NRA video to see how this is done:

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Permalink - Videos, Optics 4 Comments »
May 25th, 2015

Dope for Your Scope — Handy Laminated Ballistics Card

JBM laminated ballistics card zak smith

Tactical ace Zak Smith of Thunder Beast Arms employs a simple, handy means to store his elevation and wind dift data — a laminated data card. To make one, first generate a come-up table, using one of the free online ballistics programs such as JBM Ballistics. You can also put the information in an Excel spreadsheet or MS Word table and print it out. You want to keep it pretty small.

Above is a sample of a data card. For each distance, the card includes drop in inches, drop in MOA, drop in mils. It also shows drift for a 10-mph cross wind, expressed three ways–inches, MOA, and mils. Zak explained that “to save space… I printed data every 50 yards. For an actual data-card, I recommend printing data every 20 or 25 yards.” But Zak also advised that you’ll want to customize the card format to keep things simple: “The sample card has multiple sets of data to be more universal. But if you make your own data card, you can reduce the chance of a mistake by keeping it simple. Because I use scopes with MILS, my own card (photo below left) just has three items: range, wind, drop in MILS only.”

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Permalink Gear Review, Tactical No Comments »
May 14th, 2015

How to Check Your Scopes’ True Click Values

Scope Riflescope turret click MOA MIL value

Nightforce scope turretLet’s say you’ve purchased a new scope, and the spec-sheet indicates it is calibrated for quarter-MOA clicks. One MOA is 1.047″ inches at 100 yards, so you figure that’s how far your point of impact (POI) will move with four clicks. Well, unfortunately, you may be wrong. You can’t necessarily rely on what the manufacturer says. Production tolerances being what they are, you should test your scope to determine how much movement it actually delivers with each click of the turret. It may move a quarter-MOA, or maybe a quarter-inch, or maybe something else entirely. (Likewise scopes advertised as having 1/8-MOA clicks may deliver more or less than 1 actual MOA for 8 clicks.)

Reader Lindy explains how to check your clicks: “First, make sure the rifle is not loaded. Take a 40″ or longer carpenter’s ruler, and put a very visible mark (such as the center of an orange Shoot’N’C dot), at 37.7 inches. (On mine, I placed two dots side by side every 5 inches, so I could quickly count the dots.) Mount the ruler vertically (zero at top) exactly 100 yards away, carefully measured.

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Permalink Optics, Tech Tip 1 Comment »
April 26th, 2015

Review of New Nightforce 3-10x42mm SHV Hunting Scope

Nightforce coyote hunting review scope SHV Tim Titus

LongRangeHunting.com recently published a helpful review of the new Nightforce 3-10x42mm SHV scope. If you’re looking for a hunting optic or you are interested in predator hunting, this review is worth a read. Author Tim Titus, an experienced hunting guide from Oregon, tests the little SHV is the field, bagging a coyote in the process.

Tim was impressed with the 3-10 SHV, given it’s price level: “While the SHV performed flawlessly on this hunt, NXS or ATACR owners will notice some subtle differences in form and function when comparing this scope to its more expensive big brothers. The Nightforce SHV won’t replace the 2.5-10X NXS for those who want to turn turrets on a consistent basis or who have the need for specialized or lighted reticles. But … for current Nightforce owners wanting a more affordable alternative … the SHV opens another playing field in what is still a very upscale optic. I’m confident this new scope will find its way onto many big game and predator hunting rifles.”

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Permalink Hunting/Varminting, Optics 2 Comments »
April 9th, 2015

Trijicon Introduces Four New “AccuPower” Scopes

Trijicon rifle scopes accupower illuminated reticle
Click Photo to View Full-Screen Image

Trijicon has introduced a new line of Second Focal Plane scopes with illuminated reticles. Trijicon’s new AccuPower™ riflescope series includes four models. The smallest AccuPower, well-suited for short-range hunting and 3-Gun Games, is the 1-4×24mm. Next up is a general purpose 3-9×40mm. For hunting and sporting use there are a 2.5-10×56mm and a 4-16×50mm with bigger objectives for better low-light performance. All these four models offer either 1/4-MOA or 0.1 Mil clicks. AccuPower scopes feature aluminum scope tubes, multi-coated lenses, and application-specific illuminated reticles. The 3-9x40mm has a 1″-diameter tube while the other models have 30mm tubes.

The AccuPower series incorporates a hybrid black chrome/etch and fill illuminated reticle system available in red or green, with eleven (11) brightness settings. Notably, there is an “off” feature between each brightness setting.

Four reticle choices are offered: MOA reticle, MIL-square reticle, Duplex crosshair, and the popular competition Segmented Circle crosshair with BDC capabilities.

Permalink New Product, Optics 2 Comments »
March 20th, 2015

Horus Video Explains Sources of Zero Shift in Rifle Scopes

YouTube Preview Image

In the above video, a spokesman for Horus Vision explains how and why scopes can experience zero shift. First, just cleaning the gun can cause a small shift in point of impact. Second, when you re-tighten rings and ring bases, this can cause a change in zero. Horus recommends that you use a torque wrench to confirm that you maintain the same torque settings each time. The same goes for action screw tension — tensioning your action screws can shift the point of impact.

Other factors that can cause a change in zero:

Temperature
Dramatic ranges of temperature will change your zero, because the air density affects the velocity of the bullet. With increased temperature, there may be a higher velocity (depending on your powder).

Gun Handling and Body Position
You rifle’s point of impact will be affected by the way you hold the gun. A “hard hold” with firm grip and heavy cheek weld can give you a different POI than if you lightly address the gun. Even when shooting a benchrest gun, the amount of shoulder you put into the rifle can affect where it prints on paper.

Type of Rifle Support — Bench vs. Field
Whenever you change the type of rifle support you use, the point of impact can shift slightly. Moving from a bipod to a pedestal rest can cause a change. Similar, if you switch from a mechanical rest to sandbags, the gun can perform differently. That’s why, before a hunt, you should zero the gun with a set-up similar to what you would actually use in the field — such as a rucksack or shooting sticks.

shooterXbag.com sandbag

Transportation of Firearms
Even if you don’t mishandle your weapon, it is possible that a shift of zero could occur during transport. We’ve seen zero settings change when a tight plastic gun case put a side load on the turrets. And in the field, if the turret knobs are not covered, they can rub against clothing, gear, storage bags, scabbard, etc. If the knobs turn, it will definitely move your reticle slightly and cause your point of impact to be off.

Permalink - Articles, - Videos, Optics 2 Comments »
March 1st, 2015

Offset Scope Mount Helps Shooter with Vision Problem

offset scope base mountForum member Roy Bertalotto did a real nice off-set scope installation on a bolt gun to help a sight-challenged shooter. Roy explains: “A friend of mine shoots left-handed and has lost the sight in his left eye. I built him a scope mount so he can still shoot left-handed, but now use his right eye.” Roy’s fabrication work is impressive and we praise his efforts to help a fellow shooter stay in the game.

Roy bolted a plate to the existing scope rail on the top centerline of the Rem 700 action. This plate extends a few inches to the right. On the outboard end of the plate, Roy fitted a second scope rail, aligned with the bore. Weaver-based rings are then clamped to the outboard (right side) auxiliary rail.

offset scope base mount

offset scope base mount

offset scope base mount

Be Careful of Canting Issues with Offset Scope Installations
We’re pleased to see that Roy developed a solution for a shooter with an optical disability, but we want to stress that this is a specialized installation that can create some problems with point of impact shift if the gun is not maintained perfectly level. With the amount of horizontal offset (between the scope’s optical axis and the bore axis) built into this rig, if the rifle is canted, point of impact can shift rather dramatically. For a southpaw who is willing to adapt his/her shooting style, it may be better, in the long run, to learn to shoot right-handed if his/her right eye is the only good eye. Likewise, if a right-handed shooter can only see well through his left eye, he may benefit from learning how to hold the stock and work the trigger with his left hand. The shooter could still work the bolt with his non-trigger hand. Changing from right-hand to left-hand shooting (or vice-versa) may require a stock swap if the stock is not ambidextrous.

Permalink Gunsmithing 2 Comments »
December 29th, 2014

Understanding Minutes of Angle (MOA) — Intro Video

In this NSSF Video, Ryan Cleckner, a former Sniper Instructor for the 1st Ranger Battalion, defines the term, “Minute of Angle” (MOA) and explains how you can adjust for windage and elevation using 1/4 or 1/8 MOA clicks on your scope. This allows you to sight-in precisely and compensate for bullet drop at various distances.

one minute of angle

For starters, Ryan explains that, when talking about angular degrees, a “minute” is simply 1/60th. So a “Minute of Angle” is simply 1/60th of one degree of a central angle, measured either up and down (for elevation) or side to side (for windage). At 100 yards, 1 MOA equals 1.047″ on the target. This is often rounded to one inch for simplicity. Say, for example, you click up 1 MOA. That is roughly 1 inch at 100 yards, or roughly 4 inches at 400 yards, since the target area measured by 1 MOA increases in linear fashion with the distance.

Story sourced by Edlongrange.
Permalink - Videos, Shooting Skills 4 Comments »
December 14th, 2014

Protect Pricey Optics with Scope-Coats

ScopeCoat Scope ProtectorWith the price of some premium scopes approaching $3000.00 (and beyond), it’s more important than ever to provide extra protection for your expensive optics. ScopeCoat produces covers that shield scopes with a layer of neoprene rubber (wetsuit material) sandwiched between nylon. In addition to its basic covers, sold in a variety of sizes and colors, ScopeCoat has a line of heavy-duty 6mm products that provide added security.

scopecoat scope optics protector cover neoprene padded

Triple-Thickness XP-6 Model for Added Protection
The XP-6 Flak Jacket™ is specifically designed for extra protection and special applications. The 6mm-thick layer of neoprene is three times thicker than the standard ScopeCoat. XP-6 Flak Jackets are designed for tall turrets, with sizes that accommodate either two or three adjustment knobs (for both side-focus and front-focus parallax models). To shield an expensive NightForce, March, or Schmidt & Bender scope, this a good choice. XP-6 covers come in black color only, and are available for both rifle-scopes and spotting scopes.

ScopeCoat Scope ProtectorThe heavily padded XP-6 Flak Jacket is also offered in a Zippered version, shown at right. This is designed for removable optics that need protection when in storage. The full-length, zippered closure goes on quick-and-easy and provides more complete protection against dust, shock, and moisture. MSRP is $30.00.

Special Covers for Binos and Red-Dots
ScopeCoat offers many specialized products, including oversize covers for spotting scopes, protective “Bino-Bibs” for binoculars, rangefinder covers, even sleeves for small pistol scopes and red-dot optics. There are also custom-designed covers for the popular Eotech and Trijicon tactical optics. Watch the Shooting USA video below to see some of ScopeCoat’s latest specialty covers.

Permalink Optics 2 Comments »
November 2nd, 2014

How to Zero Your Hunting Rifle the Easy Way

We are in the thick of hunting season. If you need to re-zero your favorite deer rifle, here is a dead-simple way to zero your rifle in two or three shots. The method is based on the principle of moving your cross-hairs to the point-of-impact (POI) of your first shot. You’ll need a good set of rests that will hold the gun steady while you (or a buddy) clicks the scope.

After bore-sighting, fire one round at the center of the target. Then place the rifle so the center of the cross-hairs is exactly on your original point of aim. Next, without disturbing the gun in any way, dial your turrets so that the center of the cross-hairs moves over the center of your group. That’s it. You’re now zeroed. Having a helper steady the gun as you click the turrets will make this “no-math” method work more effectively.

Click-to-Initial POI Zeroing Method Demonstrated

Simple Sight-In Procedure
scope zeroing procedurePut the center of your cross-hairs on the target and take one shot. Then reposition the rifle in your bags so the center of the reticle is back on the center of the target. Make sure the rifle is secure in this position (have a friend hold the rifle if necessary). Now, using your elevation and windage knobs (while looking through the scope), simply click the center of the cross-hairs to the middle of the bullet hole — without moving the rifle. You are moving the center of the reticle on to the bullet hole. Take a second shot. The second bullet hole should now be in the center of the target. Repeat the process if needed with a third shot. This procedure works at any distance.

Permalink Hunting/Varminting 3 Comments »
September 6th, 2014

NSSF Video Provides Helpful Scope Mounting Advice

Rifle scope mountingThe National Shooting Sports Foundation (NSSF) has created a video with helpful tips on mounting scopes, and adjusting the position of scopes to suit the shooter. This video, hosted by Ryan Cleckner, a former U.S. Army Sniper instructor, is aimed primarily at “hard-holders” who shoot prone. The video should prove useful for tactical shooters, varmint hunters, and F-Class shooters. Ryan does explain that, if you plan to use your rifle in standing, sitting, and prone positions, you need to set the scope in a “happy medium” position that provides sufficient eye relief in all shooting positions.

Ryan has an interesting method for leveling a rail-mounted, flat-bottomed scope (i.e. one with a flat surface under the turret housing). He simply inserts a small metal bar between rail and scope, and aligns the straight edges along the bottom of the scope turret housing with the flats on the rail (see photo). Watch how he does this on the video — it’s pretty clever. One other highlight of the video is the segment where Ryan shows how to adjust the ocular on his Leupold scope to provide the best (sharpest) image of the reticle. Ocular/reticle adjustment is covered in minutes 11:00-13:00 of the video.

YouTube Preview Image

The video has some faults. Some of the advice, such as “always mount the scope as low as possible” is counter-productive for benchrest shooters who want to keep their heads OFF the stock. In addition, Ryan does not explain that, with a variable power scope, proper eye relief may change considerably with the level of magnification. If you have an 8-32X scope, for example, you can set everything up perfectly for 8X magnification, only to find that you need a LOT more eye relief at 32X. We recommend positioning the scope so it provides sufficient eye relief at the highest magnification you regularly use.

Permalink Optics, Tech Tip 5 Comments »
September 5th, 2014

Steiner Offers 10% Off GS3 Scopes and Predator Binoculars

Need a hunting scope or a good pair of compact binoculars? With Steiner’s Big Game Fall Optics Promotion, you can get 10% off retail price through the end of September on Steiner GS3 Riflescopes and Predator Binoculars. The savings are automatic — there are no rebate forms, no waiting — just instant savings. And the GS3 scopes are very nice. We’ve tried them in the field. They are sharp and clear, with nice controls. The 5X magnification range is definitely a plus for hunters.

Hunters Will Enjoy This Video. It’s Definitely Worth Watching for the Outdoor Photography.

GS3 Riflescopes
2-10×42(Item No. 5004)
3-15×50 (Item No. 5005)
3-15×56 (Item No. 5006)
4-20×50 (Item No. 5007)
4-20×50 (Item No. 5008)
Predator Binoculars
8×22 (Item No. 2441)
10×26 (Item No. 2442)
8×42 (Item No. 2443)
10×42 (Item No. 2444)

The new Steiner GS3 scopes utilize exclusive CAT (color adjusted transmission) lens coatings to amplify contrast in the peak human vision sensitivity range. The optimized contrast helps separate game from leafy or shadow-dappled backgrounds. The GS3’s 5x zoom range gives hunters great flexibility. Zoom to low magnification for a wider field of view, then zoom in at five times higher power when you spot your prey. The GS3 series scopes provide excellent low light performance, and mount on most rifles with standard-height rings.

Steiner GS3 rifle scope fall hunting optics sale promotion

Steiner Predator Binoculars also utilize the game-revealing CAT lens coating to help hunters detect game in heavy cover and leafy environments. They feature a roof prism design in a tough Makrolon® housing. The high definition lenses deliver very good low light performance. At approximately 10 ounces in weight, the 8×22 and 10×26 compact models are small enough to fit in a pocket. The larger 8×42 and 10×42 models (below) offer greater low-light performance. We wish these binocs had captive lens covers, however. We try to keep ocular and objective lenses always covered except when glassing.

Steiner GS3 rifle scope fall hunting optics sale promotion

Permalink Hot Deals, Optics No Comments »
August 1st, 2014

Leica Offers $200.00 Trade-In Value for Any Functioning Scope

leica scope trade-in logo offerHave you got an old “Leapers” scope or other not-so-great optic that you’re embarrassed to mount on a rifle? Well now you can turn that ugly old optic into real money — two hundred dollars to be precise. Leica just announced a trade-in offer that provides a serious incentive to unload an old scope you don’t want or use. No broken scopes please — to qualify as a trade-in, the old scope much be functional with no broken parts. Here’s how the trade-in program works…

When you purchase a new Leica ER i riflescope from any authorized North American Leica dealer, you can receive $200.00 cash back by simply trading in a functioning riflescope of any make or model. Purchase your scope and send your trade-in to Leica between August 1 and October 31, 2014, to receive $200 by mail. The Leica ER i comes in two models: 2.5-10x42mm and 3-12x50mm. Both are available in three reticle configurations: Classic L4-A, Ballistic, and IBS.

To qualify to receive the $200 cash back, you must fill out Leica’s Trade-in Form and mail it to Leica along with your functioning trade-in scope. You must also include:

1. Copy of the sales receipt for the new Leica ER i scope.
2. Completed original ER i warranty registration

leica er i scope trade in promotion

There is no brand or price limit on the trade-in. Leica will accept any brand, make or model of trade-in scope, so long as it is “functional” and a clear image and reticle are visible through the scope.

In fact, you might even find a new scope for less than twenty bucks. We found a Tasco 4x15mm scope on sale at MidwayUSA for just $9.99. And — get this — Midway is even offering free shipping on this item with orders of $25.00 or more. So if you and your buddies buy a total of three scopes (as one order) you can get them all delivered for free! CLICK HERE for $9.99 Tasco.

tasco midwayusa 9.99 scope

With this Tasco, you can shell out whopping $9.99 for a qualifying trade-in scope, and save $200.00 on a life-time guaranteed Leica. That’s smart shopping.

Permalink Hot Deals No Comments »
July 31st, 2014

Big Rebates on Burris Optics, Including Eliminator Laser-Scopes

Burris rebatesBurris Optics is currently offering significant rebates on three lines of scopes. You can get up to $100.00 in rebates on Burris Tactical and Fullfield II scopes. For the innovative Eliminator optics with built-in laser rangefinders, the savings are even bigger — you can get up to $200.00 in rebates with your purchase. We like the Eliminator scopes for Varmint hunting. The built-in rangefinder instantly calculates the needed hold-over, based on the target distance. Then the scope displays the corrected aim point as a red dot on the vertical cross-hair. Just put the red dot on your target and pull the trigger. The Eliminator does all the work for you — no turret clicking needed.

CLICK HERE for Burris REBATE Details and Forms

Burris rebates

Rebate Instructions
These Burris products are available now at Grafs.com. Rebates available for purchases made between July 1, 2014 and December 31, 2014. Mail-in form must be signed, dated, and post-marked by January 31, 2015. View Full Offer Details.

Burris rebates

Permalink Hot Deals, Optics 5 Comments »
June 29th, 2014

Big Discounts on Nikon AR Riflescopes — Up to $100.00 Off

If you need a scope for your AR-platform rifle, Nikon has you covered. With Nikon’s latest AR New Rules promotion, you can save up to $100.00 on caliber-specific AR riflescopes and mounts.

nikon scope discount sale rebate

The New Rules for AR promotion offers shooters up to $100 instant savings on a wide selection of AR-dedicated riflescopes. The New Rules for AR promotion includes nearly 20 models of AR-dedicated riflescopes, including the M-308, M-223, and P-300 BLK lines. This Nikon promotion is in effect right now, and will run through August 2, 2014. To learn more about the New Rules for AR promotion, visit www.nikonpromo.com.

Permalink Hot Deals, Optics No Comments »
June 26th, 2014

Optics Terminology — Lessons from Swarovski Optik

Swarovski Optik exit pupil scope accurateshooter.comWhen shopping for a new riflescope or spotting scope it’s easy to get confused by all the technical terminology. Do you wish you had a better way to compare scopes — beyond just size, weight, and price? Well Swarovski Optik can help. The Swarovski Hunting Blog offers a helpful guide to technical terms used when comparing scope specifications. Here are some important definitions, expressed in layman’s language:

Objective Lens Diameter
The objective lens diameter determines the size of the optical system’s entrance pupil. The bigger the objective lens diameter, the more light the system can capture. However, the size of the objective lens does not determine the size of the field of view.

Exit Pupil
The size of the Exit Pupil is determined by the objective lens diameter and the magnification. If you look at the eyepiece from a distance of around 30 cm (11.8 in), the Exit Pupil appears as a bright disc.

For calculating the Exit Pupil the formula is:

Exit Pupil = objective lens diameter ÷ magnification (expressed in power number).

The larger the Exit Pupil, the more light will reach the eye.

Swarovski Optik exit pupil scope accurateshooter.com

Field of View
The Field of View is the size of the circular section of the area which can be observed when you look through a long-range optical device. In the case of rifle scopes, it is specified at a distance of 100 meters or 100 yards. For example, 42.5 m at 100 m or 127.5″ at 100 yards. As an alternative, the Field of View can also be stated in degrees (e.g. 6.6°).

NOTE: The technically-feasible size for the Field of View is essentially determined by the magnification. The higher the magnification the smaller the Field of View.

Swarovski Optik exit pupil scope accurateshooter.com

Twilight Factor
The Twilight Factor defines the optical system’s performance in poor light. The statement “the greater the twilight factor, the better the suitability for twilight” only applies if the exit pupil is larger than or at least as big as the eye’s pupil. The pupil in the human eye can only open to around 8 mm. As we get older, our eyes become less flexible, which limits our ability to see things in twilight or at night. Therefore [an optic’s] exit pupil cannot always be fully utilized.

For calculating the Twilight Factor the formula is:

Twilight Factor = root of ( magnification x objective lens diameter ).

NOTE: Spotting scopes have extremely high twilight factors because of their high magnification and large objective lens diameter. But [when used at high magnification] their small exit pupil can make them [somewhat difficult] to use in twilight.

CLICK HERE to Read Full Article (with more illustrations).

Photos copyright Swarovski Optik Blog, all rights reserved.

Story Tip by EdLongrange. We welcome reader submissions.
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