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 30th, 2014

New Lyman BoreScope with Digital Screen and Output to Laptops

Every rifle shooter should have access to a borescope. These devices reveal the condition of the inside of your barrel. Do you have a carbon ring problem? Is there jacket fouling near the muzzle? Are the edges of your lands worn away? All these common conditions can be revealed by a quality borescope.

UPDATE: MSRP will be under $300.00 and the unit should be available in March. Lyman told us: “We expect to have these available in March 2015. The price is expected to be $299.95. We will have this available for pre-order via our website in early 2015.”

And now new digital/optical technology makes the borescope easier than ever to use. For 2015, Lyman will introduce a new, affordable borescope that employs digital imaging (with a micro-camera). You no longer have to peer into an old-fashioned eyepiece. With the new Lyman borescope you can view the inside of your barrel via a small portable display screen. That’s handy. In addition, the borescope images can be displayed on your laptop or mobile device. Lyman provides a USB cable and software that allows you to view the borescope’s image output on your computer (plus you can record images for future reference). The unit fits bores .20 caliber and larger.

borescope digital lens viewscreen USB ipad computer camera micro-camera

Sorry, we don’t have an exact price yet, but we’ve been told that this new product will be less expensive than current, conventional precision borescopes with glass-lens eyepieces. Here’s what Lyman says about it’s new product:

Lyman’s new Borescope provides active shooters with the means to carefully inspect the bores of their firearms for wear, throat erosion, tool marks, and other rifling or chamber damage, as well as for checking for fouling. The scope will fit 20 caliber and larger barrels and works with miniature camera technology. The display will show a clear image of the inside of the barrel and also allows you to take a photo of the bore. The image will storage on a standard SD card and can later be viewed on a computer or lap top. A separate cable (with USB connection) and CD are also available so that the Borescope rod can be connected directly to your computer or lap top. If you prefer to view only on your computer or lap-top, the Borescope rod is available separately (without the display unit) and plugs into the computer with a USB connection.

New product tip from EdLongrange. We welcome reader submissions.
Permalink New Product, Optics 3 Comments »
November 30th, 2014

PrecisionRifleBlog.com Tests Range-Finding Binoculars

Last year, PrecisionRifleBlog.com published results from the most comprehensive field test of rangefinder binoculars ever conducted. The comparison test included virtually every product then available in the USA. If you are thinking about getting a set of binoculars with range-finding capability, you should definitely read this test. Here we summarize key findings of the test, but you’ll want to read the FULL STORY.

Six range-finding binocular optics (and two monocular rangefinders) were field-tested in a variety scenarios to see which had the best performance in terms of both optical clarity and ranging capabilities. The results are based on over 10,000 data points collected from the field over 3 months of testing. Cal Zant, author of PrecisionRifleBlog.com, published a series of posts with exhaustive details about his optical and ranging tests and results, but we’ll hit the highlights here.

Ranging Binocular Field Test and Reviews

VOICE FILE: Click Button to Hear Cal Zant TALK about Rangefinder Binocular Test

Six of the models tested were binoculars, and the other two were monoculars. The Leupold monocular was included for reference, because many shooters have a 1,000-yard rangefinder similar to the RX-1000. The Vectronix Terrapin model was included as the control for ranging performance, because it is known to be an extremely accurate rangefinder (spoiler alert: it is). Cal provides a very detailed side-by-side spec comparison for these models in one of his posts.

Ranging Test Results

Rangefinder Binocular ReviewEach model was used to range 500+ times in a variety of scenarios from 25 to over 30,000 yards. The tests showed these models had similar performance at close and mid-range targets, but at 600 yards their performance started to diverge … so that is where most of the testing was focused.

The chart below summarizes the ranging performance found on the test targets in ideal conditions, which was from a sturdy tripod, at sunset, with 10+ mile visibility. The exact target shape and surroundings varied, but the targets were all approximately 2 MOA wide, highly reflective, and perpendicular to the rangefinder. Specifics on target dimensions, view from the ranging position, and target surroundings are given in the detailed ranging performance results post.

Rangefinder Binoculars Review Ranging Performance Under Ideal Light Conditions

Vectronix is the leader of the rangefinder world, and that was proved once again in these tests. The new Leica Geovid HD-B wasn’t far behind them, with accurate ranging beyond 1 mile. The Zeiss Victory RF also had surgical precision off a tripod, although it had a reduced range compared to the Vectronix and Leica. The Bushnell Fusion 1 Mile also proved to be able to range targets out to their claimed max range of 1,760 yards.

PrecisionRifleBlog.com also tested the ranging performance of each model in bright lighting conditions, and offhand as well. The data from those tests also contained a few surprises. To determine how accurate each model really was, Cal Zant carefully analyzed the results from each model when aimed at precisely positioned, “known distance” targets. To see how those tests turned out, or learn more details about specific models, GO TO full results.

Optical Test Results

Rangefinder Binoculars Review Optical QualityFor the optics tests, Cal’s goal was to find an objective, data-driven approach to testing optical performance. What he came up with was placing eye exam charts from 600 to 1,400 yards with different size letters, and then recording what two different people could accurately read with each model. The data for each unit was summed into a single score so they could be ranked relative to how much detail the testers could make out. More specifics are provided regarding how the test was conducted and how scores were calculated in the optical performance results post. Here are the results from Cal’s data-driven approach:

Rangefinder Binoculars Review Optical Quality

The Leica Geovid HD-B edged out the other models for the top spot, with its completely new, Perger-Porro prism design. The original Leica Geovid HD, and Zeiss Victory RF also showed great optical clarity.

The Rest of the Story

Cal’s full series of posts is very informative. He’s done tons of analysis on the data, and summarizes it in several charts that provide a lot of insight. Cal is also in the process of publishing detailed reviews on each model, including notes he and the other testers compiled for each unit. They used them all — a lot, so they have a unique perspective on what’s good or bad about each. Find out more at the link below:

CLICK HERE to Read Full Article with More Info

Permalink Hunting/Varminting, Optics 4 Comments »
October 7th, 2014

MIL vs. MOA Reticles — Which Are Better for Tactical Tasks?

MIL or MOA — which angular measuring system is better for target ranging (and hold-offs)? In a recent article on his PrecisionRifleBlog.com website, Cal Zant tackles that question. Analyzing the pros and cons of each, Zant concludes that both systems work well, provided you have compatible click values on your scope. Zant does note that a 1/4 MOA division is “slightly more precise” than 1/10th mil, but that’s really not a big deal: “Technically, 1/4 MOA clicks provide a little finer adjustments than 1/10 MIL. This difference is very slight… it only equates to 0.1″ difference in adjustments at 100 yards or 1″ at 1,000 yards[.]” Zant adds that, in practical terms, both 1/4-MOA clicks and 1/10th-MIL clicks work well in the field: “Most shooters agree that 1/4 MOA or 1/10 MIL are both right around that sweet spot.”

Mil MOA reticle ranging PRS tactical minute angle precision rifle series

READ MIL vs. MOA Cal Zant Article.

Zant does note that a whopping 94% of shooters in the Precision Rifle Series (PRS) used a mil-based reticle. However, Zant says: “This does NOT mean MIL is better. It just means MIL-based scopes are more popular.” Zant agrees with Bryan Litz’s take on the subject: “You can’t really go wrong with either (MIL or MOA). They’re both equally effective, it comes down to how well you know the system. If you’re comfortable with MOA, I wouldn’t recommend switching to MIL. I have a few MIL scopes but primarily because they’re on rifles used for military evaluation projects, and that community is now mostly converted to MILS, so when in Rome….”

We recommend you read Zant’s complete article which is very thorough and is illustrated with helpful graphics. Here are the key points Zant makes in his MIL vs. MOA analysis:

MIL vs. MOA — Key Points
There are a handful of minor differences/trade-offs between MIL & MOA, but there are no inherent advantage to either system. Most people blow the small differences WAY out of proportion….Here are the biggest differences and things to keep in mind:

  • Whatever you decide, go with matching turret/reticle (i.e. MIL/MIL or MOA/MOA)
  • 1/4 MOA adjustments are slightly more precise than 1/10 MIL.
  • MIL values are slightly easier to communicate.
  • If you think in yards/inches the math for range estimation is easier with MOA. If you think in meters/cm the math is easier with MIL.
  • When your shooting partners are using one system, there can be some advantage to having the same system.
  • Around 90% of the PRS competitors use MIL.
  • There are more product options (with ranging reticles) in MIL.

Range Card Print-Outs
Zant makes an interesting practical point regarding range card print-outs. He suggests the MIL System may be easier to read: “You can see in the range card examples below, 1/4 MOA adjustments take up more room and are a little harder to read than 1/10 MIL adjustments.”

mil vs moa reticle scope

Permalink Optics, Tactical 11 Comments »
September 16th, 2014

Get a Free SureFire Flashlight with Leica Rangefinder

Here’s a nice combo offer if you’re thinking about buying a laser rangefinder for the fall hunting season. Right now, if you purchase a Leica CRF 1000-R or 1600-B Laser Rangefinder you can receive a Surefire G2x-Pro flashlight worth $85.00. The rugged, dual-power G2x-Pro should last a lifetime.

This is a limited-time offer works. When you purchase a new Leica CRF Rangemaster 1000-R or 1600-B Compact Laser Rangefinder from any authorized North America Leica Dealer you can receive a Surefire G2X-Pro flashlight and lanyard ($85 value). Send in your mail-in Rebate Form, plus your CRF proof of purchase, to Leica between Sept. 15 and Dec. 31, 2014, to receive your Surefire G2X-Pro flashlight.

Leica Surefire rangefinder laser flashlight rebate promotion

Leica’s CRF 1000-R Rangemaster is an easy-to-use laser rangefinder than can fit in your pocket. The wide field of view makes target identification fast and easy. The CRF 1000-R features built-in angle correction. This provides automatic point-of-aim correction for uphill or downhill shots. That’s a very valuable feature for hunters.

Leica’s CRF 1600-B Compact Laser Rangefinder boasts an integrated precision ABC (Advanced Ballistic Compensation) system. This instantly measures distance, incline, temperature, and air pressure and then calculates hold-over based on selected bullet BC. The 1600-B’s LED display has ambient-light-controlled brightness — a nice feature when you’re in the field. For more info, visit LeicaSportOptics.com

Permalink Hot Deals, Optics No 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 3rd, 2014

Save $50.00 on Leupold VX-2 Scopes with Rebate

It’s “rebate season” for rifle scopes. Leica recently announced a $200.00 trade-in rebate offer, and now Leupold is joining in on the fun with a $50.00 rebate on VX-2 scopes.

Here’s how you can save fifty bucks on a Leupold VX-2.

From August 1 to September 1, 2014, hunters and shooters can receive a $50 rebate on the purchase of select Leupold® VX®-2 riflescopes. To receive the rebate, submit a rebate form with a valid receipt and the original UPC bar code cut from the product packaging. Forms can be obtained at Point of Purchase. The VX-2 rebate forms must be postmarked no later than October 1, 2014.

Alternatively, you can fill out Leupold’s Online Rebate Form. After filling in your personal info, then upload a photo of the sales receipt, plus a photo (or scan) of the product UPC code. If you have a smart-phone, that should be easy, and you don’t even need a stamp or envelope.

Leupold VX2 VX-2 Rebate

Permalink Hot Deals, Optics 1 Comment »
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 No Comments »
July 2nd, 2014

One Dollar Do-It-Yourself Mirage Shield

make your own mirage shield for rifleWant to shoot better scores at your next match? Here’s a smart, inexpensive do-it-yourself project from the good folks at Criterion Barrels. For less than one dollar in materials, in just a few minutes you can create a handy, effective mirage shield, custom-fitted to your favorite rifle.

All precision shooters should be familiar with mirage, a form of optical distortion caused primarily by variations in air temperature. Savvy shooters will use mirage as a valuable tool when gauging wind speed and direction. Natural mirage is unavoidable, but there are many techniques designed to limit its influence in long-range marksmanship.

make your own mirage shield for rifle

A form of mirage can be produced by the barrel itself. Heat rising from the barrel may distort sight picture through your optics, leading to erratic results. Mirage caused by barrel heat can be reduced dramatically by a simple, light-weight mirage shield.

How to Make a Mirage Shield

A mirage shield is an extremely cost-effective way to eliminate a commonly-encountered problem. Making your own mirage shield is easy. Using old venetian blind strips and common household materials and tools, you can construct your own mirage shield for under one dollar.

Materials Required:
1. Vertical PVC Venetian blind panel
2. Three 1”x1” pieces adhesive-backed Velcro
3. Ruler or tape measure
4. Scissors or box cutter
5. Pencil or marker

1. Measure the distance from the end of the receiver or rail to the crown of the barrel.

make your own mirage shield for rifle

2. Using a pencil and ruler, measure the same distance and mark an even line across the blind.

make your own mirage shield for rifle

3. Cut across the line using scissors or a box cutter, shortening the blind to the required length. (Remember, measure twice, cut once!)

4. Expose the adhesive backing on the loop side of the Velcro. Center and apply the Velcro strips on the barrel at regular intervals.

make your own mirage shield for rifle

5. Expose the adhesive backing of the fuzzy side of the Velcro.

6. Place the blind on the upper side of the barrel. Apply downward pressure. Once the Velcro has secured itself to the barrel, separate the two sides. Proceed to mold both sides of the Velcro to fit the contour of their respective surfaces.

7. Reaffix the blind. Barrel related mirage is now a thing of the past!

make your own mirage shield for rifle

How to Remove and Re-Attach the Mirage Shield
Removal of your mirage shield is accomplished by simply removing the blind. You can un-install the Velcro by pulling off the strips and then gently removing any adhesive residue left behind using an appropriate solvent. (Simple cooking oil may do the job.) Caution: With fine, high-polish blued barrels, test any solvent on a non-visible section of the barrel. Before storing the gun, re-oil the barrel to remove active solvents and residual fingerprints.

Permalink Tech Tip 2 Comments »
June 29th, 2014

When Good Scopes Go Bad — Making the Difficult Diagnosis

Riflescopes are mechanical contraptions. One of the sad realities about precision shooting is that, sooner or later, you will experience a scope failure. If you’re lucky it won’t happen in the middle of a National-level competition. And hopefully the failure will be dramatic and unmistakable so you won’t spend months trying to isolate the issue. Unfortunately, scope problems can be erratic or hard to diagnose. You may find yourself with unexplained flyers or a slight degradation of accuracy and you won’t know how to diagnose the problem. And when a 1/8th-MOA-click scope starts failing, it may be hard to recognize the fault immediately, because the POI change may be slight.

When An Expensive Scope Goes Bad
Recently, this editor had a major-brand 8-25x50mm scope go bad. How did I know I had a problem? Well the first sign was a wild “drop-down” flyer at a 600-yard match. After shooting a two-target relay, I took a look at my targets. My first 5-shot group had five shots, fairly well centered, in about 2.2″. Pretty good. Everything was operating fine. Then I looked at the second target. My eye was drawn to four shots, all centered in the 10 Ring, measuring about 2.4″. But then I saw the fifth shot. It was a good 18″ low, straight down from the X. And I really mean straight down — if you drew a plumb line down from the center of the X, it would pass almost through the fifth shot.

That was disconcerting, but since I had never had any trouble with this scope before, I assumed it was a load problem (too little powder?), or simple driver error (maybe I flinched or yanked the trigger?). Accordingly, I didn’t do anything about the scope, figuring the problem was me or the load.

Riflescope Repairs

But, at the next range session, things went downhill fast. In three shots, I did manage to get on steel at 600, with my normal come-up for that distance. Everything seemed fine. So then I switched to paper. We had a buddy in the pits with a walkie-talkie and he radioed that he couldn’t see any bullet holes in the paper after five shots. My spotter said he thought the bullets were impacting in the dirt, just below the paper. OK, I thought, we’ll add 3 MOA up (12 clicks), and that should raise POI 18″ and I should be on paper, near center. That didn’t work — now the bullets were impacting in the berm ABOVE the target frame. The POI had changed over 48″ (8 MOA). (And no I didn’t click too far — I clicked slowly, counting each click out loud as I adjusted the elevation.) OK, to compensate now I took off 8 clicks which should be 2 MOA or 12″. No joy. The POI dropped about 24″ (4 MOA) and the POI also moved moved 18″ right, to the edge of the target.

Riflescope RepairsFor the next 20 shots, we kept “chasing center” trying to get the gun zeroed at 600 yards. We never did. After burning a lot of ammo, we gave up. Before stowing the gun for the trip home, I dialed back to my 100-yard zero, which is my normal practice (it’s 47 clicks down from 600-yard zero). I immediately noticed that the “feel” of the elevation knob didn’t seem right. Even though I was pretty much in the center of my elevation (I have a +20 MOA scope mount), the clicks felt really tight — as they do when you’re at the very limit of travel. There was a lot of resistance in the clicks and they didn’t seem to move the right amount. And it seemed that I’d have four or five clicks that were “bunched up” with a lot of resistance, and then the next click would have almost no resistance and seem to jump. It’s hard to describe, but it was like winding a spring that erratically moved from tight to very loose.

At this point I announced to my shooting buddies: “I think the scope has taken a dump.” I let one buddy work the elevation knob a bit. “That feels weird,” he said: “the clicks aren’t consistent… first it doesn’t want to move, then the clicks jump too easily.”

Convinced that I had a real problem, the scope was packed up and shipped to the manufacturer. So, was I hallucinating? Was my problem really just driver error? I’ve heard plenty of stories about guys who sent scopes in for repair, only to receive their optics back with a terse note saying: “Scope passed inspection and function test 100%. No repairs needed”. So, was my scope really FUBAR? You bet it was. When the scope came back from the factory, the Repair Record stated that nearly all the internal mechanicals had been replaced or fixed: “Replaced Adjustment Elevation; Replaced Adjustment Windage; Reworked Erector System; Reworked Selector; Reworked Parallax Control.”

How to Diagnose Scope Problems
When you see your groups open up, there’s a very good chance this is due to poor wind-reading, or other “driver error”. But my experience showed me that sometimes scopes do go bad. When your accuracy degrades without any other reasonable explanation, the cause of the problem may well be your optics. Here are some of the “symptoms” of scope troubles:

1. Large shot-to-shot variance in Point of Impact with known accurate loads.
2. Uneven tracking (either vertical or horizontal).
3. Change of Point of Impact does not correspond to click inputs.
4. Inability to zero in reasonable number of shots.
5. Unexpected changes in needed click values (compared to previous come-ups).
6. Visible shift in reticle from center of view.
7. Changed “feel” or resistance when clicking; or uneven click-to-click “feel”.
8. Inability to set parallax to achieve sharpness.
9. Turrets or other controls feel wobbly or loose.
10. Internal scope components rattle when gun is moved.

Source of Problem Unknown, but I Have a Theory
Although my scope came with a slightly canted reticle from the factory, it had otherwise functioned without a hitch for many years. I was able to go back and forth between 100-yard zero and 600-yard zero with perfect repeatability for over five years. I had confidence in that scope. Why did it fail when it did? My theory is side-loading on the turrets. I used to carry the gun in a thick soft case. I recently switched to an aluminum-sided hard case that has pretty dense egg-crate foam inside. I noticed it took some effort to close the case, though it was more than big enough, width-wise, to hold the gun. My thinking is that the foam wasn’t compressing enough, resulting in a side-load on the windage turret when the case was clamped shut. This is just my best guess; it may not be the real source of the problem. Remember, as I explained in the beginning of this story, sometimes scopes — just like any mechanical system — simply stop working for no apparent reason.

Permalink - Articles, Optics 6 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.
Permalink Optics No Comments »
June 10th, 2014

Save Fifty Bucks on Zeiss TERRA Scopes or Binoculars

Father’s Day (Sunday, June 15) is right around the corner. If dad enjoys hunting, here’s a way to save fifty bucks on a nice gift for the old man. Now through June 15, 2014, Zeiss is offering a $50.00 rebate on the TERRA 3X series rifle-scopes or TERRA ED Binoculars. The scopes offer 1/4-MOA clicks with a choice of standard Z-Plex or RZ6 or RZ8 ballistic reticles. Pick your power: 2-7x32mm, 3-9x42mm, 4-12x42mm, 3-9x50mm, and 4-12x50mm. CLICK Here for more details.

If you’re wondering about these binoculars, trust us, they are high quality. TERRA ED Binoculars feature SCHOTT ED glass — just about the best you can get. These binocs, in 8x42mm or 10x42mm versions, offer great low-light performance and a wide-angle field of view.

Zeiss Father's Day Sale

Zeiss Father's Day Sale

Permalink Hot Deals, Optics No Comments »