The Tasco Offshore Waterproof model OS36
Binoculars for the Budget Conscious

25 February 1999
By Scott Powers
The Tasco Offshore Waterproof Binoculars - OS54-1 - 
showing the Rubicon ruby coating, rangefinding reticle and compass

The Offshore Waterproof line of Tasco binoculars has been on the market for many years now. These large bodied but lightweight binos provide a surprising amount of clarity for the money. I must admit, again, to some bias against Tasco products (which may be one of the reasons why it has taken me two years to do this review!) Well, at the urging of our illustrious webmaster, it has been made clear to me that I have been derelict in my duty. So here it is.

When I first purchased my set, it was not called the Offshore. It simply went under the name Waterproof and the old model number was 322BCW. I was attracted to this binocular because it superficially resembled the Steiner Mk22. The Scout platoon at HHC 1/115th was blessed with that model and I wanted one badly. Being in the TOW platoon, I was stuck with an old battered Mk19 that was partially opaque! I had to get something better and when I saw this Tasco at a third of the price of the Steiner, my young mind said, "WOW!" Being in my late 20's at the time, the $199 price was right. The night I made the purchase, I took the binoculars outdoors and observed the sword in the constellation Orion's belt. There I was astounded to find that I could clearly make out the blur that is the Crab Nebula! Not too shabby for $199 I thought. Over the years, I have used this glass for many occasions -- astronomy, aviation events, sniper school, competitions, camping, bird watching (the two-legged kind mostly), and I have found them to be of surprising quality for the money. Not comparable to Europe's finest, mind you, but sufficient for the task at hand.

A General Description of the Offshore Waterproof Line

The current Offshore line comes in six models ranging from an 8x25mm to several 7x50mm offerings. The model closest to the older version I have is the OS36. For the purposes of this evaluation only, the 7x50mm OS36 and the OS54-1 models are of interest to the tactical shooter. Both of these have an internal red illuminated compass and a range finding reticle. They weigh in at 36.3 ounces and are approximately 5.75 inches long. The lenses are fully coated (multi-coated in the case of the OS54-1) and the BAK-4 prisms are of the porro prism type. The eye pieces are individual focus and adjust from +3 to -3 diopters. Both binoculars have a tripod adapter between the objective lenses. There is a small housing atop the right barrel that houses the compass light and battery. A sliding ring encircles the objective barrel of the left objective. This ring can be used to help calculate range based on meters, yards or feet. It is quite accurate when used with the internal reticle. The overall appearance of the binoculars is attractive and business-like. The binoculars are fairly light in feel and they balance well. Collimation between the two barrels is excellent with no apparent parallax. I have yet to suffer eyestrain while observing with this set. The eye relief is normal for this type of binoculars. If you wear glasses, you will have to roll back the soft rubber eyecups to get a full field of view. The field of view at 1000 yards is 366 feet. The Offshore line is dry nitrogen-filled and has internal O-rings to seal out moisture and fogging.

General Impressions

The OS54-1 is essentially the same as the OS36 except for the lens coating. Reminiscent of the Mk22 Steiner military binoculars, the OS54-1 has a brilliant objective lens coating that Tasco calls Rubicon. This fiery red lens coating improves contrast dramatically but is quite flashy. I believe the Steiner glass is coated in a laser reflective substance to protect the eyes of the soldier on the modern battlefield from the various laser ranging systems utilized today. Both of these coatings, for whatever purpose, are quite an attention grabber, and the addition of a Butler Creek Sport Flash filter is advised. Focus is simple. Just rotate each ocular in turn to achieve sharp focus. I prefer individual focus over the center focus or the so-called zip focus systems found on many glasses, in large part due to their propensity to go out of focus every time you adjust the barrels to fit your eye spacing. With the individual focusing system, once you set the ocular lenses, they pretty much stay put until disturbed.

Range finding

The range finding reticle of the Tasco Offshore, 
with the compass in the bottomThe range finding reticle provided in the OS36 and OS54-1 is somewhat of an oddity in that the distance between each tick mark works out to be approximately 12 inches at 100 yards. With this spacing, you can devise several methods of ranging if you chose not to use the provided ranging scale. If you are used to the mil formula, converting this reticle is a simple matter of breaking down each division tick to represent 3.3 mils (12" divided by [one mil] 3.6" = 3.3 mils wide). While this is not as fine as one might prefer, it is finer than the old 10 mil binoculars floating about in the military. With a little experimentation you can get a finer reading by breaking down the short vertical and horizontal ticks to fractions of a mil in the same manner as done with the artillery binoculars used in the military. These short ticks appear to be about 1/4 the length of the full distance between each hash mark. This would round out to be approximately .9 mils --certainly usable for range estimation.

If you choose to use the provided slip ring, ranging becomes a simple function of determining the height or width of the target in yards, meters or feet and reading off the corresponding range on the scale. The scale reads angular measurement and can be used with all three methods - feet, yards, or meters. The scale has 30 increments horizontally and 26 vertically. These are broken down into major divisions of 5 ticks each, represented by a longer tick mark. To simplify it, the scale covers 30 horizontal feet (10 yards) at 100 yards and each major division subtends 5 feet. There are numerals placed at each major division mark. This is important if you chose to use the provided scale as readings less than the numeral 1 are broken down into fractions. In other words if the object is only one tick wide you would call it an angle of 0.2 and if two ticks wide, you'd call it 0.4. Correspondingly, an object 6 ticks wide would be called 1.2. This is your ANGLE of measurement. It all sounds totally confusing but once you try it the method is pretty much idiot proof. Believe me it is harder to explain than to perform. These paragraphs took me an hour to write and yet the whole procedure takes a couple of seconds! Mom raised a literary idiot you see.

Ranging via the scale goes something like this. You are viewing a parked aircraft at the end of the runway. Its wings span 6 tick marks, or as the scale reads, an angle of 1.2. Take this angular measurement and move to the slip ring scale on the objective barrel. Slide the angle of 1.2 around till it is aligned with the provided mark, then find the known object size on the bottom of the ring. In this case the wing span is 32 feet or 10.6 yards. I find 10 yards on the scale and look at the distance reading provided below. The reading falls between 40 and 60 on the scale which is read in multiples of 10. Or in this case is approximately on the plus side of 50 or more accurately, 500 yards. The actual procedure takes about 5 seconds to do if you know the object size beforehand. As in all binocular ranging methods there is some room for error. I shall show this below by going to the more tedious but accurate mil method.

You can also range with the mil relationship, but you'll need your calculator. This time read each tick mark as 3.3 mils. Since the aircraft's wings subtend 6 tick marks, this equates to 19.8 mils (3.3 mils x 6 = 19.8 mils). You know the wings to be 32 feet wide which is 384". Multiply 384 times 27.7 and divide by the mils, which is 19.8. The answer is 537 yards. You can use the short cut method since the target is so big. Multiply 10.6 yards by 1000 and divide by 19.8 which equals 535 yards. As you can see, you can use several methods once you understand the reticle. It sounds far more complicated than it is. Welcome to the world of precision range finding. Fear not though -- by using the scale as designed and described in the binoculars instructions you can range without any math what so ever. I simply provided the mil method for those of you who want the range right down to the last yard.

Lens caps

Lens caps are provided with the binoculars. The objective caps are similar to the Steiner caps - each cap is attached to the center stud/tripod adapter. This is a nice feature, because you won't readily lose them in the field. I went one step better and ordered a set of Butler Creek flip-up caps for spotting scopes. Placed on each objective, I no longer worry about losing caps at all. The rear cap is trash. It is exactly like those found on many military style binoculars, the Steiner Mk22 in particular: a single rubber boot that fits over both ocular lenses and is retained on the neck strap. This is good for storage but nothing else. I guess there is little better on the market but they never seem to stay on the lenses when you want them to. Being of a specific width, they will only remain in place if the binoculars are spread out to fill that distance. If the barrels rotate together in your equipment bag or backpack, the ocular cap just falls off. I had to resort to a wide rubber band to keep the bloody thing in place. A small nit, but an annoying one.

The Tasco Offshore Waterproof Binoculars - OS36
Neck strap

The neck strap, as with most civilian binoculars, is just a thin ribbon of nylon. It was the first thing I tossed out. It'll dig right through you neck on a long walk. A perfect replacement is the strap provided with a military 2-quart canteen carrier. This can be worn over the shoulder or neck and is adjustable for length. At two inches wide, it is a vast improvement over most stock binocular straps. I used 550 cord to attach this strap to the body of the binoculars via the provided integral strap slots. This is a lot less noisy than the metal clips.

Internal compass

The internal compass can be viewed at the bottom of the right binocular barrel. It is fairly accurate. Tasco claims a +\-1 degree of deviation, which I had no way to accurately test. For what it is worth, the internal compass reads fairly close to my mil-issue Lensatic compass. The deviation was only a few degrees and either compass could have been the culprit. You can navigate with this compass if you are of a mind to. The compass is a nice feature -- one you might find handy in a pinch. I did rely on it once while on a four-wheel drive excursion into the wilderness. My lovely spouse lost my high dollar Lensatic on the trail. Having this compass as a back-up provided some much-needed piece of mind. As long as you keep the binoculars fairly level, the compass will function fine. Tipping up or down will cause it to lock up until you level the binoculars again. The cover housing over the compass is made of plastic. I tell you this because after 5 years, the housing cracked on my binoculars. This may have happened as a result of a drop of which I was unaware. When it happened, the light switch, which is located on the housing, froze up. I guess I get to test Tasco's limited lifetime warranty. I'll let you know the results as soon as I do. The hardest part of this breakage is parting with the unit. I use it frequently and care little about the nighttime illumination function. I have my tritium compass for night excursions.


The glass is of sufficient clarity to be usable in most situations. While the Offshore Waterproof might not compare to the Steiner's for total clarity and brightness, I have yet to find myself limited by this binocular. Whether observing targets in low light or scanning for targets in the bush, the large 50mm objectives provide plenty of contrast and light-gathering ability for the dollar. For the sniper, the size of these binoculars may be an issue. They are fairly light but like all 50mm glasses, they are somewhat bulky. They are not large but they are not as convenient as a 7x30mm set. The added advantage, of course, is the light gathering ability of the 50mm lens. With the larger lenses, long-term observation causes less eyestrain and the wide angle view makes the image appear less jerky.

Optics testing

The Optics were tested against a Zeiss Test Pattern set at 30 feet. See the example ZPT for clarification. The ZTP consists of 13 progressively smaller blocks. Each block is numbered and can be used for optical comparisons. I could resolve down to 12.5 on the ZTP which is just 5 blocks from the smallest square. I could make out some of the lines on the number 16 block, but it tended to blend into a solid. The no. 12.5 block measures about 1/4" and I could still resolve most of the individual lines. When moving the ZTP to the edge of the field of view there is some indication of curvature of field and spherical aberration. In other words the image loses focus. As this happens at the outer edges of the field I can live with it. The image is in perfect focus to about a third of the way to the edge. If you want better, you will have to pay more.

Zeiss Test Pattern for Optics

Both the OS36 and OS54-1 have fully coated lenses (a coating on all air-to-lens surfaces). These coatings are said to reduce internal reflection and help transmit light. The OS36 does not have the Rubicon Ruby coating. External reflections are reduced by the standard coatings, but you still must be aware of direct sunlight reflecting off the objective.

The Rubicon ruby coating provided on the OS54-1 is a 14-layer multi-coating process that filters out the red end of the spectrum to provide brilliant daylight viewing. This enhances contrast dramatically and is excellent for bright outdoor viewing. It is not as ideal for low light situations and you might be better served by the OS36.


As good buys go, the Tasco Offshore Waterproof binoculars are one of the better sets out there for under $200. You might certainly find a superior set, but you will pay accordingly for it.

Retail Price as of Feb. 1999:
OS36 - $199
OS54-1 - $230

Model :
OS36 and OS54-1
Power :
Objective :
FOV @ 1000 yards :
Focus System :
Prism Type :
Features :
Range Finding Reticle and Compass;
Fully MultiCoated;
BAK-4 Prisms;
Tripod Adapter Fitting;
Rubber Armored

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