How to buy the best forestry prism?

The Donegan OptiVISOR is a hands-free, headband binocular magnifier that has optical glass lenses that are ground and polished into prismatic lenses for quality and clarity, and is available in multiple dioptric strengths (indicated by the number in the model) which provide specific magnification power (X) at specific focal lengths, or distance from object. This magnifier enhances the size and resolution of an object or image, and is commonly used for a variety of applications such as jewelry-making, watch- making, needlework, artwork, electronic inspection, book-reading, print inspection, and stamp-collecting.

The OptiVISOR magnifier features replaceable binocular lenses that have beveled edges that are mounted in an interchangeable plastic frame. An adjustable headband with padded leather comfort band conforms to a variety of head sizes and provides comfort for hours of continuous use. It can be worn over prescription or safety eyeglasses. A durable, plastic visor tips up above the forehead when not in use. Spring-loaded pivot screws hold the headband in a raised or a forward-facing position. The magnifier weighs 0.67 lbs., and comes housed in a protective shell and carrying case. It has a one-year limited warranty. Diopter (D) is a technical term for the measurement of the light curvature and thickness of a lens. A dioptric number and a magnification number are not the same thing. Diopter strength represents a specific magnification power (X). For example, a 5-diopter provides 2.5X magnification (at a distance of 8). See the magnification chart. The higher the diopter, the more magnification a lens can provide. As magnification increases, distance to the object (focal length), and field of view (diameter, or narrowness of view) decreases. Magnifiers and prescription eyeglasses have a diopter value, such as 1.5 or 2. The dioptric strength of an accessory lens, such as prescription eyeglasses or an eye loupe, must be added to the dioptric strength of the magnifier to calculate total magnification. Magnifiers are devices used to enlarge the visual appearance of an object or image. Magnifiers come in a variety of styles such as hand-held, headband, standing, clip-on, eye loupe, and those that hang in a necklace form, or fit in a trouser pocket. Magnifiers are commonly made of plastic or glass. They can have one or more lenses with varying magnification abilities, and can have a binocular configuration with a single lens, or two separate lenses. They are sometimes used with LED or fluorescent light sources to help control viewing capabilities. Magnifier ability is often expressed as magnification at a specific length. For example, 1.75X at 14 means that when a magnifier is held at 14 from a viewers eyes, the object will be magnified 1.75 times (X) its actual size. As magnification increases, viewing areas and focal length decrease. Magnifiers sometimes have a diopter number, expressed as + or -D, which is a measurement of strength (or power) of the lens. Some magnifiers are marked with a dioptric number on the lens. A high diopter number has a higher magnification than a low diopter number. Aspheric magnifiers, unlike spheric magnifiers, produce a sharp image to the edge of the lens for less distortion. Magnifiers are widely used in jewelry inspection and fabrication, watch-making, needlework, artwork, reading, print inspection, and stamp-collecting.

Determining Magnification Diopter Magnification Focal length (Distance from object) Sample view 20/20 vision 20" (50.8cm) 2-diopter lens 1.50X 20" (50.8cm) 3-diopter lens 1.75X 14" (35.56cm) 4-diopter lens 2.00X 10" (25.4cm) 5-diopter lens 2.50X 8" (20.32cm) 7-diopter lens 2.75X 6" (15.24cm) 10-diopter lens 3.50X 4" (10.16cm)

Donegan Optical manufactures and distributes precision visual devices for hobbyists and professionals in industry, home, office and crafts applications. The company was founded in 1952 and is headquartered in Lenexa, Kansas.

Whats in the Box?

• OptiVISOR
• Fitted, plastic, carrying case
• Instruction manual

The VEE GEE STX-3 is a handheld, portable, water-resistant salinity refractometer that measures salt concentration in parts per thousand (PPT) in the 0 to 100% range and specific gravity (SG) of seawater in the 1.000 to 1.070 range, has automatic temperature compensation (ATC), and a durable metal body with rubber grip. A salinity refractometer measures the concentration of salt, such as sodium chloride, magnesium and calcium sulfates, in liquids and displays the results. Handheld refractometers, also known as sugar meters, concentration meters, or Brix meters, are commonly used in the culinary, food and beverage, pharmaceutical, educational, geological, chemical, and ecological industries, and for water-testing applications.

This refractometer is housed in a durable metal body. The VEE GEE STX-3 features ATC for immediate, accurate readings, with an ambient temperature of 10 to 30 degrees C. The unit is factory-calibrated and can be calibrated with distilled water. Calibration can be controlled and adjusted with a tool-free calibration ring and a set screw. The outer shell is rubber coated with dimpled grip for easy gripping and the rubber coating guards against hand heat for accurate measurements. A non-roll stand prevents the unit from rolling when placed on a flat surface such as a table or bench top. The optical glass prism is mounted in an all-metal housing composed of copper alloy with a nickel-chrome coating for quick temperature equilibrium between the sample and the prism. The analog Brix scale features a bright, high-contrast display for clear visibility of the boundary and memory lines intersection. Instantaneous sample readings illuminated by ambient light are viewed through a monocular, focusable, cushioned eyepiece. The unit comes with a zippered vinyl carrying case, a plastic transfer pipet and an instruction manual.

Specifications

H is height, the vertical distance from the lowest to highest point; W is width, the horizontal distance from left to right; D is depth, the horizontal distance from front to back.

Refractometers are used to determine substance content in a sample, to provide unit readings of substances including Brix, salinity, and alcohol; to detect chemical impurities, or to measure components of samples such as industrial fluid. Refractometers measure the refractive index of a substance, which is its optical characteristic, and the number of dissolved particles in it. The refractive index is the ratio of the speed of light in empty space to the speed of light in a substance; when light passes from one medium to another. Generally, a low concentration sample has a larger angle of refraction than a high concentration sample. For example, a straw placed in a high-concentration substance appears more bent than when placed in a low-concentration substance. Refractometers can work with natural light, or with an external power source such as batteries or electricity. They typically have either a digital or analog reading display, though some units utilize both types. Some analog-display refractometers can be used for both solids and liquids. Digital-display refractometers are used exclusively for liquids. Types of refractometers include handheld, benchtop, and in-process. Handheld refractometers are elongated and telescope-shaped, or shorter and rectangular. Analog handheld refractometer readings are obtained by looking through the monocular eyepiece and viewing where the boundary line intersects with the memory line. Digital handheld models provide a digital readout. Benchtop refractometers typically measure with a higher degree of accuracy than handheld units. In-process refractometers are used for continuous process monitoring and data readouts, and are generally fitted into a piping system for ongoing analysis. Refractometers are used in a wide variety of applications in the culinary, food and beverage, pharmaceutical, educational, geological, chemical, ecological, and automotive industries, and for water-testing applications.

VEE GEE Scientific manufactures laboratory equipment and supplies, and makes the VanGuard brand of products. The company, founded in 1981 and headquartered in Kirkland, WA, offers scientific equipment for educational, research, clinical, and industrial applications.

Whats in the Box?

• STX-3 refractometer
• Vinyl carrying case
• Plastic transfer pipet
• Instructions

The VEE GEE BTX-1 is a handheld, portable, water-resistant sugar refractometer with a Brix scale that measures in the 0.0 to 32.0% range, is powered by ambient light, has automatic temperature compensation (ATC), an optical glass prism, and a durable metal body with rubber grip. A Brix refractometer measures the refractive index of a solution in a sample, converts it to sugar concentration in units of percent by weight (% Brix, also known as degrees Brix), and displays the results. Handheld refractometers, also known as sugar meters, concentration meters, or Brix meters, are commonly used in the culinary, food and beverage, pharmaceutical, educational, geological, chemical, and ecological industries, and for water-testing applications.

This refractometer is housed in a durable metal body. The VEE GEE BTX-1 features ATC for immediate, accurate readings, with an ambient temperature of 10 to 30 degrees C. The unit is factory-calibrated and can be calibrated with distilled water. Calibration can be controlled and adjusted with a tool-free calibration ring and a set screw. The outer shell is rubber coated with dimpled grip for easy gripping and the rubber coating guards against hand heat for accurate measurements. A non-roll stand prevents the unit from rolling when placed on a flat surface such as a table or bench top. The optical glass prism is mounted in an all-metal housing composed of copper alloy with a nickel-chrome coating for quick temperature equilibrium between the sample and the prism. The analog Brix scale features a bright, high-contrast display for clear visibility of the boundary and memory lines intersection. Instantaneous sample readings illuminated by ambient light are viewed through a monocular, focusable, cushioned eyepiece. The unit comes with a zippered vinyl carrying case, a plastic transfer pipet and an instruction manual.

Specifications

H is height, the vertical distance from the lowest to highest point; W is width, the horizontal distance from left to right; D is depth, the horizontal distance from front to back.

Refractometers are used to determine substance content in a sample, to provide unit readings of substances including Brix, salinity, and alcohol; to detect chemical impurities, or to measure components of samples such as industrial fluid. Refractometers measure the refractive index of a substance, which is its optical characteristic, and the number of dissolved particles in it. The refractive index is the ratio of the speed of light in empty space to the speed of light in a substance; when light passes from one medium to another. Generally, a low concentration sample has a larger angle of refraction than a high concentration sample. For example, a straw placed in a high-concentration substance appears more bent than when placed in a low-concentration substance. Refractometers can work with natural light, or with an external power source such as batteries or electricity. They typically have either a digital or analog reading display, though some units utilize both types. Some analog-display refractometers can be used for both solids and liquids. Digital-display refractometers are used exclusively for liquids. Types of refractometers include handheld, benchtop, and in-process. Handheld refractometers are elongated and telescope-shaped, or shorter and rectangular. Analog handheld refractometer readings are obtained by looking through the monocular eyepiece and viewing where the boundary line intersects with the memory line. Digital handheld models provide a digital readout. Benchtop refractometers typically measure with a higher degree of accuracy than handheld units. In-process refractometers are used for continuous process monitoring and data readouts, and are generally fitted into a piping system for ongoing analysis. Refractometers are used in a wide variety of applications in the culinary, food and beverage, pharmaceutical, educational, geological, chemical, ecological, and automotive industries, and for water-testing applications.

VEE GEE Scientific manufactures laboratory equipment and supplies, and makes the VanGuard brand of products. The company, founded in 1981 and headquartered in Kirkland, WA, offers scientific equipment for educational, research, clinical, and industrial applications.

Whats in the Box?

• BTX-1 refractometer
• Vinyl carrying case
• Plastic transfer pipet
• Instructions