I read on another site that: 1/2 the cylinder measurement + the sphere measurement = diopter strength. Because I have a lot of astigmatism this changes the measurements quite a bit (-3.25 cylinder, -3 sphere). Has anybody else used this equation to...
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That's the method we used when buying my daughter's goggles. She ended up with -3.625 (R) and -4.25 (L) so we split the difference with a -4 prescription. She says they work well enough for her, and she has to be read a white board to get her workout during swim practice.
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The distance from the center of the 15mm rod to the center of the lens opening is adjustable between about 3.75 inches to 4.5 in. You just need to take a ruler to your rig and see if this your distance falls within that range. I got my matte box out and measured it. I just hell up a ruler so I could be off a little.
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Because of the difference I would suggest buying 1 pair in each of the diopters you need and swapping out the lenses. For me the difference was only 1 point so I went up a half. They've worked out great.
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I am actually hesitant to answer this question, because obviously no one here read the product description. On the first line it states "8 1/2-10 1/2" eye relief". So 10.5" at 2x, and 8.5" at 7x.
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After using it, you can inspect it with a magnifier. I saw no problem and continued to use it on my lenses and filters. I'm happy with mine.
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A 6mm eyepiece will give you about 75x magnification. I get better views of Jupiter in my scope with 4mm and 3.8mm eyepieces at about 115x. I don't like using a Barlow.
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I ordered the mask for my girlfriend who is near-sighted. She gave me a copy of her prescription. Under the "Dist" part of her prescription, sphere is -8.5 which is the number I used when I placed my mask order. I am assuming "DV" is distance, and "NV" is near. If so, I believe you would enter the "DV" number. The mask worked great for my girlfriend. She said she could see better out of the mask than her glasses. Hope that helps, Brian H.
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Paul, thank you. From the specs alone, I agree, but I think there must be some significant difference between the two sets. The only thing I can see from the specs is something about the eyepiece adjustment.
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No lenses do this.An f2.8 lens when racked out from infinity to 1:1 magnification is by definition working at f5.6.The number is the ratio of the distance from the sensor to the aperture divided by the diameter of the aperture.At infinity the aperture is basically 105mm from the sensor (simple lens approximation).At 1:1 the aperture is basically 210mm from the sensor.So the aperture is roughly halved.http://en.wikipedia.org/wiki/F-number#Working_f-number
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Hello; This is an 8 diopter lens. A diopter changes the focus range of your lens. Diopters come in powers from +1 to +5 (that I've seen). They're also stackable: you can put a +4 diopter on top of another +4 diopter, and conveniently that gives you the effect of a +8 diopter. (Quality does suffer when you stack.) The higher the number, the more powerful the diopter. The more powerful the diopter, the closer you can focus. Specifically: divide 100 centimeters by the diopter power. That's the maximum focus distance of the diopter. A +5 diopter focuses at 20 centimeters or less. A +2 diopter focuses at 50 centimeters or less, so an 8 diopter lens would focus around 13 centimeters or less. Hope this helps. Remember, this lens works when you are in full telephoto.
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The distance between the center of the pupils when focused on infinity (Interpupillary Distance)is not given in any of the specs for these binocs.Jim
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I have been satisfied with my refractometer so far. I previously had one that came in a gem lab I purchased 25 years ago and it wasnt nearly as easy to read as this one. No complaints to this point.
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Not at all. From the description, it is supposed to help people with imperfect vision. I found it pretty useless as I have 20/20. It further seemed like I was looking down a paper towel roll. I am very interested in their other magnifier which can work with a variety of others. Primary Arms makes one but I haven't seen any side by side comparisons.
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I have found no differences between the different diffraction glasses that I have purchased from Amazon. I have been buying large quantities for a couple years now to pass out to 8th grade science students in an Expanding Your Horizons project that I volunteered for. We use them to describe how Optical Emission Spectroscopy works in our lecture called "Chemistry of Light" I have never even tried them under black light, but will look into that for future reference. Not sure about the actual diffraction grating sizes being used but we are just looking to get the children's interest sparked so we haven't been very scientific about it. I have found no differences between the different diffraction glasses that I have purchased from Amazon. I have been buying large quantities for a couple years now to pass out to 8th grade science students in an Expanding Your Horizons project that I volunteered for. We use them to describe how Optical Emission Spectroscopy works in our lecture called "Chemistry of Light" I have never even tried them under black light, but will look into that for future reference. Not sure about the actual diffraction grating sizes being used but we are just looking to get the children's interest... » Read More I have found no differences between the different diffraction glasses that I have purchased from Amazon. I have been buying large quantities for a couple years now to pass out to 8th grade science students in an Expanding Your Horizons project that I volunteered for. We use them to describe how Optical Emission Spectroscopy works in our lecture called "Chemistry of Light" I have never even tried them under black light, but will look into that for future reference. Not sure about the actual diffraction grating sizes being used but we are just looking to get the children's interest sparked so we haven't been very scientific about it. « Show Less
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The 1.25 dimension is the standard telescope eye size for most scopes. I to have a C90 and purchase a "hybred-diagonal" (.965 to 1.25). This allows me to use all of my 1.25 eye pieces on my C90. Hope this helps.
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Some people with an astigmatism will see more than one dot or the dot will seem out of round. I am one of those people and you just get use to it over time. My aimpont and delta point do the same thing.
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What I did was, using a set of metric vernier calipers measure the outside diameter of bothe the Ocular lens (eyepiece) and the objective lens. Then using the Butler creek measurement table, chose the size as close too or slightly smaller than that measurement. I too had issues with finding what I needed and I did have to surf about a bit, but I finally found a table that had all of scope cap sizes and measurements. Hope this helps