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 determine the strength in buying goggles? 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... » Read More 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 determine the strength in buying goggles? « Show Less
107802
That equation is correct... it is called spherical equivalent. With a -3.00 sphere and -3.25 cylinder, your spherical equivalent is -4.50. Keep in mind this will give you pretty decent vision - good enough to see at a reasonable distance, but this will not be equal to a full spectacle prescription. I am an optometrist.
40139
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.
107803
hi, none of us are opticians. I'd give them a call and ask. That way you'll get a pair of goggles that you can use to read underwater - haha - but seriously, I was thrilled when I could see clearly underwater. It's worth the effort!
1652323
Her is two thoughts, 1st you can use a minus 1 and that may give you the rsange you want but I took the 2nd way which I purchased a -2, that way I can use the plus adjustment to get the proper adjust. Don't to purchase an eye cup for the corrective lens.
967887
The magnifying strength is 3x, with a 5x, 1" bubble. I have never figured out how to use it to magnify my cross stitch cloth, only the pattern, which is still a great help.
847841
Sorry, Heather, I don't know the answer to that question. I was recently using my table saw when a piece of Cedar, about 1"x4" flew off the blade and hit my chest. It hurt like crazy. I was wearing eye-glasses but no goggles - lesson learned. I turned the saw off, vacuumed all the sawdust and didn't use it again until a few days ago when I received the goggles. My ... guess ... is they are osha approved. Hope that helps, and good luck.
1660679
As others have stated there is no magnification. The 1-4 I believe refers to the MOA size of the dot. 1 MOA for more precise aiming 4 MOA for faster sight aquisition. You probably already know this but 1 MOA is roughly equal to 1 inch at 100 yards, 4 MOA roughly 4 inches so the bigger the dot the more of your target is covered and the less precise your aiming. This is a very generalized explanation. Hope it is helpful.
1177290
It depends on what your eyeglass prescription is. I spoke to my optometrist to see Whart general range is.
439838
It is variable, from 1.75 to 5 - it depends on how far away the lamp is from the item: 1.75 if up close to the glass, 5x if a foot away - more than a foot away and focus begins to be lost. I use it for modelling and its about as good as it gets.
1190631
As per previous answer it is just standard adapter for a camera specific T ring so you can attach camera to telescope that has 1.25 eyepiece It will not give more "strength" (I assume you mean magnification).
1591412
This is a very complicated answer. I defer to this link.http://www.astroadventures.net/cohen/articles/Wear%20or%20Not%20to%20Wear%20Glasses.pdfWhether you wear glasses or not, each lens that you use requires that your eye be placed at an optimum distance from the lens. Wearing glasses prohibits one from getting one's eye close enough to enjoy the full field of view with some lenses but not others. The preferred method is to NOT wear glasses and each person must adjust the focus for the best clarity. If your wife has an astigmatism, you can switch to higher eye relief lens while wearing glasses or purchase Televue Dioptrx Astigmatism-Correcting Lenses while not wearing glasses. Have her optometrist make her a monocle. This is a very complicated answer. I defer to this link.http://www.astroadventures.net/cohen/articles/Wear%20or%20Not%20to%20Wear%20Glasses.pdfWhether you wear glasses or not, each lens that you use requires that your eye be placed at an optimum distance from the lens. Wearing glasses prohibits one from getting one's eye close enough to enjoy the full field of view with some lenses but not others. The preferred method is to NOT wear glasses and each person must adjust the focus for the best clarity. If your wife has an astigmatism, you can switch to higher... » Read More This is a very complicated answer. I defer to this link.http://www.astroadventures.net/cohen/articles/Wear%20or%20Not%20to%20Wear%20Glasses.pdfWhether you wear glasses or not, each lens that you use requires that your eye be placed at an optimum distance from the lens. Wearing glasses prohibits one from getting one's eye close enough to enjoy the full field of view with some lenses but not others. The preferred method is to NOT wear glasses and each person must adjust the focus for the best clarity. If your wife has an astigmatism, you can switch to higher eye relief lens while wearing glasses or purchase Televue Dioptrx Astigmatism-Correcting Lenses while not wearing glasses. Have her optometrist make her a monocle. « Show Less
1074584
Refractometer is really easy to use. If you have DI water source u can use it to calibrate. If not the calibration solutions are inexpensive.
294870
When you use it with the little white globe thing, you hold it up against your subject and read the light from there. That's really what this is for. You can also slide the globe out of the way and use it to measure reflected light, but that's going to be fairly inaccurate (since it is hard to point a meter like this with any degree of precision). But still, you point it at your subject, press the button, then look at the reading.
315445
I have held a ring with the stone facing down against the measuring opening. I get a reading but it fluctuates if I move the stone. With a faceted surface it's easier but I have gotten readings for cabochons. It's a good tool but of course not definitive. There are different stones that have the same refractive range...for example...quartz, amethyst, onyx, aventurine, citrine...so I think you have to make a judgment on the stone using other info too. I am not a professional gemologist. I use this tool as additional confirmation of what I think the stone is. I also like the presidium Gem tester. There's a lot of glass on the market...even set in gold! I have held a ring with the stone facing down against the measuring opening. I get a reading but it fluctuates if I move the stone. With a faceted surface it's easier but I have gotten readings for cabochons. It's a good tool but of course not definitive. There are different stones that have the same refractive range...for example...quartz, amethyst, onyx, aventurine, citrine...so I think you have to make a judgment on the stone using other info too. I am not a professional gemologist. I use this tool as additional confirmation of what I think the stone is. I also like the presidium Gem... » Read More I have held a ring with the stone facing down against the measuring opening. I get a reading but it fluctuates if I move the stone. With a faceted surface it's easier but I have gotten readings for cabochons. It's a good tool but of course not definitive. There are different stones that have the same refractive range...for example...quartz, amethyst, onyx, aventurine, citrine...so I think you have to make a judgment on the stone using other info too. I am not a professional gemologist. I use this tool as additional confirmation of what I think the stone is. I also like the presidium Gem tester. There's a lot of glass on the market...even set in gold! « Show Less
1677692
I'd say that this is more along the lines of a 'generally specific' more so than a 'literally specific' measurement. I'm sure you can find the right reading given enough time. This uses displacement to gauge the proof of a liquid so you'll have to be sure to let the hydrometer be free from the edges of its container and the water must be completely still. So yes, it will differentiate but you'll have to have a really good eye for it!
1213448
+3.5. And, besides: I tried them in a store and found that they they work superbly for adjusting on the fly between -6 and +3.5 correction (more or less). The optics seem excellent. As a fashion statement a bit awkward but hard to make the double lens system look better. The dial adjusters are discretely positioned and effective. I have no idea about durability.
1515978
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
866403
I haven't used it, bought it for a professional guide in Africa. Has a little square in the center to center the target with. Is 6x magnification, if I recall right, so does magnify the target. with that magnification, I'd put 400 yds, in a real steady hold, hand braced on something at 400 yds..maybe a bit less. everything is fog proof these days, and probably water proof,if you're talking rain..don't know about scuba diving with it. you might want to go to the Optics Planet site, as they have the breakdown on those things on their site.
743771
It's not a graduated cylinder that's for sure. Based on the overall diameter of the location you are taking a measurement I imagine it would be very hard to get consistent readings, just due to parallax. If you're looking for something super accurate, this isn't the right tool.