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!
1503374
The 25 and 36 refer to the size of the lens opposite the eyepiece in mm. The larger the lens the more light it gathers. This of course makes for a heavier monocular and a larger one. I have a 10x25 and it is fine. You have to have a steady hand though in using the devise.
2071543
I physically measured mine using a digital caliper, it can only hold lenses with diameter 65mm safely.
1359655
To get the answer that you are seeking; I would go to www.nacdrops.com to get a definitive answer. My understanding of this product was specific to the eyeball penetration. Hopefully this will aid you in what you are requesting.
1120065
They adjust for interpupillary distance at the hinge. The adjustment is so wide, I can't imagine them not fitting everyone. Hold them up to your eyes and move them in and out until the two circular images merge into one. The interpupillary distance is set. Then focus them until the image in the left eye is sharp. If the right image is also sharp, the focus is done for that distance. If the right image is fuzzy, adjust the diopter ring on the right eyepiece until the right eye is also sharp. From then on, focus is done with the big wheel in the middle. Easy peasy.
1193218
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.
897742
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.
118248
I ordered about 3 month ago this model refractometer. I bought also one wine triple scale hydrometer (Specific gravity,BXº and % potencial alcohol).Comparing them,(hydrometer and refractometer) ,i found the relative wrong in BXº readings are so small as 1.5%,and Specific gravity are smaller than this. Comparing refractometer results readings with theorical values of one BXº vs. S.G setting chart,I found relative wrongs reachs up to 6.8%.
438324
These glasses actually do have a magnification of +.25. I actually took them to my eye doctor and they measured the power for me. To put this in perspective, many reading glasses are +1 magnification. +.25 is the smallest increment, incrementing at .5 .75 and 1. So, the magnification is quite small, it just helps things become a little clearer.
21876
goggles dont come in sizes but in styles. Its wathever feel more conmfortable to you, the adjustment is done thru the strap. If you are talking about prescription it is usually what your glasses prescription is if its different on both eyes go with the lowest prescription. otherwise you will feel disoriented.
2230132
All I know is that it refers to the unit of measurement of the optical power of the lens. I can't quantify the numbers, but this lamp magnifies very well.
377710
I not sure what you mean by 'strength'. I certainly do not have a spectrum analyzer or light meter to measure intensity and wave lengths from a specification perspective. What I can tell you is that I have prior experience with UV light in water supply systems and air vent systems and the results I have achieved with this device are consistent with these other better known systems/applications. Furthermore, like I posted, this is not a toy and should be handled as a tool. I also bought the UV glasses for eye protection, keep my skin out of the light ray, and keep me kids away when in use. One really good indication of it working is the 'ozone' smell associated with disinfected area. It is the same smell you get after a lightning strike. To find out how it works, I would suggest looking into water supply UV light systems. It takes very little exposure to UV light to kill bacteria that can be found in well water. I would be happy to share specific details if know the application for which you are considering this purchase.
1746
That is the strength of the reading glass. The higher the number the greater the magnification. It is not at all about the size as it will fit your head.
1679463
Its infinitely variable as far as I can tell. Its like twisting a knob.I don't use this very often, only on one particular lens. I almost forgot about it. Thanks for reminding.No issues with this at all. Just guesstimate only for aperatures.
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.
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!
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.