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...
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.
614136
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.
1177291
Depends on what your prescription is. The camera has a built in -3.0 to +1.0 diopter adjustment. You want to buy the one that will allow you to match your prescription.E.g. If you wear +2 prescription, get the +2 and dial it down by 1. You would only need the - if you have to go further than the -3 that is built in. However, I have found that I do not use the diopter. When I have my glasses off, the images on the LCD are blurry. So I shoot with my glasses or contacts, so I can still view the images on the LCD.Hope this helps you decide.Chris
2263148
with out the 3x magnifier I wanted the two dot easy to see . with out the 3x magnifier over two dots hard to see them . yeah with 4 dots and no &#9726;3x magnifier looks like a straight line. I dint want the weight and pay the extra cash. my friend has the 4 dot and 3x magnifier really nice set up. hope this helped you :)
676547
I don't know how to measure parallax, but at 25-30 yards, parallax is not a problem. I have excellent clarity throughout zoom range. Worth the money!
1238980
The equation for the volume of a sphere is: V=4/3 &#960;r^3 (that weird n should be "pie" as in 3.14159) Thus, the volume of a 60-inch in diameter (30-inch radius) sphere is as follows: V=4/3 &#960;&#12310;(30 in)&#12311;^3((&#12310;2.54 cm)&#12311;^3)/&#12310;(1 inch)&#12311;^3 (1 mL)/&#12310;(1 cm)&#12311;^3 (1 L)/(1000 mL)=1853 Liters But, the volume of the balloon will depend on the pressure required to fill the balloon because the recoil force of the balloon will increase as the diameter increases. Basically, the pressure inside the balloon will be much higher than the surrounding air pressure. And the balloon pressure will increase significantly as the balloon diameter increases and approaches its burst pressure. So, the equation will be: (P1 (at sea level))/(P2 (needed to fill the balloon) )=V2/(V1(at sea level)) I work with angioplasty balloons (those used to treat blood vessel narrowings) daily and the burst pressure in those balloons is between 8 and 25 atmospheres for compliant and non-compliant balloons. This balloon is a compliant balloon (meaning that it changes shape with various pressures), so I would guess that the burst pressure is less than 8 atmospheres - probably more like 4 atmospheres. Thus: Volume =(4 atm)/(1 atm) x 1853 L=7,400 Liters (at atmospheric pressure) But, no fear, you don't have to fill the balloons to full capacity. By filling the balloons to only 40 inches in diameter, the volume and pressure will be substantially less. By my calculations, only 1100 Liters. As far as this information, you know what they say about experts: They know more and more about less and less until they know everything about nothing.
998685
It says"Magnifier 2 5x ...". I believe the 2 is just part of the product name, there is no decimal point. A 4" lens diameter can't be 5x, they just can't make them. I even asked my eye doctor about ordering one from him. So I think the lens is a 1.5x with a 3x inset as the lower information on the page description says,. I sent mine back as the one I bought at a fabric store was better. I think you could find a 2x or 2.5x in a large lens with a 6x inset somewhere else. The around the neck batteries wear out very fast so you need rechargeable batteries for cost reasons.
625014
Don't use it much anymore. When I did, I tested it and found it doesn't make much diff. The thing is, it's field of view widens as it gets further away. So if you measure something that is very small from a longer distance, you'll get a bad reading. When I used it, I was measuring small packages 5x8 inches from a very close distance like 1-2 ft. Sorry I can't be more help.
727222
The CPC is listed as using 1.25" star diagonal. You should be able to use the 2" star diagonal in this kit to use the eyepieces in this kit. You will need to remove the 2" diagonal and reattach your 1.25" diagonal to use your 1.25" eyepieces.
1747
These numbers refer to the strength (magnification) of the lenses. Higher numbers magnify more.
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
2263147
with out the 3x magnifier I wanted the two dot easy to see . with out the 3x magnifier over two dots hard to see them . yeah with 4 dots and no ◾3x magnifier looks like a straight line. I dint want the weight and pay the extra cash. my friend has the 4 dot and 3x magnifier really nice set up. hope this helped you :)
57696
Do you mean size or prescription strength? As mentioned below they are adjustable in size, although very difficult to change size of nose bridge. As for the prescription, they come in negative values. My prescription is different in each eye. -2.75 and -3.75. I picked one in the middle -3.00. They are great.
1471639
It depends on both the scope and the eyepiece. While the Barlow will increase the magnification by that amount you don't want to exceed the resolving power of the scope since you'll lose image quality and not gain additional detail. There are web calculators available that can help you figure out magnification and resolving power.
21877
They are adult size with different nose pieces to make a more custom size. If you mean correction strength ask your eye doctor. My son is nearsighted, he needs a negative correction I got him -2.0
417913
I looked up the definition of diopter. It made NO since. The light has little rings to magnify and it is not all that good. It is a good light and I do use it to pull splinters and rearly read small things. I like it!!!
571851
no, it measures the light reaching the subject which is independent of the lens used. It gives you accurate light measurements either in e.v. units, or in f stops. f stops as a measurement of light are equivalent. Differing lenses will affect the depth of field, but the amount of light will be constant and not vary with the lens. Thus, f/1.4 on a 50mm lens will give you the same exposure as it would on a 100mm lens.