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How Important is Your Eye Health?

Lack of eyesight can deprive a man from performing some vital activities of life. Tasks like reading are driving are virtually out of question... and living a normal life enjoying all the amenities becomes very difficult. One has to depend on others to perform even the simple task of crossing the road. It's very important that you take proper care of eyes which are your windows to the world. In Eye care lab dot com, you'll get all the information needed on how to keep your eyes healthy and treat eye problems. To take care of your eyes, the first thing you'll have to learn is how they work.

Your Eyes

The most common analogy drawn to the eye is with a camera. It is actually the body's very own camera...its parts doubling up as shutters, films and lenses to give you your vision. The pupil can be compared to the shutter through which light enters the eye. The light that enters the retina sends an inverted image to the brain which then forms the actual image.

This seems rather easy, doesn't it? Anatomically, the eye is much more complex than the normal camera! The eye is made up of several different, minute parts each of which perform different functions, all of which are equally important. The working principle of the eye is a very complex and lengthy process so let's not go into the biology lesson all over again! But the eye consists of several fluid-holding glands each of which is responsible in protecting the eye from physical injuries and providing lubrication without which the eye would run dry.

For example, the tear glands constantly keep the eye wet and also protect it from dust particles that can harm the eye. There is also a complicated system of nerves which send sensors to the brain, and also keep a track on irritating sensations in the eye. The muscles within the eye are also intrinsically connected with the functioning of the eye. All in all, the eye is truly one of the most complicated organs of our body...and the one which requires most protection.

Eye Problems

Like the proverbial "prevention is better than cure", the best cure for blindness is, you guessed it.....to keep it at bay forever. A healthy eye care regime demands regular appointments with an ophthalmologist who can keep a check on any problems and prevent common eye disorders from assuming a greater proportion. Eye care may also include a healthy diet comprising a lot of vitamin A rich foods.

Regular eye examinations also reveal the cause of any vision problems and also determine whether your eyesight requires any kind of corrective measures. Early detection of eye problems can prevent, and cure many diseases, including age related vision problems. The eye problems we've all faced are conjunctivitis and sty...both of which can be really painful and can sometimes be very prolonged. The more serious diseases are glaucoma and cataract that can result in permanent blindness if not operated or treated quickly.

Refractive errors of the eye are very common. They are known as farsightedness, people suffering from which cannot see things which are near, and nearsightedness and individuals having this vision error cannot see far away.

The cause for shortsightedness is that the suffering person from it cannot focus on objects that are far away. The corrective measure of this vision error is simply using a concave lens before the eye. In the same way, longsightedness is when a person cannot see objects that are near. This in turn can be corrected by using a convex lens. Vision disorders after the age of forty which occurs due to loss of elasticity in eye muscles is also very common and is known as presbyopia. This can be corrected by the use of bifocal lenses.

These visual errors and diseases are crucial and need to be treated correctly and before they cause serious damage. Our website will give you all the information you need about better eye care. It also contains articles on contact lenses, eye surgeries...in short, all that you'll need to know about your eyes and their problems. There is also a section on vision correction using laser techniques and laser operating procedures that use the newest, sophisticated laser techniques to treat eye disorders and correct them in a much better way than normal surgery, which is often risky and can result in causing more damage.

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Hubble's View Of The Universe [Part 1]

Hubble's View Of The Universe [Part 1 of 10] THE HUBBLE TELESCOPE Hubble works on the same principle as the first reflecting telescope built in the 1600s by Isaac Newton. Light enters the telescope and strikes a concave primary mirror, which acts like a lens to focus the light. The bigger the mirror, the better the image. In Hubble, light from the primary mirror is reflected to a smaller secondary mirror in front of the primary mirror, then back through a hole in the primary to instruments clustered behind the focal plane (where the image is in focus). THE UNIVERSE Hubble's longest exposures are like a core sample of the universe, recording galaxies at many different distances. This is one of the deepest core samples ever taken. It shows a few nearby stars in our Milky Way galaxy. The rest of the objects are distant galaxies, extending from 1 billion to over 10 billion light-years away. STARS Stars live and die over the course of millions to billions of years. It is unusual to see changes in individual stars. To learn more about them, we must piece together snapshots of stars at different life stages — from birth to death. The birth, life, and rebirth of stars is an ongoing process in the universe. The byproducts of this process include planets and the elements that make life possible. GALAXIES Galaxies come in diverse shapes and sizes. NGC 4414 — which is located about 62 million light-years away — is an example of a spiral galaxy. As with most spirals, the central ...

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Types of Binoculars

Binoculars are used for viewing distant subjects. It has two identical and aligned glasses in the same direction. It comes in different types and styles, serving different purposes.

"Binocular" comes from the Latin word "bini" which means "double," and "oculus" meaning "eye." The advantage of using two eyes with the use of this gadget is that it gives a wider view.

These gadgets are more commonly used by astronomers, hungers, navigators, sports fans watching a game, travelers, and militaries.

Different types of binoculars:
o Galilean binoculars - this binocular has the advantage of giving erect images. However, its capability of viewing wider images is limited. It cannot be used for high magnification. It also has two eyepieces, a convex objective and a concave eyepiece lens.

o Porro prism binoculars - the inventor Ignazio Porro, an Italian optician, designed this binocular. He used objective lenses separated off-set from the eyepiece. This maintains a folded optical path for wider and clearer views.

o Roof prism binoculars- this was designed by Achille Victor. This features an erected image. It also folds the path, making the object aligned with the eyepiece.

o Porro vs. Roof prisms - this was made for reducing the light transmission to about 12%. Porro prism binoculars also give brighter images. However, this binocular also features a similar magnification object size and optical quality.

Binoculars are useful in many fields. In astronomy, specialized lenses and gadgets are being used to enlarge and emphasize very distant objects from the sky.

Binoculars started in the 1970s and became must-have gadgets almost instantly. Some prefer buying branded ones with trusted quality and durability. What is important however is to be knowledgeable about the varieties to make sure you are buying the right model.

Check the magnitude of the glass surfaces. Some coatings are designed to reduce the glare of a bright light, as seen through the eyepiece. The common magnification is 7x50 or 8x25. The first digit refers to the number of zoom you can do and the second is the distance or the diameter from the front object you are attempting to view.

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Samsung 50-Inch 1080p DLP HDTV Review

Are you thinking of buying a Samsung 50-inch 1080p DLP HDTV?

This is a popular DLP HDTV model, and is a bestseller in many different shops. It has been around for just over half-a-year, and the customer base and comments has grown enough that we can now get a good feel for its pros and cons. I've consolidated a number of customer reviews from around the net. Overall opinion is that HDTV model is good and cheap, but not perfect.

Here is a useful rule of thumb: If you want to buy a HDTV, find out the watching distance in feet and multiply that with 5. That's the size of the screen you need. For example, if your watching distance is 10 feet, 10 times 5 is 50. So choose a 50-inch TV.

Good Points

Even when Samsung 50-inch 1080p DLP HDTV first came into the market, it was one of the cheaper 50-inch HDTVs. Now that the model is half-a-year old, it is even cheaper if you buy it from online retailers like Amazon. You are likely to see about $500 of savings off the list price. You also save on certain taxes and shipping costs. Additionally, if you find that the price has dropped between the time you bought the TV and the time you received it, you can ask the retailer to refund the difference. Reputable companies like Amazon actually honor such requests.

Although electronics tend to become obsolete quickly, this HDTV was leading edge when it came out. It already had 1080p resolution - many broadcasters are still catching up to this latest standard. Even now, its technology is quite advanced, and will likely remain so for the next few years.

Samsung 50-inch 1080p DLP HDTV uses an advanced technology called LED light engine. What it means for you is that the pictures are clear and detailed, and the colors look natural and true. Movement and action is much better rendered compared to normal LCD technology, and you won't see blurring or loss of detail. This HDTV also does well in bright rooms with considerable daylight penetration.

The built-in 2-speaker surround sound is of good quality. Do make sure the surround sound mode is turned on. HD broadcasts received over a simple, cheap, indoor antenna look great. Other content (Regular DVDs, SD/HD broadcasts, Nintendo Wii, DVD, Xbox 360, etc.) also look fantastic.

You probably already know its dimensions: 45.2"(W) x 31.8"(H) x 13.4"(D) 61.3 Lbs. This 50-inch DLP HDTV is thinner than many of its competitors, and is light enough for 2 persons to move around.

There are abundant connection inputs for HDMI, S-video, RGB component, digital, optical and analog sound, and RCA jacks, and they are located on the right side of the set for convenient access - this makes it easy to hook up. Unfortunately, this can be an issue if you place your TV in a cabinet.

Samsung 50-inch DLP HDTV is pretty user-friendly. The user manual is good and extensive (although not written for novices). The remote is intuitive and the menu system is straightforward. Note that it may not have as many functions as more expensive systems.

Its pretty quiet, since it uses LED light sources instead of the more normal bulb and color wheel of most other DLPs. Since the LED engine is cooler and more energy-efficient than the bulb and color wheel, Samsung 50-inch DLP HDTV also doesn't need a powerful cooling fan. Overall, you get good energy savings - it is Energy Star rated. Another good point is that the LED lasts longer than the bulb of normal DLPs (which need to be changed every 2 or 3 years).

Some of you might be nervous about getting faulty goods by buying from online retailers. The big and reputable companies like Amazon usually have a 30-day guarantee period. When any problems crop up, they have a good reputation of honoring their commitments to replace or refund the TV. If you are not certain about your online retailer, you can check their reputation with the Better Business Bureau.

Problems Encountered By Customers

Buying this DLP HDTV is not perfect, though. Customers have reported 3 main kinds of problems.

1) Delivery & Service Problems:

a) Some customers complain about not receiving their TVs. This is more likely to happen with online retailers with their more complex supply chain and delivery procedures - either their orders were not received by the vendor supplying the TV to the online retailer, or the delivery agent did not receive the correct delivery from the vendor, etc. There are precautions you can take to minimize problems (see the section below).

b) Sometimes you get an incompetent or lazy deliveryman. He may not be able to find the place you live. Or he may not want to deliver to your doorstep. Or he may just drop your TV off at your doorstep and refuse to carry it in for you. On the other hand, there are also stories of deliverymen who go beyond the call of duty - they help you to move your old TV to its new location, then they bring your new Samsung 50-inch 1080p DLP HDTV in and install it for you. Then the even take away the packing crate for you. Sometimes they do it for free, sometimes you have to pay them a few bucks extra.

c) There are also some complaints of poor customer service from Samsung. It is typical of any large company's service - when you get a good Customer Representative, you get good service. It helps if you get their name ahead of time before you start telling them about your problems or asking them questions. If you get a jerk, you get lousy service. Don't get mad, get their name, and escalate to their boss. If that doesn't work, get a refund or replacement from your retailer.

2) Quality Control Problems affecting some individual TVs:

a) The dreaded "blue-halo" effect, which basically is a blue-ish area of light that becomes visible in dark areas of high-contrast scenes, around the lower center of the screen. This seems to be caused by a ring around the lens of the projector that should be black, but is reflective silver in some TVs.

b) There is a "hot" or bright spot in the middle of the screen and the center is a little brighter than the edges.

c) When the entire screen is one color, sometimes the four corners of the TV fade in brightness.

d) The image is skewed (left side lower than the right), there is a noticeable green tint that is not correctable via any of the user settings.

e) Picture shuts off for minutes or hours at a time - which can be a motherboard problem.

f) Spots on the screen - which can be an unfixable LED light engine problem.

If the problem crops up well within the online retailer's guarantee period (typically 1 month), then call Samsung customer service and they will send a technician in about 2 working days to fix the problem. Otherwise, make good use of your retailer's guarantee period to get a replacement. Reputable online retailers like Amazon are pretty good about honoring their guarantees without hassling their customers.

3) Problems with the model or DLP HDTV technology which affect all TVs:

a) SD images via digital cable (connected via HDMI) are sometimes a little pixellated.

b) Small amount of curvature on horizontal lines right at the top of the set (which is a common artifact with this type of set) - not generally noticeable.

c) Minor incompatibility with 480p resolution settings and DirecTV (call your DirecTV customer service to get some satellite technicians to figure this out)

d) Echo if you have both TV speakers & surround sound speakers on and the volume is high. Just mute the TV, or use 5.1 or 7.1 surround sound.

e) When viewing non-HD programming in 4:3 mode there are a set of double lines at the edge of the image. This may be too distracting for some people.

f) When playing a letterbox or widescreen DVD the 16:9 or Zoom settings are a little off. The center of the image at the top is nearly 3/4 inches lower than at the ends creating a slight "U" shape or concave appearance. This can also be very distracting for some people.

g) Slight geometry problems (noticeable bowing towards the top center portion of the screen)

h) On non-stretch mode with SD (where you have a black bar down each side of the picture), the sides of the image are bowed in a little bit.

i) Viewing angle is limited, which sucks if you have a large number of people gathered around it. Just make sure that you're in the center and can see the screen. The viewing angle is good to about 140 degrees, although it is best up to 90 degrees. Still, this is supposed to be the normal level of performance for DLPs. Basically, the best seat is the sofa in front of the TV, although anyone on the love seat has just as good a picture.

Precautions To Take

1) If you buy from an online retailer like Amazon, make sure the TV is sold directly by Amazon. Amazon sometimes acts like a storefront for other companies. This means that you are the other company's customer, not Amazon's. How can you tell? Look for this sentence on the 1st page after Amazon lists the "Price" of the TV - "Availability: In Stock. Ships from and sold by Amazon.com." Other online retailers should have something similar.

2) Print the receipt. Although this is common sense, sometimes we forget. Or something else happens, for example, your printer breaks down. If this happens, just take a screen capture and save the picture to Microsoft Word.

3) Remember: You are probably buying online to take advantage of lower costs and free shipping. Don't expect 5-star service. Take the initiative to find out the contact of the actual supplier and delivery agent so that you can keep track of your order and delivery. Call the online retailer's customer support if you have any doubts.

4) If you think there is a problem with your Samsung 50-inch 1080p DLP HDTV, take advantage of the 30-day guarantee period to get a replacement or refund. Don't suffer problems for 3 months before complaining. By this time, it is too late.

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3 Types of Telescopes - Know the Differences Or Risk Buying the Wrong One

There are 3 main types of telescopes and each one performs differently and may be used for different purposes. If you are thinking about buying a telescope to look at stars and deep space then you should know that this might not be possible if you live in a built up area with light pollution. If it is just the moon and the planets you want to look at then you should now that refractors are better than reflectors for this. If you are prepared to travel with your telescope then you should know which types are fragile and which ones give you the best performance from a smaller scope.

The three types of telescopes that exist for capturing light so that it may be magnified for viewing are Catadioptric, Newtonian Reflector and Refractor.

Refractor Telescope

The traditional long-tube looking telescope. The Refractor uses lenses to bend light and this causes the rays to meet at a point on the other end of the telescope. They are magnified by the eyepiece for viewing. There is a large lens on the front of the Refractor, which is the objective lens.

Pros

Requires little to no maintenance
Excellent for planetary viewing

Cons

Color deviation in achromatic designs
Not recommended for deep sky observation

Reflector Telescope

The Newtonian Reflector uses a primary mirror that is concave. This mirror sends light to a flat mirror which reflects the light out a side opening and to the eyepiece where it is magnified and focused.

Pros

Best for deep space observation - Great for looking at remote galaxies
Delivers very bright images

Cons

Requires regular alignment
Requires more complicated cleaning of mirrors than other types of the same design

Catadioptric Telescope

The last of the three types of telescopes and currently the most popular on the market. This type uses a series of lenses and mirrors that fold the light path and send it through to the primary mirror through a small hole. This allows the light to be magnified and focused for viewing. There are two types of Catadioptric telescopes - Schmidt-Cassegrain and Maksutov-Cassegrain. The Maksutov type has a concave and convex correcting lens where the light enters. The light hits the primary mirror, is sent back to the secondary mirror and finally sent to the opening in the back of the telescope.Pros

Portable and easy to use
Versatile - good for deep space and planetary observation
About the best for focusing
Excellent optics

Cons

It does not look like a telescope to many people
It is more costly than other Newtonians with the same size opening for light

Once you know what you want to look at and which of the types of telescope you should choose you need to think hard about how much you are prepared to carry around, telescopes can be bulky and your tripod and mount are essential bits of additional kit. Size determined, you are now ready to see just how much aperture you can get for your money. Don't concern yourself with magnification, it is not nearly as important as is touted and higher magnifications will cause images to be blurry because of air turbulence. The performance of a telescope depends on how much light gathering capability it has, the more light it can gather the better you will see, and this is aperture. As a general rule of thumb, once you know which of the types of telescopes is best for you, get the biggest aperture you can afford for your money.

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Melting steel with solar power

Cut your energy bills by half! Complete guide to building your own solar panels. bit.ly Clip from James May's Big Ideas where bunch of hippies burn and melt stuff with their 'solar furnace', oh and it has something to do with making petrol out of thin air.

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3 Rules of Geometrical Construction for Convex & Concave Lens

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PARABOLIC MIRROR REFLECTOR 37" SUPER STRONG

linkbee.com This is a quick view of the new acrylic parabolic mirrors we have been working on. Max temperature 2700F, short focal length 9" with a 46" surface area and 95% true mirror. This is not reflective stuff, near perfect mirror.

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Concave mirror formula (By - al tahir public high school khushab) part 4

This video tutorial is about how an image of an object placed in front of a concave mirror is formed? The ray from the object fall on the mirror after the reflection the ray passes from the focus and image is formed at 2F. The image is inverted. For the derivation of the equation watch the tutorial video of Algebra.

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Matter, Energy,Environment Unit Part III / VI Download Powerpoint at www.sciencepowerpoint.com

This is Part III / VI of an educational unit that covers Matter, Energy, and the Environment. The Powerpoint version of this video and entire unit can be downloaded at sciencepowerpoint.com The Matter, Energy and Environment Unit is an educational unit for students in grades 7-10 and includes an interactive and engaging Powerpoint roadmap of 2200+ slides with built in class notes (Red Slides), lab activities, project ideas, discussion questions, assessments, challenge questions with answers, review games, videos, and much more. Text is provided in large print (32 font) and is placed at the top of each slide so it can seen and read from all angles of a classroom. A shade technique and color coded text helps to increase student focus and allows teacher to control the pace of the lesson. Also included is a 14 page (Microsoft 2003 word doc.) assessment / bundled homework package that chronologically follows the Powerpoint slideshow for nightly homework and the end of the unit assessment, as well as a 8 page modified assessment. 20 pages of class notes (Word doc.) with images are also included for students who require assistance, as well as answer keys to both of the assessments for support professionals, teachers, and homeschool parents. 28 video shorts (FLV files) are provided and a slide within the slideshow cues teacher / parent when the videos are most relevant to play. Video shorts usually range from 2-7 minutes and are included in organized folders. Two Powerpoint ...

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Myopia or Short Sightedness

•Check us out at www.tutorvista.com Myopia (Greek: μυωπία, muōpia, "nearsightedness"), is a refractive defect of the eye in which collimated light produces image focus in front of the retina when accommodation is relaxed. Those with myopia see near objects clearly but far away objects appear blurred. With myopia, the eyeball is too long, or the cornea is too steep, so images are focused in the vitreous inside the eye rather than on the retina at the back of the eye. The opposite defect of myopia is hyperopia or "farsightedness" or "long-sightedness"—this is where the cornea is too flat or the eye is too small. Mainstream eye care professionals most commonly correct myopia through the use of corrective lenses, such as glasses or contact lenses. It may also be corrected by refractive surgery, but this does have many risks and side effects. The corrective lenses have a negative optical power (ie are concave) which compensates for the excessive positive diopters of the myopic eye. The Mainstream view on correction is countered by alternative theories of cause and therefore correction. The main alternative theory claims that myopia is caused by excessive near sight work. This causes the focusing muscle inside the eye to lock up into a state of near focus. Therefore the correction of myopia would be through less close work and helping the eye to do close work with the use of reading glasses

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1960s Vicke Lindstrand vase with ground lenses and purple-black spots

www.modernistglass.com Here's our view on Lindstrand: we think his work at Kosta from 1950 to 1973 is the finest body of work, in terms of range and overall beauty, by any single mid-century glass designer. We also think it's underrated and destined to rise in price even more than other mid-century art glass (which is generally a bargain compared to new art glass anyway). This piece, mixing seemingly random ellipses of purple and concave cut lenses in a heavy, high quality crystal vase, is yet another fine example of his work. Height: 21 cm (8.25 inches) Width: 9 cm (oval shape) Weight: 2265 g Engraved "Kosta LS 605" to the base Condition: very light wear to the base, a 2.8cm long scuffmark on the side, a shallow 1mm fleck to one of the cut lenses, a couple of fairly light scratches inside (longest 3 cm) Our Reference: 2530 Pricing information Price: US $780.00 + shipping

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A 17-85 Lens on a Canon HFS10, go Fish-Eye

I got a plano-concave lens from a 17-85 Canon that I broke, and then have I've mounted it on a Canon camera HSF10 to try to make it a Fish-Eye

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Phoenix 1000mm f/8 Mirror Lens with Mount for Canon EOS 30D 20D 5D Digital Rebel XT XTI & Film SLR Cameras

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Date Created :
Nov 01, 2010 11:17:08

Kit includes:
♦ 1) Phoenix 500mm f/8 Mirror Lens
♦ 2) Phoenix 2x Teleconverter
♦ 3) Precision Design T-Mount for Canon EOS (Autofocus)
♦ 4) Rear Lens Cap

Phoenix 500mm f/8 Mirror Lens includes: Filter Set (ND-2X, ND-4X, Skylight); Soft Pouch; Front and Rear Caps; Instruction Manual; Phoenix USA Warranty

This super-telephoto 500mm mirror lens and 2x teleconverter are incredibly compact and lightweight. Using multi-coated optics and an advanced reflex design, they're ideally suited for wildlife, nature and sports photography. The included 2x teleconverter will double the focal length to 1000mm, equivalent to the magnification a 20x high-power binocular and for additional control, a set of 3 filters (Skylight, ND-2X and ND-4X) are also supplied. Macro focusing capability provides an image to subject ratio of 1:2.7 and with the 2X teleconverter, incredibly detailed, almost life-size (1:1.35) images can be obtained. Designed to be easy to use, hold and transport, this super-telephoto lens kit offers incredible magnification and value.

Will mount to ANY Canon EOS AutoFocus Film or Canon Digital SLR Camera Including: Rebel X, Rebel XS, Rebel G, Rebel GII, Rebel 2000, Rebel Ti, Rebel T2, Rebel K2, Rebel S, Elan 7, Elan 7E, Elan 7n, Elan 7ne, EOS 1V, EOS 3, EOS 1Ds Mark II III, EOS 1D Mark II III, 10D, 20D, 30D, 40D, 5D, Digital Rebel (300D), Digital Rebel XT (350D), Digital Rebel XTi (400D), & Digital Rebel XSi (450D), Rebel XS (1000D) etc.

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This is a catadioptric lens. That means that it is very similar to a reflex, or mirror, telescope, and that it mixes mirror elements with refractive elements. The light comes in the front of the lens, goes right to the back of the lens, where it hits a large (full lens circumference) concave mirror, which then focuses all that light more tightly back in the direction it came. In the middle of the business end of the lens is another mirror, which then sends the light down the center of the lens back toward the camera, where standard refractive optical elements further magnify and focus the incoming light prior to hitting the film or sensor. A lens of this type is not only similar to a reflector telescope, it can actually perform as one, and you can find eyepiece attachments for just that purpose.

One of the significant benefits of a catadioptric lens is that you get less chromatic aberration, and so with subjects like the moon, which you expect to be grey, you actually get a grey image. With a standard refractor telephoto, you're quite likely to get colored fringes on sharp bright/dark boundaries - this is an area where reflectors can and do excel, and this lens is no exception.

Here's why: Light bends when it crosses the boundary between materials of two different densities. With normal lenses, light goes from air, into the material of the lens, and back into the air. So it bends twice. But light of differing colors bends slightly differently, and so the more bending (also known as refraction) goes on, the more likely you are to see colored edges - typically at the blue or red end of the spectrum - or even both. But a reflector system is made with mirrored surfaces, and light doesn't enter these mirrors, it just bounces right off the mirror surface, and it bounces at the same angle no matter what color it is - hence, there is no difference in the path light of various colors follows. This is why a well made reflector system doesn't present chromatic aberration, or CA, which is just a fancy term for what I just described to you.

Something else to keep in mind is that the background blur, or bokeh, of a catadioptric lens is donut shaped, instead of spherical - this is because of the light blockage at the center of the lens by the second mirror. That in turn means that you won't be shooting many images with creative depth of field with this lens; either the subject matter is in focus and the rest, if anything, irrelevant to the shot, or you probably won't be happy. Shooting distant things with no foreground like the sky or scenery on the skyline? No problem. Try a portrait with out-of-focus point light sources... ouch. Donuts! Just a word to the wise.

This particular lens has a screw type fitting that is not, by itself, compatible with the Canon mount. Consequently, there is a screw-to-Canon adapter supplied as part of this kit as well.

The lens sports a 500mm focal length, so you're looking at about a 10x magnification at the rated f/8 fixed aperture. But the kit comes with a physically separate 2x magnification element, which effectively increases the focal length to 1000mm and about 20x magnification, although of course this cuts the amount of light considerably, raising the lens' effective f-stop and requiring either a slower shutter speed or a higher ASA to get the same relative exposure for any given scene.

You don't have to use the 2x adapter; you can attach the screw-to-Canon adapter directly to the Phoenix lens and use it as 500mm, f/8. The only downside to this is that it takes a physical act to change from one mode to the other, one that exposes both the camera and the lens to dust and other environmental gremlins. As the focal length is fixed, I strongly suggest you think carefully about what you're going to shoot before you shoot it so that you don't have to fool with switching the 2x adapter in and out in the field.

The quality of the 2x adapter - or at least, lets say the quality of photos taken with the 2x adapter attached to the Phoenix - is, in my opinion, unsatisfactory for any use. The Phoenix by itself seems fine, so I think we can safely point the finger at the 2x adapter.

The lens is manual focus, focusing is smooth and positive, which was a relief to me after purchasing a much more expensive lens (0) recently and running into some unexpected and entirely unwelcome backlash problems. The focusing ring is broad and well textured, providing a positive grip that you'll be thankful for when you're trying to get that last little bit of focus accuracy. The Phoenix is a very, very sharp lens for the money and the focal length; when you get the focus exactly right, I think you'll be delighted with the degree of telescopic detail achieved. I know I am.

Although you do have to stand off from your subject a bit, this lens can also serve as a perfectly reasonable macro lens. With the 2x adapter, you can get 1.35 macro shots on a film camera, and with a digital camera that uses a c-size sensor, you add an additional 1.5x so you're really getting close to a 1:1 full macro at that point. Again, here is an area where the catadioptric lens ability to basically do away with chromatic aberration serves to get you a considerably better image overall, and the lens' overall sharpness contributes a lot (as long as the object has a very flat focal plane, of course.)

There is visible, though not particularly offensive, vignetting that occurs around the center of the image. Sometimes this can work for you; so much so that it is a common effect you can add in many image processing packages. But there are times you won't want it, and with this lens, that means using post-processing to remove it, not impossible, but not trivial, either.

The lens is moderately heavy at 360 grams (12.7 oz), and with the approximate one and half inch 2x doubling tube attached, it sticks out pretty far so there's some leverage working on you along with the weight. It isn't so much that a standard tripod is overwhelmed, but if you're going to be shooting hand-held (presumably with a lot of light!) this thing will get your wrists tired in short order, no question about it.

One thing about any fixed f-stop lens, and this lens being no exception, is that the depth of field is limited. There isn't much you can do about it. For instance, at a distance of 12 feet, the DOF of this lens is about 1/4 inch. This has a number of consequences. The obvious one is the type of subject matter you will want to shoot with this lens will be limited to that which has a relatively shallow depth of field compared to the distance you'll be shooting at. Another, perhaps not immediately obvious consequence is that focus adjustment requires you to take great care or you'll find the focal plane is not collinear with your subject matter. In my case, I'm using the lens with a Canon EOS 40D, which provides for a live LCD view which can zoom the FOV in for a 1:1 pixel (LCD:Sensor) view; this allows me to see precisely how well I'm focused (or not.) In this sense, this lens is very well-suited to my camera (or vice versa.) If you are limited to a TTL viewfinder, you may find that focusing this lens perfectly is quite challenging. The lack of backlash helps, but even so, a very slight rotation of the focusing ring does move the focal plane a considerable distance. No question about it, this is one of the tricky areas for this type of lens.

As a manual focus lens and a fixed f-stop lens, it doesn't really tell the camera anything about itself. Your aperture readout will probably show a clueless 0.0 value; don't worry about it too much. If you set the camera to aperture priority, the camera will set the shutter speed appropriately and you'll get a properly exposed image. Or you can use full manual and tweak till you find what you're looking for. Given that shutter speed affects the blur of motion in an image as well as the available exposure time, and ASA (if your camera provides for adjustable ASA) affects the exposure time and the graininess and noise of the image, it may take some experimentation before you find the optimum combination of ASA and shutter speed that works best for your particular camera. Modern digital cameras have such large megapixel counts that in many cases, you can reduce noise after the fact by trading in some resolution; for instance, if you have a 10 mp camera like my EOS 40D, you can cut the resolution by half in both dimensions (proportionally) and this results in the light values of four adjacent pixels being combined into one new one in a final 2.5 mp image, which will serve to average out a great deal of sensor noise - at the cost of some detail, of course. In the case of a not perfectly focused image, though, which I think you'll find you take quite often with this lens because the DOF is so limited, there is little down side to such a reduction in pixel dimensions - and remember, noise occurs in an image regardless of focus because it comes from the sensor, not the image.

The kit comes with several filters which need to be mounted internally; they're more for film cameras which have fewer options for easily managing light (for instance, they can't adjust ASA without actually changing a film cannister.) They're quite inconvenient as they mount inside the lens at the adapter end, and so I have not even tried to use them. Nor do I really see a huge need for them in my situation. The only exception is related to the fact that filters can increase contrast as they block out ranges of light which may be obliterating certain features by virtue (or lack thereof) its abundance. So your mileage may vary; the filters are there if you choose to use them.

Last but not least, the lens comes with all the caps you need to keep dust off it, as well as a handy soft bag you can use to protect the fine surface features. It's a typical soft bag and it won't serve to protect the lens if, for instance, you were so unfortunate as to drop it. For that, you need a camera bag. As with all lenses, this baby is delicate, and the very first thing you should invest in is a bag that will keep the slings and arrows of outrageous fortune from lodging in your lens collection.

In summary, there can be no question that this is a special purpose lens, but when you are shooting distant objects on the ground or in the sky, it really comes into its own. It is all metal, at least on the outside, and feels very solid and frankly, it also feels expensive. Given the price, which is more than reasonable, and the build quality, which in my opinion is quite high, I think almost anyone who likes to really experiment with different types of images should have this lens in their kit bag. I recommend it enthusiastically and with great cheer. I'm very happy to have it myself, and I'd immediately and without any question replace it with the same model if something unfortunate happened to mine.

You can't put 500mm of telephoto capability in your camera bag at anywhere near this price point using standard lens designs; if you are willing to put out more money, you can get a better result, no question about it, but this is still a terrific way to start with telephoto photography.

In the next few days and evenings, I'm going to prepare some sample images taken with this lens specifically to go along with this review; please check the images section if you'd like to see them.

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Internal Anatomy of Hurricane/Vortex NASA Satellite

Concentrated spheres, such as Earth are surrounded by layers of light of equal pressures. Clouds float around the Earth in them. The reason they float in curves parallel to the Earth is because of these spherical equipotential planes of pressures which curve as the Earth curves. Curved pressures of light act as lenses to multiply and divide light radially. (Spiraling) Light rays which pass through curved planes concentrate to a point when projected through light lenses of space in the convex direction and decentrate when they pass through the concave direction --------------------------------------------------------------------- Vector Fields and Hydrodynamics Force fields have definite properties of their own suitable for scientific study. Produced by the California Institute of Technology 1985. video.google.com --------------------------------------------------------------------- Kepler to Einstein From Kepler's laws and the theory of tides, to Einstein's general theory of relativity, into black holes, and beyond. Produced by the California Institute of Technology 1985. video.google.com --------------------------------------------------------------------- Overall,Tesla States that the sun acts as a "generator" for our solar system. It emits enormous amounts of radiation, which Tesla called "primary solar rays" (and lead to modern concept of cosmic rays). These rays in turn, hit various particles in space which give rise to much weaker secondary radiations. The primary ...

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The Right Way to Wear Contact Lenses

People who are used to wearing spectacles often have a hard time adjusting to contact lenses. It may take weeks before one becomes completely comfortable with lenses. To make sure that you are wearing your contact lens the right way, follow these tips:

Place the lens on your finger tip and let the lens form a natural concave. Look at the lens from the side. It should form what seems like a perfect curve, like half of a ball. If the edges of the lens flares out slightly then it is inverted. Some lenses also come with a handling tint and you'll know if it's the right side if the tint is clear when you look down on it on your finger tips. Wearing your contact lens can be extremely uncomfortable but it will not really cause any damage to your eyesight.

Before putting on or taking your lenses off, make sure your hands are clean so as not to contaminate them with any harmful germs or dirt. Do not use hand cleansers that contain lanolin or too much moisturizers. They will damage your contact lenses or can irritate your eyes. Use your other hand to open the lid of your eyes. Look up or down when placing your contact lenses and then roll your eyes to get it in the right place. Blink and let your eyes get comfortable with the lenses.

Always clean your lenses with the appropriate solution. You may damage not just your lenses but also your eyes when you use inappropriate liquids to clean out the contact lens. Make sure to get enough cleaning solutions for your lenses. When you are just taking out your lenses from the case, slowly slide it to the palm of your hand from the case. Do not pull them out if they stick on the floor or the sides of the case to avoid tearing them.

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Canon EF 180mm f3.5L Macro USM AutoFocus Telephoto Lens for Canon SLR Cameras

Buy Canon EF 180mm f3.5L Macro USM AutoFocus Telephoto Lens for Canon SLR Cameras Order Today!

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A telephoto macro lens with a maximum magnification of 1x. Life-size close-ups can be taken from a farther distance without disturbing the subject (insects, etc.). The internal floating system minimizes fluctuations in aberrations caused by changes in the focusing distance. Optical performance is outstanding from 1x to infinity.

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Over the years I have owned both Canon's 50mm and 100mm Macro, they are excellent lens and substantially less expensive. If you want to shoot insects and other small, shy creatures outdoors the 180 mm Macro is the lens to get.

Optically the lens is excellent in every way. The 'slow' focus is a function of the huge focal range of the lens, typically manual focus is used for macro photography - for general photography the focus limiter can be used to improve focus time. Construction quality is excellent - although the included lens hood is a rather cheap plastic design, however it functions fine.

I use this lens on a tripod almost all the time - with Macro work you are normally are working a smaller apertures (f8-f16), so relatively slow shutter speeds are the norm - the tripod ring makes transitioning from portrait to landscape very easy.

Additionally this quality of this lens allows the use of canons 1.4x teleconverter with minimal loss of quality - significantly increasing the 'reach' of this lens.

This lens is a good general purpose 'short' telephoto - but not suitable for sports or action photography, Canon's EF 70-200 lenses or 200mm f2.8 lens make better alternatives.

Image stabilization is not available for this lens and would make a very useful addition

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ICE LED 6mm Pitch Video The Perfect large format video wall

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WATER BEAR in NEW YORK CITY!

YEAH! Finally found my first tardigrade " WATER BEAR" on green lichen on elm. I squeezed it's water onto concave slide and shot this footage on my Celestron Digital microscope at 40x objective lens.

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A look at ray tracing for diverging (concave) lenses.

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Hubble's View Of The Universe [Part 6]

Hubble's View Of The Universe [Part 6 of 10] THE HUBBLE TELESCOPE Hubble works on the same principle as the first reflecting telescope built in the 1600s by Isaac Newton. Light enters the telescope and strikes a concave primary mirror, which acts like a lens to focus the light. The bigger the mirror, the better the image. In Hubble, light from the primary mirror is reflected to a smaller secondary mirror in front of the primary mirror, then back through a hole in the primary to instruments clustered behind the focal plane (where the image is in focus). THE UNIVERSE Hubble's longest exposures are like a core sample of the universe, recording galaxies at many different distances. This is one of the deepest core samples ever taken. It shows a few nearby stars in our Milky Way galaxy. The rest of the objects are distant galaxies, extending from 1 billion to over 10 billion light-years away. STARS Stars live and die over the course of millions to billions of years. It is unusual to see changes in individual stars. To learn more about them, we must piece together snapshots of stars at different life stages — from birth to death. The birth, life, and rebirth of stars is an ongoing process in the universe. The byproducts of this process include planets and the elements that make life possible. GALAXIES Galaxies come in diverse shapes and sizes. NGC 4414 — which is located about 62 million light-years away — is an example of a spiral galaxy. As with most spirals, the central ...

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Physics: Angle of Incidence

Watch more free lectures and examples of Physics at www.educator.com Other subjects include Algebra, Trigonometry, Calculus, Biology, Chemistry, Statistics, and Computer Science. -All lectures are broken down by individual topics -No more wasted time -Just search and jump directly to the answer

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Physics: optics of lenses and mirrors (11)

Physics: Introduction to the optics of lenses and mirrors. Concave, convex, converging, diverging; real, virtual; upright, inverted, magnified, shrunk. Sign conventions for focal length, image distance, object distance, magnification. The lens/mirror equation; the magnification equation. Introduction to ray tracing. This is arecording of a tutoring session, posted with the student's permission. These videos are offered on a "pay-what-you-like" basis. You can pay for the use of the videos at my website: www.freelance-teacher.com For printable documents containing the "handout" and problems discussed in this video series, go to my website. For a list of all the available video series, arranged in suggested viewing order, go to my website. For a playlist containing all the videos in this series, click here: www.youtube.com (1) The lens/mirror equation. Focal length distance, object distance. Convex, concave, diverging, converging (2) Image distance. Real, virtual (3) Continued (4) Continued. Upright, inverted (5) Continued. Magnification equation (6) Continued. The lens/mirror chart (7) A problem (8) Continued. Ray tracing (9) Continued (10) Another problem (11) Continued

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PARABOLIC MIRROR SOLAR COLLECTOR SQUARE PARABOLOID FREE GREEN ENERGY

www.greenpowerscience.com This is a large fiberglass parabolic shape made out of fiberglass. It is very powerful and has the part A mirror 80%. I will be adding the Part B to jack it up to 95%. The focal point is longer and takes a bit getting used to, especially getting in the habit of walking behind the parabolic mirror:-)

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Primary Forces of the Earth System Explained by NASA

Concentrated spheres, such as Earth, are surrounded by layers of light of equal pressures. Clouds float around the Earth in them. The reason they float in curves parallel to the Earth is because of these spherical equipotential planes of pressures which curve as the Earth curves. Curved pressures of light act as lenses to multiply and divide light radially. (Spiraling) Light rays which pass through curved planes concentrate to a point when projected through light lenses of space in the convex direction and decentrate when they pass through the concave direction --------------------------------------------------------------------- Harmony of the Spheres A last lingering look back at mechanics to see new connections between old discoveries. Produced by the California Institute of Technology 1985 video.google.com --------------------------------------------------------------------- Vector Fields and Hydrodynamics Force fields have definite properties of their own suitable for scientific study. Produced by the California Institute of Technology 1985. video.google.com --------------------------------------------------------------------- Kepler to Einstein From Kepler's laws and the theory of tides, to Einstein's general theory of relativity, into black holes, and beyond. Produced by the California Institute of Technology 1985. video.google.com --------------------------------------------------------------------- Overall,Tesla States that the sun acts as a "generator" for our ...

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dying brine shrimp

Shot on Celestron Digital Microscope 40x objective lens day two after being applied to concave slide

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burning paper with a convex lens

What happens to paper when it is exposed to paper through a convex lens?

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Physics: optics of lenses and mirrors (4)

Physics: Introduction to the optics of lenses and mirrors. Concave, convex, converging, diverging; real, virtual; upright, inverted, magnified, shrunk. Sign conventions for focal length, image distance, object distance, magnification. The lens/mirror equation; the magnification equation. Introduction to ray tracing. This is arecording of a tutoring session, posted with the student's permission. These videos are offered on a "pay-what-you-like" basis. You can pay for the use of the videos at my website: www.freelance-teacher.com For printable documents containing the "handout" and problems discussed in this video series, go to my website. For a list of all the available video series, arranged in suggested viewing order, go to my website. For a playlist containing all the videos in this series, click here: www.youtube.com (1) The lens/mirror equation. Focal length distance, object distance. Convex, concave, diverging, converging (2) Image distance. Real, virtual (3) Continued. Magnified, shrunk (4) Continued. Upright, inverted (5) Continued. Magnification equation (6) Continued. The lens/mirror chart (7) A problem (8) Continued. Ray tracing (9) Continued (10) Another problem (11) Continued

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Physics: optics of lenses and mirrors (1)

Physics: Introduction to geometric optics for lenses and mirrors. Concave, convex, converging, diverging; real, virtual; upright, inverted, magnified, shrunk. Sign conventions for focal length, image distance, object distance, magnification. The lens/mirror equation; the magnification equation. Introduction to ray tracing. This is arecording of a tutoring session, posted with the student's permission. These videos are offered on a "pay-what-you-like" basis. You can pay for the use of the videos at my website: www.freelance-teacher.com For printable documents containing the "handout" and problems discussed in this video series, go to my website. For a list of all the available video series, arranged in suggested viewing order, go to my website. For a playlist containing all the videos in this series, click here: www.youtube.com (1) The lens/mirror equation. Focal length distance, object distance. Convex, concave, diverging, converging (2) Image distance. Real, virtual (3) Continued. Magnified, shrunk (4) Continued. Upright, inverted (5) Continued. Magnification equation (6) Continued. The lens/mirror chart (7) A problem (8) Continued. Ray tracing (9) Continued (10) Another problem (11) Continued tags: educational college student MCAT exam instructional video

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5 Great Tips On Buying A Telescope

Aiming a telescope at the night sky has been one of my hobbies for quite a few years. Ever since I was a kid I spent many evenings gazing up into the Milky Way and wondered how many? How far away and how big must some of those stars be? As I got older and my interest in astronomy persisted, I decided it was time I bought a telescope. I started shopping around and found not only are there many types, but of course different features and accessories. I had no idea there were so many choices.

If this is your first telescope, the choices can be overwhelming so I've included suggestions and some of the questions you may want to ask telescope dealers and yourself before you actually buy your first scope. If you already own a scope, these tips will still come in handy if you're thinking a buying a new one.

- First, think of the reasons you want a telescope. Are you part of a stargazing club or planning on joining one? Has it been a passion since childhood? Do you plan on giving it as a gift to a budding young astronomer? Maybe you want to catch a glimpse of the space station as it darts across the night sky! If you plan to get a lot of use from your telescope, the best bet is to buy a larger scope with more features. You'll want one that doesn't limit your ability to explore the heavens. The better the quality, the more you'll enjoy the experience and further your interest. If, on the other hand, you've just read the paper and found out there's going to be a lunar eclipse this weekend, a smaller scope with less features is the way to go. You won't want to lay out big bucks for a great telescope with all the bells and whistles for something you'll get only occasional use from.

Bend, Bounce Or Both?

- What kind of Telescope should you get? The 3 types are refractor, reflector and compound, or catadioptric.

A refractor telescope collects light at the top of a long, slender tube and bends or concentrates it to an eyepiece at the bottom. It's popular with observers whose main interest is the Moon and planets within our own solar system. They provide sharp, high-contrast views at higher magnifications and are less bothered by atmospheric disturbance and than the reflector or compound types. Because of this it makes an excellent choice for observation in a city setting.

The reflector telescope uses a concave mirror at the bottom of a tube, rather than a lens at the top, to gather and focus light. Newtonian reflectors, the most common design, reflect (bounce) the collected light to a smaller secondary mirror at the top end directing the focused light to an eyepiece on the side of the tube, making for a comfortable upright viewing position. These scopes are perfect for those living in an urban or country setting and who wish to explore deeper into the cosmos. They are usually larger and a little bulky in size making transport more difficult.

The third type, a catadioptric, employs a combination of lenses and mirrors to gather and focus light. Its design allows for a larger aperture mirror in a smaller space. Like the Newtonian, light is collected by a mirror in the bottom of the scope. Unlike the Newtonian, the tube is much shorter, making handling and transport easier. The light reflects off the back mirror to a secondary mirror near the top of the scope where it's concentrated once again and reflected to the eyepiece in the bottom of the tube. This design is also excellent for viewing objects beyond our neighbor planets.

Location, Location, Location

- It's true in real estate and it's true in astronomy. If you live in a city where there's well lit streets and neon signs flashing brightly at night, you may need to travel to areas away from the glow. It seriously hampers any attempt at stargazing. If you need to travel any distance to find a good location to practice your hobby, you'll want a telescope that's easy to set up and take down. Don't buy a scope that never comes out of the box because it's too much of a hassle to put together. A place in the suburbs or even the countryside is a much more inviting location. A quiet, peaceful setting with no streetlights, preferably with some elevation is perfect for viewing very faint objects in deep space. Buy a scope with a large objective lense (the larger the objective lens the more light gathering capability it has) and point it to almost any location in the Milky Way and you're sure to be thrilled by what you see.

Hobby Or Passion?

- Are you going out every weekend to observe stars and planets? Do you use star charts and plot locations of various constellations? Do you research deep space objects on the internet? Do you use a CCD (charged coupled device) Camera for astrophotography? If so, then you probably already have an impressive telescope and just want to upgrade and purchase a new scope or accessory. Again the objective lens of your new telescope is an important factor when deciding. You want to gather as much light as possible to provide lots of detail in your photos.

You may just want to take the your new scope on a camping trip with the family. In that case a smaller scope or even binoculars would be particularly well suited for that purpose. It's easy to pack, set up and take down, and very portable. Don't buy the biggest baddest telescope on the market, you'll never fit it in a backpack!

- Lastly, the price you're willing to pay for a new scope will ultimately determine the type of scope you buy as well as the size. You can spend a couple hundred dollars for a simple high quality scope if you're just starting out. Or you can spend thousands for a larger scope with more accessories than a New York model. Your answers to the questions above and your own good judgement will provide you with a firm platform to make a quality decision. If you're solidly entrenched in astronomy and the related fields, astrophotography, star charting etc. then you already have a good idea on the kind of scope you want. If this is your first telescope, I hope these suggestions and ideas have helped. Good luck and have fun stargazing!

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Focal Length of Convex Lenses

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