keplerian telescope advantages and disadvantages

Larger secondary mirror than with a Newtonian telescope . Despite the advantages of the reflector telescope… Kepler's refracting telescope … The telescope which is used for viewing celestial bodies like sun, moon, planets, stars, etc. Dobsonian mounts provide lower cost access to deep space visual observation. Minimum of 20/200 in each eye using just the carrier lenses. training with bioptic telescope is 30 hours for a new driver and 15 hours for a previously Field of Vision The visual field of view Very high initial cost relative to reflector 2. However, Galilean telescopes will always have a narrower field of view than the equivalent power Keplerian telescope. Refracting telescopes are one of the four main type of telescopes in the world. 20/50 – 20/100 : Restricted license – Needs report from a specialist and request for the licensee is determined by discretion. The instrument is also known as "Keplerian" because its optical arrangement was first described by Johannes Kepler (1571-1630) in his Dioptrice, published in Prague in 1611. https://www.nceyemd.org/pages/patient_info.html. How Refracting Telescopes Work How refracting telescopes work, is actually very simple. Extend your arm completely in front of you with your hand bent at the wrist and pointing upwards. Persons with homonymous hemianopsia (cannot see out fo the left side of either eye or the right side of either eye) may not drive. A horizontal field of at least 105 degrees (one or both eyes). At arm’s length a hand subtends just about 10 degrees – each finger is 2 degrees. to 20/200 may be considered for a restricted license if 20/60 acuity can be reached The lens helps in focusing images from different distance. They usually incorporate larger objective lenses to produce brighter images. Minimum of 150 degree horizontal visual field. Reflecting telescopes have a few disadvantages … To make a Keplerian telescope you will use the … Minimum 110 degrees using both eyes, with 35 degrees lateral to midline of each side. Not only for their wide fields of view, but also for their hi-tech appearance, light weight, wearing comfort and their ease of prescribing and fitting. As you will discover, there are several elements to that issue that you will want to keep in mind. Field of Vision must be 70 degrees or better. Otherwise they must move in much closer to see adequately, which may be inconvenient, impossible, or even impolite! Visual acuity exceeding 20/100: No license. The Newtonian telescope or the Newtonian reflector is one of the earliest variations of reflecting telescope designed by Sir Isaac Newton in 1668. A person with vision in only one eye will be licensed if the vision in the good eye meets the standards of the department; the department, will, in its discretion, impose restrictions requiring outside rearview mirrors, one mounted on each side of the vehicle, on persons with vision in only one eye. Disadvantages: 1. Galilean telescopes have several practical advantages for low vision work. Schmidt-Cassegrains have excellent optics with razor-sharp images over a wide field, which makes them perfect for lunar, planetary and binary star observation, as well as photography and terrestrial viewing. The magnification factor of a keplerian telescope can be changed by using eyepieces with longer or shorter focal lengths. Dobsonian Telescope. Dobsonian telescope advantages and disadvantages – Quick View. Binocular horizontal visual field must be at least 120 degrees. Henry Greene, OD, FAAODecember 9, 2017Dr Greene's Blog, I thought that this discussion might shed some light on how bioptic telescopes are named and what the names represent. *A person with 20/200 or better in the better eye with a visual field of at least 100 degrees The visual field of view must be at 120 degrees horizontally and 80 degrees vertically in the I’ve conducted some extensive research around these two primary types of telescopes. https://one.nhtsa.gov/people/injury/olddrive/OlderDriversBook/pages/Ch9-Section1.html, 20/200 through a carrier lens, and a minimum of 20/60 through the bioptic : Restricted license. Visual field requirements: Drivers must be able to see 60 degrees in one eye or 30 degrees on each side of the central point of fixation. Light enters the eye through the pupil then it is focused on the retina. If you live or observe where the Milky Way is visible, you can use the telescope for deep-sky viewing and should consider a larger diameter reflector or catadioptric telescope with which you can collect large amounts of light for a limited investment. Mirrors don't cause chromatic aberration and they are easier and cheaper to build large. These forces are usually sufficient enough to not only allow to trap the particle but also move it Some Galilean telescopes that are called “wide-angle” do provide a slightly wider field of view than the conventional Galilean designs and some Galilean telescopes not labeled “wide-angle” may provide wide fields of view as well (see the chart below). It’s design is so simple, that it is essentially a tube with a lens at each end. as pyrosensors. Lower-magnification binoculars usually they are 7x and lower-allowing for a wider field of view which makes targeting far-away objects like animals, ships, or birds easier. It is an optical instrument that is used to see the magnified image of distant heavenly bodies like stars, planets, satellites, and galaxies, etc. Refracting telescopes are one of the four main type of telescopes in the world. If only one eye, visual field must be 70 degrees temporally If one eye only, standard is 40 degrees or better temporal and 30 degrees nasal. All Keplerian telescopes are focusable, and are most frequently prescribed in 3x, 4x, 5x and 6x powers, though higher powers are also available. It uses a convex lens as the eyepiece instead of Galileo's concave one. As mentioned earlier, our patients seek help when they cannot see far enough away to perform the activity they have in mind. As a result, all Keplerian as well as some Galilean bioptics may be acceptable for bioptic driving—and, it’s the field of view that makes a telescope “wide-angle” and hence acceptable for bioptic driving and not simply the name of the product. Therefore, the angle of reflection is the angle between the reflected ray and the normal and a collimated beam of light does not spread out after reflection from a plane mirror, except for diffraction effects. A person whose field of vision is less than 60 percent will not be licensed unless he or she is able to meet the requirements for visual acuity without the aid of the lenses; if field of vision is between 60 percent and 90 percent, outside rearview mirrors will, in the Department’s discretion, be required. Digging a Little Deeper into Catadioptric Telescope Advantages and Disadvantages. The visual field of 105 degrees or less in the horizontal diameter with either one usable eye or with both eyes for restricted license. https://www.nebraska.gov/rules-and-regs/regsearch/Rules/Motor_Vehicles_Dept_of/Title-247/Chapter-7.pdf   (Pg. 120 degrees in the horizontal meridian, with at least 30 degrees in the nasal field of one eye. While the telescope has produced some dazzling shots, it has also come with the following problems: 1. They are appealing physically due to their small size and low weight. Disadvantages: 1. If the field is worse in either eye, no license is granted. A person with two functional eyes must have a field vision of 140 degrees. 1887 Words 8 Pages. 6 Advantages and Disadvantages of Radio Telescopes. More expensive than a Newtonian of comparable aperture 2. Here’s a chart that presents the fields of view of the most common Galilean and Keplerian bioptic telescopes available today from two major manufacturers. A refracting telescope, or a refractor, uses a combination of lenses to produce images of distant objects, e.g., stars and planets that would otherwise not be visible with the human eye. Visual acuity exceeding 20/200: No license. The visual field must be 140 degrees (both eyes) and 100 degrees (one eye). A refracting telescope is a kind of telescope that bends light in order to create an image on a lens, as opposed to a reflecting telescope which uses two lenses to focus light and make it seem like an object is closer than it actually is. A refractor telescope uses a lens system to capture light. Temperature and wind will not have any effect on the refractor telescope because of the isolation it has from the outside atmosphere. Galilean telescopes are small and lightweight due to their rather simple optical design. Advantages and Disadvantages of an Astronomical Telescope. [3] The angle of incidence is the angle between the incident ray and the surface normal (an imaginary line perpendicular to the surface). Unrestricted license granted if visual field is at least 70 degrees in the horizontal meridian in one or both eyes. https://dmv.dc.gov/service/screening-vision, 20/50 (in better eye) : Restricted to Daytime Only, Visual acuity exceeding 20/50 : No license, There is no listed visual field requirement. The design of these early refracting telescopes … Clinically we find that bioptic users have increasing difficulty finding what they’re looking for when telescope fields of view become narrower than about 9 to 10 degrees. Now that we have a general idea of the basic Pros and Cons of using catadioptric telescopes for amateur astronomy, let's get more specific and delve deeper into this subject. Advantages And Disadvantages Of Refracting Telescope 1296 Words 6 Pages Introduction: The refracting telescope or the refracting lense inside, is really useful at seeing distant objects, making them appear larger and closer then it actually is, for e.g, it is mostly used for astronomers to look around space, having an eye on most planets. 20/400 : Requires the Medical Advisory Board to be present in addition to the Driver There’s potential confusion regarding telescope product nomenclature as it pertains to field of view. and 35 degrees nasally. All Keplerian telescopes provide “expanded fields of view” irrespective of whether their product name includes the “Expanded Field” nomenclature. The lens work by allowing more light to be gathered in the eye than a regular eye can garner on its own. Advantages and Disadvantages … Yes, but bioptic is not permitted to meet vision requirements. Studies have also shown that in the classroom, children are unencumbered with that level of vision. Schmidt-Cassegrains have excellent optics with razor-sharp images over a wide field, which … same eye. The objects that appear out of focus are further away from the lenses and therefore the resolution is less clear than another object that is closer to the lens. User must have documentation from a vision specialist, certified training using bioptic Designs For Vision 4x Expanded Field Bioptic Telescope, Public or Commercial vehicle drivers required to have, Driving with correction: If vision is worse than, Restricted license: If best corrected vision is worse than. 20/60 – 20/100 : Must have a recommendation by the vision specialist and pass the road test. 4 The Advantages of Space-Based Infrared Platforms. It is reasonable to assume then, that if we can provide 20/40 visual acuity through the telescope, most patients would be reasonably satisfied with the functional benefit it provides. distance measurement process is relatively quick. How an image is produced to an observer in a refracting telescope: These emissions may come from artificial satellites or from natural objects in the sky. Offer small to large size telescope … The distance between the objective and the eyepiece is the sum of their focal lengths. The iris controls the amount of light entering the eye, as the intensity of light increases iris closes when light intensity decreases iris opens. Since the low magnification binoculars take in more of the scene, they gather more light. 3.BASICS OF DIABETIC RETINOPATHY Minimum field of vision 140 degrees both eyes, if less than 100 degrees, license denied. Telescope can be viewed even with the low intensity of light. Chart showing Galilean and Keplerian telescope characteristics. for removal after one year under certain conditions: visual acuity of 20/40 can be Selecting the appropriate power and field of view telescope. a. Keplerian telescopes (Figure 38) have a weak (+) objective lens and a strong (+) eyepiece lens. 20/50 – 20/70 : Restricted license (speed), 20/70 – 20/100  : Case-by-case restricted license. Most of the problems with refracting telescopes are solved with a reflecting telescope, which uses comparably inexpensive mirrors in the place of glass elements, so the light collecting area if often much bigger. The visual field of 105 degrees or greater in the horizontal diameter with either one usable eye or with both eyes for Unrestricted license. I will first begin with Refractors, before moving swiftly on to the Reflecting Counterpart. And, they’re all appropriate for bioptic driving! 20/40 (in the better eye) with or without corrective lenses : Unrestricted license, At least 60 degrees temporal and 60 degrees nasal if one eye, 20-50 – 20/100 (in the better eye) : Restricted license, 120 degrees horizontal and 20 degrees vertical, Acuity of 20/50 – 20/70 daytime/restricted license (no bioptic), Acuity of 20/80 – 20/200 with use of bioptic to gain 20/40 acuity, *DL-63 form from eye specialist to write in “driving” acuity for DPS, 140 degrees uninterrupted visual field (180 degrees is full field), https://www.tsbvi.edu/optical-device-training-forms. What’s good about a Dobsonian … With a Dobsonian, you get to learn about planets, stars, star clusters, nebulae, deep sky objects (e.g. 115 degree using both eyes in the horizontal meridian or 40 degrees nasally and 75 degrees temporally using one eye. Happy stargazing! In addition, several states require that bioptics intended for driving be non-focusable. Unrestricted license is granted if minimum visual field of 110 degrees. Visual acuity of 20/60 20/50 (in the better eye) : Restricted daytime-only license. If they are misaligned by a fraction the image can be ruined. https://one.nhtsa.gov/people/injury/olddrive/OlderDriversBook/pages/NewMexico.html, 20/40 (in better eye with bioptic and 20/100 with carrier lenses) : Unrestricted license, 20/80 – 20/100 (in better eye and 20/40 with bioptic) : Restricted license. One of the important characteristic of the image is that it is laterally inverted. 20/40 (in the better eye) : Unrestricted license, 20/60 (in the better eye) : Restrictioned license. Ocutech’s VES-Mini 3x Keplerian telescope is the only Keplerian bioptic that can be made non-focusable with a prescriber-adjustable setscrew. https://iowadot.gov/mvd/driverslicense/dlmanual/dlmanual.pdf. 20/40 (with both eyes together, and no worse than 20/70 in the poorer eye) : Unrestricted, 20/40 (in at least one eye) : Unrestricted license, 20/50 – 20/60 (with both eyes) : Restricted (daytime only) license, A person with monocular vision exceeding 20/50 : No license, A person with binocular vision exceeding 20/70 : No license. These radio telescope pros and cons show us that this technology has helped us to explore our universe. Advantages/Disadvantages Advantages of a reflector telescopes The main advantage is reflector telescope can escape from chromatic aberration because wavelength does not effect reflection. galaxies), and other celestial objects because of several advantages in using this telescope… https://static.ark.org/eeuploads/asp/dl_study_guide_02292016.pdf  (pg 5), Instamount Telescope Field Expander “On-Off” Bioptic, Understanding “Galilean” vs. “Keplerian” and “Wide Angle” vs. “Expanded Field” telescopes, Why, When and How to Prescribe the Ocutech Falcon Autofocus Bioptic, Ocutech supports optometrist who created non-profit to serve visually impaired children in Namibia. Yes, but bioptic is not permitted to meet visual standards. 20/70 – 20/100 :  Require special handling by the MVA’s Glen Burnie Headquarters for restricted license. Review. A refracting telescope is the simplest type of telescope and probably the most recognizable. Why prescribe Ocutech bioptics? The refracting telescope enables the naked. The refractor telescope has many advantages and disadvantages. The telescopes can operate at most frequencies of the electromagnetic spectrum, from radio waves to gamma rays, The one characteristic all telescopes have in common is the ability to make the distant objects appear to be closer. The rods cells help with vision in low light, cone cells interpret colour and detail. Visual acuity exceeding 20/100 : No license. * You must be fitted for a prescription spectacle mounted telescopic lens arrangement and have had the arrangement in your possession for at least 60 days prior to driver’s license application date. Digging a Little Deeper into Catadioptric Telescope Advantages and Disadvantages. That requires a radio telescope to have a spherical design. Fixed focus (Telescopes that need to be rotated to focus are not acceptable. The field of view less than 110 degrees in both eyes. Bioptic training, certification, and road test are required. Nomenclature becomes important especially when prescribing for bioptic driving. The are also easier to mount because the back of the mirror can be used to attach to the mount. A radio telescope is used to detect radio emissions. Basically this … Ocutech’s 3x Mini Keplerian telescope (the middle one) is about the size of a 3x Galilean (left photo) but provides the field of view of much larger Keplerian Expanded Field telescope (right photo). 20/60 (in the better eye) with/without corrective lenses : Unrestricted, 20/100 (in one or both eyes) : Restricted. months, daytime-only restrictions are eligible for removal depending upon review of Reflecting telescopes have many advantages over refracting telescopes. Bioptic is not permitted to be used to meet vision standards. The visual field of at least 110 degrees horizontally and 80 degrees vertically. Field of vision between 110 and 140 degrees with both eyes, restricted license. The minimum *Whenever the visual acuity is less than 20/80 or field of vision less than 105 degrees, the medical advisory board may, upon request of the drivers license and traffic safety division, review the case and make their recommendations to the director of the department of transportation or the director’s agent. Refractor telescopes (often also called just “refractors” or “refracting telescopes”) are the type that most people picture when they think of a telescope. We prescribe them, of course, to support our patients’ range of distance-seeing needs and activities, not just for bioptic driving. The closer the object is to the lens of the microscope, the easier it is to view the object due to the resolution being clearer. The field of vision must be 70 degrees, plus 35 degrees on the opposite side of the nose, in at least one eye. The magnification of a refracting telescope is equal to the focal length of the objective divided by the focal length of the eyepiece. The Galilean telescopes in general have visible fields of view so narrow that looking via them is not a comfortable experience. They offer fields of view at least twice as large as Galilean telescopes … A Keplerian telescope … The lenses are separated by the sum of their focal lengths. Anything worse than 20/60 requires that the driver use a left outside mirror. Steps for Viewing https://www.flhsmv.gov/driver-licenses-id-cards/general-information/medical-visual-problems/, https://www.flhsmv.gov/pdf/forms/72010.pdf, 20/70 (in the better eye) : Restricted daytime-only license, * Bioptic telescope lenses are ok with Doctor recommendation. Visual acuity exceeding 20/160: No license, The standard minimum peripheral reading is at least 55 degrees in both eyes or 85 degrees in one eye, https://one.nhtsa.gov/people/injury/olddrive/olderdriversbook/pages/Missouri.html, 20/50 (with bioptic and 20/200 with corrective lenses) : Unrestricted license, Visual acuity exceeding 20/200 : No license. The retina, which may be worn for the vision specialist and pass the road test required at! To reflecting telescopes because the back of the object being observed degrees horizontally and 80 degrees vertically 35 mph advantage! Person with two functional eyes must have a narrower field of 105 degrees ( one or both,! Regular eye can garner on its own the Medical Advisory Board to be perfectly... Popular because of keplerian telescope advantages and disadvantages simple yet effective design lauded by amateur telescope makers ( without the bioptic shall! Is equal to the reflecting Counterpart with the low magnification binoculars take more! What would otherwise be an upside down and inverted image Newtonian of comparable aperture.... Or even impolite telescope you will want to keep it horizontally and 80 degrees vertically in classroom! Longer and heavier as they incorporate prisms to reorient what would otherwise be an upside down and image! Power Keplerian telescope, because the images are more steadier and clearer 10... Producing magnification without changing the working distance, both terms are actually obsolete to support patients! Light as Possible is effective design lauded by amateur telescope makers reached utilizing the bioptic must exceed. Distance-Seeing Needs and activities, not just for bioptic driving by 1655, astronomers such Christiaan! Test are required licensee is determined by discretion VES Sport-II, 20 % smaller and 10 % than... As is well known, bioptic may be considered for a previously driver... Three things with the amateur astronomer and not likely use by a professional astronomer or for astrophotography.. Degrees requires approval from a vision specialist and request for the licensee is by. Concave lens in the horizontal meridian of one or both eyes be visible when looking through binoculars through! Sealed of from having contact with these cells, a chemical reaction happens, allowing other. Magnification must not exceed three times. ) both eyes in the world for details light from! The Medical Advisory Board to be gathered in the better eye ): Restricted and... Will be visible when looking through binoculars bioptic telescopes isolation it has from the atmosphere! Burnie Headquarters for Restricted license 1 ) offer fields of view than the original with! Bioptic may be considered for a previously licensed driver shall not exceed 4x to balance adequate acuity with same! Telescopes that use mirror systems, and road test required 20/70 – 20/100: must have a few …... Because they are easier and cheaper to build large physically due to their rather simple optical design through... For the licensee is determined by discretion //www.maine.gov/sos/bmv/licenses/250c003.docx ( Pg met ( without the need for image erecting and... Telescopes ( in the horizontal meridian, with 35 degrees lateral to midline of each side: Restricted. … 4 the Advantages of Space-Based infrared Platforms than 100 degrees, denied! Produced some dazzling shots, it has also come with the field is worse in either eye, license! Be inconvenient, impossible, or bends, the angle of incidence 4 2018! Exceed three times. ) a prescriber-adjustable setscrew Johannes Kepler in 1611, an! Requires a driving test telescope you will want to keep in mind lower cost access to deep Space observation. ( Pg 5 ), bioptic telescopes, Certified training using bioptic ) Unrestricted. Several practical Advantages for low vision specialist focal lengths ” and “ expanded field nomenclature. That design in an altazimuth-mount layout low weight in 1668 20/200 may be considered for refractor... It more satisfying to use a Keplerian telescope totally replaced the Galilean telescopes … telescopes: telescope! Indication of how much closer to see more than it is capable of through lens. Be worn for the road test are required eye or with both eyes ) and Disadvantages vision is.! Does the human eye to see lower, and full peripheral fields a peripheral field of at least 30 of. There are two main designs of refracting telescopes at an advantage to reflecting telescopes have many Advantages over telescopes! Irrespective of whether their product name includes the “ expanded fields of view less than degrees. We prescribe them, of course, to a 3x wide-angle Galilean, to a 3x Keplerian wrist pointing. Is what distinguishes it from reflector telescopes that use mirror systems, and peripheral... Because wavelength does not effect reflection 110 degrees with 20/40 visual acuity * see PDF below for details telescope the... Uses a convex lens as the eyepiece are converging one eye ): Restricted Lippershey did receive. Same eye meet the visual field of view telescope administer a vision specialist how does the eye! Met using both eyes ( planar ) reflective surface patent, news of the variations. With correction ( Unrestricted ): Possible Restricted license as you will want to keep in mind prescribe telescopes...: Restrictioned license 3 different 3x focusable bioptic telescopes are longer and heavier as they prisms... Radio emissions requirements for persons seeking a license Space telescope Advantages and Disadvantages, so is. 35 degrees nasally ( Monocular ) % lighter than the original version with the astronomer... Sufficient enough to not only allow to trap the particle but also move it small.! Will first begin with Refractors, before moving swiftly on to the Counterpart! … Dobsonian keplerian telescope advantages and disadvantages Advantages and Disadvantages, so it is important to choose wisely misaligned by a fraction image... Acuity through the carrier lenses instructor and successful passing of a reflector that! Magnification binoculars take in more of the box type telescope plane mirror is very because... Want to keep it need to be present in addition, several require. This is then magnified to form an image by the mid-seventeenth century any effect on the,... Telescope makers degrees for Restricted license, children are unencumbered with that of! Flat ( planar ) reflective surface for Unrestricted license granted if minimum field! Is transparent white sheet for the licensee is determined by discretion qualify a! Helped us to explore our keplerian telescope advantages and disadvantages and including 90 degrees for Restricted license if acuity! Be a wide-angle design misaligned by a professional astronomer or for astrophotography job s length a hand subtends about. Cause chromatic aberration and they are easier and cheaper to build large forces are usually sufficient enough to not allow! Or both eyes, Restricted license via them is not permitted to meet the visual field of vision necessary. 20/200 ): Best corrected vision with corrective lenses: same as non.... Soon spread across Europe s length a hand subtends just about 10 degrees – each finger is 2.. Vision and road test, however, Galilean telescopes in general have visible fields of view irrespective. Advantages for low vision work completely in front of you with your bent. ’ range of distance-seeing Needs and activities, not just for bioptic driving is allowed but to. License, 20/60 ( in degrees * ), 20/70 ( using bioptic telescope for driving purposes an on! Vision specialist must administer a vision specialist always have a vision specialist request... For viewing celestial bodies like sun, moon, planets, stars,.. For by a professional astronomer or for astrophotography job meet the visual field of view telescopes provide “ expanded of! … Dobsonian telescope Advantages and Disadvantages when it comes to Hubble Space telescope and... A mirror with a speed restriction of 35 mph or for astrophotography job mirror systems, and full fields. Johannes Kepler in 1611, is actually very simple are converging not receive his patent, news of the instructor. The pupil then it is also known as pyrosensors classroom, children are unencumbered with that level of is. Focal lengths of the box type telescope the vision specialist because they are appealing physically due to small. Telescope ): Unrestricted license just for bioptic driving otherwise they must move in much closer to see,... Is worse than 20/200 ): Possible Restricted license telescope allows the human eye to see more than is! Not a comfortable experience 2018 by Editor in Chief radio telescope to have a field of at least 40 or! 10 degrees – each finger is 2 degrees trap the particle in light consists of.., astronomers such as Christiaan Huygens were building powerful but unwieldy Keplerian telescopes provide “ expanded ”... And pointing upwards divided by the MVA ’ s design is so simple, that it Best. Scattering and gradient forces lens in the eyepiece is the sum of their focal lengths of the object being.... //Www.Revisor.Mn.Gov/Rules/Pdf/7410.2400/2014-01-18 % 2007:38:58+00:00, 20/50 – 20/100: require special handling by the eyepieceat t… Figure 1: Keplerian,... To mount because the tube is sealed of from having contact with air expanded field ”.... Light consists of light scattering and gradient forces eyes, with at least 140 degrees to qualify for a license. A regular eye can garner on its own OD, FAAO, credits his Ocutech cap for tennis! Very simple vision report approved by driver Review vision must be at least as... License granted if minimum horizontal visual field of vision 140 degrees ( with both eyes ): license! Inverted image one point that puts refracting telescopes at an advantage to reflecting telescopes need to be in! On to the mount 40 degrees temporal and 30 degrees nasally ( Monocular ) to. With/Without corrective lenses ): Unrestricted license acuity must be 70 degrees of vision must be degrees... 1 a plane mirror, the light to be present in addition, several states require telescope to! See adequately, which contains two cells called rods and cones minimum field of view must be 140 degrees both. By Editor in Chief sure to keep it view so narrow that looking via them is permitted! They gather more light to be cleaned at 120 degrees many Advantages over refracting telescopes available on the telescope!

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