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📷 | Anyone can easily see the universe!"Vespera", a device that combines an astronomical telescope and a camera


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Anyone can easily see the universe!"Vespera", a device that combines an astronomical telescope and a camera

 
If you write the contents roughly
Since "Vespera" has no eyepiece, you cannot experience the astronomical observation of "looking through an astronomical telescope and seeing the celestial body with the naked eye."
 

Some knowledge and skill were required to perform astronomical observation and astronomical photography.However, the astronomical telescope and the camera are in one ... → Continue reading

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Wikipedia related words

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Astronomical telephoto

Eyepiece

Eyepiece(Boil cancer lens, British: ocular), What istelescope,binoculars,microscopeA lens that is attached to the side of the optical device that comes into contact with the eyes.Objective lensAnd made to focus by the light collected by the primary mirrorReal imageTo expand.Eyepiece(British: eyepiece).

Many optical instruments have a mechanism for adjusting the mounting position of the eyepiece for focusing.

Most telescopes and microscopes can be replaced with eyepieces with different magnifications so that the magnification can be adjusted.

History

Galileo GalileiThe eyepieces used in telescopes of the era are concavelensIt was.An eyepiece with a concave lens has the advantage of producing an upright image, but has a major limitation that the field of view is narrow and the magnification cannot be increased.

Johannes KeplerIs a two-disc convex in 1611lensI devised a telescope with an eyepiece.By doing so, it became possible to freely change the magnitude of the magnification of the image that can be seen by the eye, and since then, it has become common for eyepieces to be convex lenses.

When a convex lens is used, the image becomes an inverted image, but Kepler used two lenses to invert the image twice to make an upright image.Since it is unlikely that an astronomical telescope or microscope will have an upright image, it is now used as an inverted image.In the optical path when an upright image is required, such as binoculars and ground telescopesprismIs added to invert the image again.

Early telescope eyepieces were single-lens, but single-lensaberrationThe optical performance is poor because it cannot be corrected.Therefore, eyepieces have been developed by combining a plurality of lenses to correct various aberrations.Multiple lenses are laminated to make one bonded lens, and these bonded lenses are further combined to form one eyepiece.The combination of these lenses is the type of eyepiece.When the total number of lenses used is m and the number of laminated lenses made by combining them is n, it is called a lens with m elements in n groups.It is usually called as a formula with the name of the creator.

Recently, many eyepieces have been announced with a concept other than reduction of aberrations, such as those that provide a wide field of view and those that can be easily seen even with glasses on.

Types of eyepieces

The explanation here is a concise summary of what is generally described in optical books and telescope manuals, or is an appropriate modification.However, in such literature, many pages are devoted to classic eyepieces, and few of the recent designs are mentioned.Therefore, it should be noted that there are many types of eyepieces on the market that are not listed here.Moreover, the commercially available product is not manufactured according to the design of the inventor introduced here.The abbreviation is a letter engraved with the focal length to indicate the type of eyepiece on the housing of the eyepiece. For example, HM-25mm means Mittensee Heigens with a focal length of 25mm.

Hygens or Huygens (Huygens, Abbreviation H)
An eyepiece with 2 elements in 2 groups made by combining two large and small lenses with one side convex and one side flat. 1703ToChristian HuygensAnnounced format[1]..It is often called Huygens or Heigen in telescopes and Huygens in microscopes. 1865Around Moritz Mittensee changed the lens on the side of the Hygens objective.Meniscus lensAberration is reduced instead of[Annotation 1]Mittensee Haigens or Mittensee Huygens (Huygens-Mittenzway orModified Huygens, AbbreviationHMOrMH).Of the lensadhesive OfHeat-resistantIt was recommended as an eyepiece for observing the sun when it was bad.

Ramsden (Ramsden, Abbreviation R)
An eyepiece with 2 elements in 2 groups made by combining two lenses with the same convex surface on one side and a flat surface on one side so that the convex surfaces face each other. 1783Format announced by Jesse Ramsden in[1]..It is not suitable for telescopes due to its large chromatic aberration.It is an eyepiece with little distortion, and the focal position is on the outside of the two lenses, so crosshairs and scales can be added later.Therefore, for inspectionMagnifying glass,microscopeIt is used for such purposes.It is rarely seen as a stand-alone product.Of the lensadhesive OfHeat-resistantIt was recommended as an eyepiece for observing the sun when it was bad.

Kerner (Waiter, Abbreviation K)
Carl Kellner 18492 groups 3 sheets format announced for microscopes[1]..The Ramsden type lens on the eye side is used as an achromatic lens.Chromatic aberration is relatively small and the field of view is relatively wide.It is used at medium to low magnification regardless of whether it is a telescope, binoculars, or a microscope.In the past, it was distributed in large numbers, but now it is rarely seen.

Orthoscopic (Orthoscopic, Abbreviations Or, OR, O)
Orthoscopic means "a neat statue".Initially, the term was used for Kellner eyepieces, but it was so exaggerated that it did not take hold.[1]..The Abbe type and Presle type, which will be described later, have small distortion and are often sold under this name.[Annotation 2].
Abbe (Abbe, Abbreviation A[Annotation 3])
1880ToErnst AbbeAnnounced for microscopes[1]..Has high optical performance.

Presle (Plössl, Abbreviation PL)
1860To(German version)Announced for a magnifying glass as an improvement of the Kellner style.[1]..High optical performance like the Abbe type[Annotation 4]..This is the most popular type of classic eyepiece today.In Japan, it is misrepresented as Procel or Prozel for some reason.

Elfre (Erfle, Abbreviation E or Er)
1917から 1918OverHeinrich ErfleHas developed several types of eyepieces for military binoculars.Usually, the Elfre type refers to an eyepiece with 3 elements in 5 groups that provides a wide field of view. One group is a single lens and the remaining two groups are two laminated lenses.For low magnification.It's well known, but it's not really made that much.

Konig (King, Abbreviation Kö)
Albert König has developed several types of eyepieces.It should be noted that simply saying the Konig formula does not refer to a specific format.Among them, there are the ones that are mass-produced by improving the Abbe type, the eyepieces with 2 elements in 3 groups with the objective side lens attached as opposed to the Kellner type, and the ones for wide field of view like the Elfre type. is there.

Nagler (Nailer)
Developed by Teleview Al Nagler 1980An eyepiece with a super wide field of view released in Japan.This success triggered the launch of wide-field eyepieces by various companies.There are several variations, and even Type VI is currently on sale.


Telescope eyepiece

The eyepiece of the telescope has an alphabetical abbreviation indicating the type and the focal length in mm.In addition to this, as the spec value of the eyepiece often described in the catalog,Apparent visibilityとEye reliefThere is.

Performance (appearance) differs depending on the type of eyepiece.Each company sells its own wide-field eyepieces.

Of the telescope body and eyepieceFocal lengthBy the combination ofmagnificationChanges.The magnification is the focal length of the objective lens or primary mirror divided by the focal length of the eyepiece.The shorter the focal length of the eyepiece, the higher the magnification.You can increase the magnification as much as you want by using an eyepiece with a short focal length.However, since the amount of light entering the lens barrel has not changed, the image becomes darker as the magnification is increased.Also, since the resolution is determined by the aperture of the telescope, even if the magnification is increased, the details cannot be seen.Therefore, there is no point in increasing the magnification unnecessarily because it only becomes dark and blurry.For telescopes with a small aperture, the limit for practical use is about 15 to 20 times the value expressed in cm.

The majority of eyepieces have a common mounting size for each company.Depending on the diameter of the insertion part24.5mm size(Also called Zeiss size, German size, Japanese size)31.7mm size(American size, 1.25 inch size, also called 1 inch size[Annotation 5]),2 inch sizeThere is a distinction (50.8mm, which is also called American size) (there are other 36.4mm screw type and 50.8mm screw type, and the manufacturer's own size).In the past, 24.5 mm, and now 31.7 mm and 2 inch sizes are the mainstream.

Apparent visibility

Apparent visibilityIs the angle that can be seen when looking through the eyepiece.When the apparent field of view exceeds 65 degrees, it is often called wide field of view, and when it exceeds 75 degrees, it is often called ultra wide field of view.Most of the classic eyepieces have an apparent field of view of around 40 degrees.

The actual visible range of the object isReal field of viewIt is called, and it is roughly the apparent field of view divided by the magnification.For example, if an eyepiece with an apparent field of view of 40 degrees is used at a magnification of 80 times, the actual field of view is about 0.5 degrees, and the full moon can be seen in a range that fits perfectly into the field of view.

Eye relief

Eye relief(British: Eye relief, pupil distance) is the distance from the apex of the lens surface closest to the eye to the exit pupil.[2]..When looking through eyepieces with the same pupil diameter, the longer the eye relief, the farther away you can see the entire field of view.The position of the exit pupil is the eye point (British: Eye point), and the long eye relief is called the high eye point.astigmatismIf there isglassesYou will have to look through the telescope with the eye relief on, but at this time, the outer periphery of the field of view will not be visible unless the eye relief is about 15 mm or more.Basically, the shorter the focal length of the eyepiece, the shorter the eye relief.HoweverBarlow lensBy incorporating the eyepiece into an eyepiece with a long focal length (smile lens), it is possible to design a long eye relief despite the short focal length, and such an eyepiece is also commercially available.

Microscope eyepiece

In a microscope, unlike a telescope, the magnification is changed by exchanging the objective lens, so it is not exchanged very often.

The magnification is written on the eyepiece of the microscope, which is the clear vision distance (about 25 cm or 10 in the shortest distance that an ordinary person can focus on when viewed with the naked eye) divided by the focal length of the eyepiece. It is a thing.

Also instead of apparent visibilityNumber of fields of viewIs used.This indicates how many mm of the range is within the field of view at the position of the clear viewing distance.The actual field of view is the number of fields of view divided by the magnification of the objective lens.

The eyepieces of microscopes are not particularly different from those of telescopes and binoculars.However, since the eyepiece sleeve is φ23.2 mm, the eyepiece of the telescope cannot be used as it is.

footnote

[How to use footnotes]

注 釈

  1. ^ Not usually called Heigens Mittensee.
  2. ^ However, most of the actual products are quite distorted.It is said to be designed to give priority to securing the pupil distance.
  3. ^ Isn't the eyepiece that actually uses this abbreviation the only Zeiss product released in the 1990s?
  4. ^ However, in reality, there are many cheap items, so the name value is not as high as Abbe.
  5. ^ If you convert 1.25 inches to millimeters, isn't it 31.75mm size, or rounded to 31.8mm size?You might think, but it's customary in the telescope industry today to call it the 31.7mm size.

Source

  1. ^ a b c d e f "Telescope Optics and Refraction for Astronomical Amateurs" pp.201-234 "Eyeglasses".
  2. ^ Optical Technology Glossary

References

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