Category How to Find the Apollo Landing Sites

The Refractors

Ask someone to close their eyes and picture in their mind a telescope. Or better yet, ask a child to take a crayon and draw on a piece of paper a picture of a telescope. More likely than not, the image of a long tube pointed at the skies with an observer peering through the opposite end is the result. The refractor is the intuitive concept of a telescope.

Historically, the refractor is the earliest design for telescopes, with the earliest examples appearing in the Netherlands in 1608. Spectacle makers Hans Lippershey and Zacharias Janssen are two of the early creators of the design. Within a year or two Galileo created his own improved refractor design, pointed his telescope into the night sky, and history was made.

Conceptually, a refractor is a system of lenses with an objective lens system to gather light and an eye lens system to focus the light gathered by the objective lens into an image for the observer. Hence, the intuitive mental picture of a long tube with an objective lens pointed at the sky and an observer viewing through the oppo­site end focusing the eyepiece.

Inch-for-inch, refractors are regarded by the astronomy community as the best performing telescopes. Sharp, pin-point star images, and high contrast planetary images are their hallmark. Four inch or larger diameter refractors are the primary instruments of lunar and planetary observers. Astrophotographers have adopted apochromatic refractors as their go-to telescopes, producing the sharp and contrasty images that rival professional observatories.

In today’s world of refractor telescopes, there are achromats and apochromats, terms created to differentiate the levels of color correction of the respective lens systems. Grade school science demonstrates that sunlight passing through a prism separates sunlight into its constituent colors. In optical systems, such as telescopes, all types of optical glasses exhibit some degree of separation and dispersion of light into primary and secondary colors.

The Refractors

A classic achromatic refractor uses a two lens objective, with one lens made of crown glass, and the other lens made of flint glass. With the lenses ground with proper curves and using glasses with different refractive indices, the result is a telescope that can bring to focus two of the three prime colors of light, typically red and blue wavelengths. So conceptually, the achromat can produce an improved image of a distant object over a single lens objective of the type used by Galileo. In practice, there are some color errors, or chromatic aberrations, that creep into the visual performance of an achromatic refractor, especially at shorter focal lengths. The primary colors do not focus at the same point, resulting in a color fringe around Moon, planets or bright stars. This chromatic aberration also results in diminished sharpness and definition in the telescope image. Many classic early refractors typi­cally have focal ratios of f/11, f/15, or f/20 or greater to minimize chromatic aber­rations and become “color-free”. Even at long focal lengths, achromats can display chromatic aberrations, where the secondary colors of yellow and purple wave­lengths do not come to focus.

This technical discussion gives the impression that achromats are flawed. That couldn’t be farther from the truth. Today’s achromatic designs use different types and combinations of Extra-low Dispersion, or ED, glass to lower the chromatic aberrations to a minimum. Modern designs of achromats have minimized the false color to a high degree. One current builder of high quality refractors has taken advantage of new glass technology and our light polluted skies. With a combination of ED glasses, altered lens curves, and adjusting the air spacing between the two lenses of the doublet, the color error in the violet wavelengths match the not-quite – black-really-deep-purple light polluted background sky, resulting in an excellent performing telescope that produces sharp and crisp images with the color error conveniently and cleverly hidden in the background. There are specialized long focus 102 mm achromatic refractors on the market with f/11 focal ratios or greater specifically designed for viewing the Moon and the planets. These modern “planet killers” take advantage of low dispersion glasses and long focal length to provide images that rival apochromatic refractors at one third the cost.

The Refractors

Sometime in the 1980s, the apochromatic refractor became commercially available to the amateur astronomy market. Sophisticated designs appeared using combinations of two, three, or four lenses of exotic glasses. Advanced telescope owners found themselves developing and reveling in a new vocabulary that included terms such as fluoro-crown, lanthanum, fluorite, FPL-51 or -53, APO – triplet, and Petzval. These apochromats offered improved sharpness, contrast, and color correction over the classic achromat refractors, while at the same time creat­ing a more portable telescope with f-ratios of f/8 or less. But this optical perfor­mance improvement is costly. Apochromats are typically 2-10 times more expensive that an equivalent aperture achromatic refractor. Apochromats get expen­sive very quickly as the size increases. A typical 80 mm apochromat retails in the $700 range. A 102 mm triplet can easily cost over $2,500. 130 mm apochromats range fall into the $4,000-$5,000 realm, and you can buy a car with the money needed for larger apochromats.

The old telescope salesman explanation of an achromat refractor is a “color-free image”, meaning no color fringing in the telescopic image. The telescope salesman pitch for an apochromat is “this time, I’m serious! It’s color-free!”. Depending on the sensitivity and sensibility of the observer, the image improvement of an apo – chromat over an achromat can be either a slight or a day-night difference. A lot depends on the sensitivity and sensibility of the refractor owner. From a technical viewpoint, there is no question that the apochromatic refractor offers the best tele­scopic images over an achromatic refractor. In fact, as discussed later in this chap­ter, an argument can be made that an apochromat is inch-for-inch better than every other telescope design, whether refracting, reflecting, or catadioptric.

The Refractors

Countless astronomy books and websites over the years have presented valid arguments that the Newtonian reflector represents the most “bang for the buck” in telescopes. Originally designed by Sir Isaac Newton in 1668, this telescope represents a simple design using either a spherical or parabolic main mirror to collect light and a flat diagonal mirror to reflect the collected light to the eyepiece and the observer. By limiting the number of optical surfaces that need to be accu­rately figured and polished to two, the cost for a Newtonian telescope can be minimized. In contrast, a doublet refractor needs four optical surfaces, and a triplet apochromat needs six optical surfaces to be accurately ground, figured, and polished. The Newtonian design, being reflective in nature, has no chromatic aberrations and can be constructed from less expensive materials. During the explosive growth of Newtonian telescopes in the 1980s, with John Dobson’s unique implementation of the design, Newtonians could be made from Pyrex glass, cardboard tubes, and plywood.

Sounds like the perfect telescope. An 8 in. Newtonian reflector on a Dobsonian mount can be easily acquired for the price of a 3-in. achromat refractor. That is a lot of performance for the money.

But there is a catch. Ask any telescope dealer, any telescope salesman, or any member of your local astronomy club, “What is the most common telescope problem?” Nine times out of ten, owners of Newtonian telescopes are unable to align the optics of their telescopes. The main mirror is tilted, the diagonal is not centered, the tilt of the diagonal needs adjustment, or a combination of all three leads to frustration for the telescope owner, resulting in a telescope that ends up in the closet. Whereas refractors and some catadioptric designs do not need col – limation alignment under normal use, Newtonian telescopes require frequent maintenance. This alignment skill is easily acquired by some, while others find the alignment task difficult. Some telescope owners take collimation in stride, while others find it a nuisance.

The Refractors

The Refractors

Fig. 2.6 The Maksutov-Cassegrain Telescope. Courtesy of Adam Chen

Catadioptric telescopes are a category of telescopes that combine lens and mir­ror technology to produce compact and transportable instruments. With a clever combination of a lens and mirrors, the incoming light path is folded upon itself, and any optical aberrations of the reflecting surfaces can be corrected by the refracting lens.

Catadioptrics are available in two popular forms: Schmidt-Cassegrain tele­scopes, or SCT and the Maksutov-Cassegrain telescope. Maksutov-Cassegrains appeared on the commercial market in the mid-1950s, and SCT’s burst into popu­larity in the 1970s. As a family, catadioptrics offer a high degree of optical perfor­mance and low maintenance in a small compact package.

Although SCTs are available in sizes from 5-in. to massive 14 and 16 in. aper­tures, the most popular and best-selling telescope since the 1970s has been the 8-in. SCT. The 8-in. SCT is the basic core product for not one, but two major telescope companies. The reason for this popularity stems from the all-around versatility that the design provides. As an analogy, the 8-in. SCT is the Olympic Decathlon Champion of telescopes. The Olympic Decathlon gold medalist doesn’t excel in any singular competition, such as the 100 m dash or the high jump, but is able to per­form 10 different events better than anyone else can perform those same events. Versatility and a high level of performance are outstanding attributes of an 8-in. SCT. The 8-in. aperture allows for light gathering for deep sky objects, the typical f/10 focal length enables high magnification for lunar and planetary observations, numerous attachments are available for photographic use, and the compact size ensures frequent usage. But it’s not perfect for any singular use. Newtonian tele­scopes are available at a cheaper price in larger sizes for deep sky light gathering. Refractors produce images that are of better quality in contrast and sharpness. Many amateur astronomers tend to own two, three, or more telescopes in order to optimize their viewing. But if a person is only going to own one single telescope that is capable of handling multiple astronomy tasks, the 8-in. SCT is the likely choice.

Maksutov-Cassegrain, or Maks for short, are highly popular smaller telescopes in the 3.5-6 in. diameter range. Costing from $400 to an astronomical (pardon the pun!) $4,000, these little gems of the telescope world are available in every configu­ration conceivable. Maks tend to have long focal lengths in the f/12 to f/15 range, which helps to improve contrast but limits the field of view. Available on simple manual mounts, to equatorial mountings, to high tech computerized go-to systems, Maks are as versatile as their SCT counterparts. Due to the compact size, Maks make excellent travel scopes.

The natural question that arises from all these discussions of telescope design is: What telescope is ideal? Recalling the car analogy, it depends on the type of observing.

For observing the Moon and planets, the answer is clear. Refractors offer the sharpest, clearest, and most contrasty images. But why? A discussion is needed on the difference between unobstructed and obstructed optics. As seen in Figs. 2.4, 2.5, and 2.6, the Newtonian and the catadioptric designs share a common attribute of a secondary mirror that is centrally located along the light path. These secondary mir­rors allow for the folding of the light path to direct the incoming light to the eyepiece. In the case of the Newtonian, the secondary diagonal serves to guide the light to the side of the telescope to the focuser. In both catadioptric designs, the secondary mirror fold the light path creating a very compact telescope that enables portability. The commercially available Newtonians have secondary mirrors that measure approxi­mately 30-35 % the diameter of the primary mirror. Most SCTs and Maks the central obstruction of the secondary mirror constitutes 40 % the diameter of the primary mirror. The main impact of the central obstruction is a decrease in sharpness and contrast in the telescope image. What is the difference in performance between the unobstructed refractor and an obstructed design? The best analogy is to compare the familiar standard definition TV versus HDTV. A good SCT or short-focus Newtonian will offer a good lunar image like that of a standard 480i digital TV image, but a good ED achromat or apochromatic refractor is like watching a 1080p high-definition TV.

Any of these telescope designs can be used to view the Moon. If the reader of this book currently owns a telescope, proceed to the following chapters and find the Apollo landing sites and enjoy. To those looking to purchase a telescope, the fol­lowing recommendations are offered based on telescope technology, decades of amateur astronomy field experiences, and telescope retail experience:

• For lunar and planetary observing, an 80 mm-to-102 mm refractor is the top choice. These refractors are light, portable, and low maintenance telescopes that offer sharp contrasty images of the Moon and planets. Remember, the reason that large telescopes exist is to act as light buckets and gather the faint distant light of stars, galaxies, and nebulas. The Moon is bright. Really bright. Light gathering is the least of your problems in lunar observing. And when aperture fever occurs, and a larger bulkier telescope is acquired, the refractor takes the role of the easy-to-use, grab-and-go scope. No wasted money here.

• As discussed earlier, it’s hard to argue against an 8-in. SCT. Yes, the lunar images are a little soft compared to a 102 mm apo refractor, but the overall versatility cannot be denied.

• A long focus f/10 or greater Newtonian has a central obstruction approximately 25 % of the primary diameter, and comes very close to refractor image quality. These telescopes are difficult to find in the commercial market, but there are some of these gems on the used market.

• 90-125 mm Maksutov-Cassegrains should also be considered, especially when small size is a requirement.

The Eyepieces

The Refractors

Fig. 2.7 The Author’s Collection of Telescope Eyepieces. Courtesy of the author

Telescope design is only half of the optical story. The rest of the story are the eye­pieces at the focus end of the telescope. And here again, there’s another zoo filled with strange and wonderful denizens that are vying to complete the optical train. Kellner, Abbe, Konig, Brandon, and Nagler are all names of optical designers who have lent their names to their eyepiece designs, and are now an accepted part of the astronomy vocabulary. There are 0.965, 1.25, and 2 in. eyepieces. Some designs have been around for over a century, and some designs are less than a decade old. And most have valid use in astronomy.

The Refractors

Fig. 2.8 (a) Huygens. Courtesy of the author. (b) Ramsden. Courtesy of Adam Chen

Two of the oldest and simplest of the compound eyepiece designs are the Ramsden and Huygens. Originating from the 1700s, these eyepieces serve as historic curiosities. Occasionally, an antique Ramsden will show up at swap meets, eBay, or even antique stores. The Huygens eyepieces are still supplied in 0.965 in. size on cheap beginner telescopes sold at department stores and big-box stores. Both designs are flawed, with narrow apparent fields, chromatic aberration, and short eye relief.

The Refractors

Fig. 2.9 Kellner design. Courtesy of Adam Chen

In the mid-1800s, the Kellner eyepiece was developed by replacing the singlet eye lens element of a Ramsden with a achromat doublet. This resulted in a better performing design with a wider field, better color correction, and less spherical aberrations. When used on long focus telescopes, Kellners still produce a reason­ably good image. The main shortcoming of the Kellner is ghosting when looking at bright objects. So Moon watchers beware! The design exists today under various names, including Modified Achromat, RKE, and modified Kellner. These eyepieces are a good economical alternative for those on a budget.

The Refractors

Fig. 2.10 orthoscopic. Courtesy of Adam Chen

The Refractors

Fig. 2.11 The Plossl orthoscopic. Courtesy of Adam Chen

The Refractors

Fig. 2.12 The Konig orthoscopic. Courtesy of Adam Chen

An examination of the patents for the Abbe, Plossl, and Konig eyepiece designs describes all three as orthoscopic designs. The term “orthoscopic” means free from distortion. In common astronomy vernacular, the term orthoscopic has evolved to become synonymous in name with the Abbe design.

The Abbe has stood the test of time. Since the 1950s, through the growth of amateur astronomy in the 1960s and 1970s, the Abbe design has been highly regarded for sharp and high contrast images. The classic “volcano top” Abbe ortho – scopic, so named for its distinctive beveled shape, are well-known and are highly desired. These Abbe eyepieces have been made by an optician from Japan named Tani-san, whose retirement in 2013 brought an end to decades of Circle T volcano top eyepieces. But don’t fret, Abbe orthoscopic eyepieces are available through other sources. The Abbe orthoscopic eyepiece was held up as the pinnacle of eye­pieces until the advent of new revolutionary wide-angle and high eye relief eye­pieces in the 1980s. Today, dedicated lunar and planetary observers still insist on Abbe eyepieces today.

The Plossl eyepiece has a interesting reputation in the amateur astronomy world. In the 1960s, the Plossl only existed as a rare and mysterious eyepiece, commer­cially available from a small vendor in Europe. Then in the 1980s, Plossls suddenly became widely available, to the point now where it is so commonplace that the eyepiece is considered mediocre by average backyard astronomer. Nothing could be further from the truth. Although poorly manufactured examples exist, a premium Plossl is an extraordinary eyepiece, versatile in lunar, planetary, and deep sky use. There exists a number of variants of the design in which an extra lens or two to the system, somewhat blurring the definition of a Plossl, but these variants tend to be of high quality and offer high performance.

Not as widely available as the other orthoscopics, the Konig design has its fans. Depending on the implementation, the Konig potentially offers a wider field-of – view than the Abbe or Plossl. In practice, the Konig achieves a wider field, but with a slight sacrifice of edge of field sharpness, and slightly shorter eye relief.

A variant of the Konig design is the Brandon eyepiece. Chester Brandon devel­oped his eyepiece design during his time at the Frankford Arsenal in Philadelphia. The eyepiece design was widely used during World War II in U. S. Army optics. The Brandon design differs from the Konig by using three high index glass types and four different lens radii. When marketed in the 1950s as a high priced premium eyepiece, the Brandons were priced at $15.95. My how times have changed, with the price of Brandons and many premium eyepieces in the three-digit range. With sharp crisp contrasty images, the Brandon reputation exceeded that of any other 1950s eyepiece, and is still the go-to eyepiece for many lunar and planetary observers today.

The Refractors

Fig. 2.13 (a) The Erfle. Courtesy of the author. (b) Modern Wide-Angle. Courtesy of Adam Chen

During World War II, a number of scopes used for spotting or for aiming weap­onry by the American armed forces were equipped with Erfle eyepieces. In the 1950s and 1960s, war surplus Erfle eyepieces became available for amateur astron­omers seeking wide-angle views through their telescopes. With an apparent field of view of approximately 60°, these large eyepieces created a demand for wide field eyepieces. That wide-angle demand has grown over the years, to the point now where the consumer demand for ever wider fields of view drives the eyepiece industry. The Erfle does not display as sharp an image in the center of the field as the orthoscopic eyepiece, and a degradation of the image occurs in the outer third of field. Newer modern wide-field designs use exotic glass types and different lens configuration and curves to correct the edge degradation, while at the same time providing a wider field of view.

The Refractors

Fig. 2.14 The Nagler and related ultra wide angle eyepieces. Courtesy of Adam Chen

The quest for an ever wider field-of-view exploded with the introduction of the Nagler eyepiece. Competitors quickly followed, with virtually every telescope company offering their version of an over 80° field-of-view eyepiece. The ante was raised again with the introduction 100° and even wider field-of-view eyepieces in recent years. These eyepieces contain seven or more lenses in their complex designs in an effort to provide wide fields without sacrificing sharpness at the edge of the field. These eyepieces are not cheap, with many exceeding the cost of many telescopes! These eyepieces are outstanding for deep sky and wide field applica­tions. However the complex design, high number of optical surfaces, plus the inevi­table, although slight, light absorption caused by the amount of glass in the light path, these ultra wide angle eyepieces do not offer the same level of sharpness and contrast as the simpler orthoscopic designs.

The Refractors

Fig. 2.15 The Barlow lens. Courtesy of Adam Chen

While not an eyepiece, a Barlow lens is a useful addition to every eyepiece case. A Barlow lens is a negative lens system placed along the light path between the objective and the eyepiece that increases the effective focal length of the telescope, therefore increasing the magnification. Typically, Barlows double (2x) or triple (3x) the magnification. Newer focal extenders using three or four lens elements are available to quadruple (4x) or quintuple (5x) the focal length. These accessories are useful in three ways. A single Barlow lens effectively doubles the number of mag­nifications available in an eyepiece collection. The use of a focal extender also allows longer focal length eyepieces with their higher eye relief to be used at higher magnifications for eyeglass wearers. The use of a Barlow lens can improve the off – axis edge sharpness of some eyepiece designs. The Barlow lens and related focal extenders are also useful for astrophotography.

Some discussion is needed on the subject of zoom eyepieces. In the 1960s, the zoom eyepiece earned a reputation for mediocre optics and was not worth the money. Today’s zoom eyepieces deserve some attention. Improvements in lens coat­ings, the introduction of high index glass, and improved manufacturing has yielded a modern zoom that is worthy of a spot in an observer’s eyepiece case. Although still narrower in field-of-view at longer focal lengths, and wider at shorter focal lengths, the performance has been greatly improved. A zoom eyepiece will not take the place of an eyepiece collection for critical observing, but serves the role for quick look situations, or when showing the night sky to children whose short attention spans don’t allow for the changing and refocusing of conventional eyepieces to change magnification. Viewing the Moon through a 102 ED refractor with an 8-24 mm zoom eyepiece served as an inspiration for the title and subject of this book.

The driving criteria for eyepiece selection for lunar and planetary observing is sharpness and contrast. The rule of thumb for selecting the right eyepieces for view­ing the Moon is “the simpler the better”. The classic Abbe, Plossl and Brandon designs are the preferred choices. There are more esoteric lunar and planetary eyepiece designs based on the monocentric design, or on proprietary designs. These are not discussed here due to their low availability.

There is an Achilles heel to the three classic orthoscopic designs. The older eyepiece designs perform best in longer focal length telescopes. In the era in which these designs originated, telescopes had long focal lengths, typically f/10 or greater. At f/20, even the lowly Ramsden design performs well. But many of today’s tele­scopes have much shorter focal lengths, often f/6 or shorter. The classic designs suffer from loss of edge sharpness because of the steeper angle of the light cone from the objective as it enters the eyepiece. Modern designs take into account the shorter focal length telescopes of today. The design rationale for many of the updated configurations of the Plossl design has been to widen the field-of-view and improve performance with short focal length telescopes.

The recommendation for the ideal eyepiece for lunar observing is as follows:

• For telescopes with a focal length of f/7 or greater, the Abbe or Plossl designs will perform at the highest level.

• For telescopes with focal lengths of less than f/6, the modern variants of the Plossl are suggested.

• For observers who must wear glasses while viewing, there are some proprietary eyepiece designs that provide 20 mm of eye relief. These tend to be premium eyepieces that use exotic lens configurations and glasses, and therefore are not cheap. But they are recommended for eyeglass wearers.

• Consider using a Barlow in combination with a low – or medium-power eyepiece in order to obtain higher magnifications. The comfortable eye relief from this combination is often preferred by both eyeglass wearers and non-eyeglass wear­ers. The classic orthoscopic high power (4 mm and 6 mm) eyepieces are notori­ous for their near-pinhole sized eye lens.

Television Observations

Each Surveyor spacecraft carried a television camera, and more than 86,000 70-mm pictures were obtained at very high resolution (to 1 mm). This photography pro­vided information on the nature of the surface terrain in the immediate vicinity of the spacecraft as well as the number, distribution, and sizes of the craters and boul­ders in the area. In addition to lunar terrain studies, the photography supported investigations of soil mechanics, magnetic properties, and composition of the sur­face material.

Lunar Surface Mechanical Properties

Mechanical property estimates are the result of interpretations of landing telemetry data and television pictures as noted above. Measurements from strain gauges mounted on the spacecraft landing gear were analyzed. The surface sampler, flown on Surveyor 3 and Surveyor 7, also obtained data on mechanical properties. To study soil erosion effects and to determine soil properties, the vernier engines and attitude jets were operated after the landings and the results observed with the television camera. This type of scientific investigation continued during the Apollo missions, with Apollo crews radioing observational information during landing, the impact of rocket exhaust with the surface produced dust clouds, trench digging, and providing core samples for study back on Earth.

Binoculars and Telescopes

Dickinson, Terence and Alan Dyer, The Backyard Astronomer’s Guide, 3rd Ed., Firefly Books LTD., 2008.

This is a comprehensive book that is a must have for any amateur astronomer, beginner or advanced. It provides coverage of telescope and binoculars, astronomical viewing, and astro-photography.

Dickinson, Terence, Nightwatch, 4th ed., Firefly Books, 2006.

One of the most recommended beginner’s guides to the hobby of astronomy. If one has never owned a telescope before, this is an excellent place to start.

Harrington, Philip S., Star Ware – The Amateur Astronomer’s Guide to Choosing, Buying, and Using Telescopes and Accessories, 4th ed., John Wiley and Son, Inc., 2007.

As the subtitle states, this book is highly recommended to help the sort through the maze of equipment available for anyone in the market for astronomy equip­ment. This book provides a consumer’s guide of most of the brand name astronomy equipment available in the marketplace.

Consolmagno, Guy and Dan M Davis, Turn Left at Orion, Cambridge University Press, 1989.

An excellent observer’s book highlighting a hundred night sky objects that can be seen through modest sized telescopes. A section of the book is devoted to the Moon, with galaxies, nebulae, and star clusters comprising the rest of the book. The beauty of this book is its presentation of each objects view as seen naked eye, though a finder scope, and then through the eyepiece of a telescope. Highly recommended.

The Filters

As the Moon waxes towards its full phase, the image through a telescope becomes uncomfortably bright. Not dangerously bright as with the Sun. Just so bright that the viewing can become difficult to identify areas on the Moon without squinting.

There are a number of filters available to telescope owners, such as nebula fil­ters, light pollution filters, and color filters. These filters are very useful in many applications where the goal is to reveal very dim low contrast objects and features. But viewing the very bright Moon does not require these sophisticated accessories. The goal of using neutral density filters is to dim the light entering the eyepiece without any major degradation of image quality. With two polarizing filters, the same can be accomplished. By turning the filters in respect to each other, the amount of filtering can be adjusted.

It is recommended that one or two neutral density filters or polarizing filters be available to cut down the intensity of the incoming moonlight. These filters conve­niently screw onto the bottom of the eyepiece. They cost less than $20, and are well worth the investment.

The Mounts

The Filters

Fig. 2.16 The Author’s telescopes featuring an Alt-Az with Slow Motion Controls, two German Equatorials, and Computerized GOTO Mount. Courtesy of the author

A solid telescope mount completes the total system needed for viewing the Moon, and beyond. There are two basic flavors of mounts: the altitude-azimuth mount, mostly referred to as the Alt-Azimuth or AltAz mount; and the equatorial mount. Each type can come either as manual, driven by hand controls or motors, and computer-driven GoTo models. Equatorial mounts and some computer-driven mounts compensate for the Earth’s rotation and will track the Moon, planet, or other celestial object, thereby keeping the object in the field of view of the telescope.

The Filters

Fig. 2.17 AltAzimuth mount with slow motion controls. Courtesy of the author

The most intuitive and easiest telescope mount is the altazimuth mount. Right – left and up and down. Simple in operation. In fact, it’s the perfect mount for young people to use. Four year old kids have been seen at star parties using a refractor on an alt-az mount viewing the Moon with little supervision. Altazimuth mounts are considerably lighter than equatorial mounts, and are therefore well suited for grab – and-go scopes or for traveling. No set up is needed. The main drawback is the lack of tracking. The observer manually adjusts the positioning of the telescope, becom­ing the human tracking motors!

The Filters

Fig. 2.18 The Dobsonian Mount. Courtesy of Gary Hand

A notable example of an alt-azimuth mount is the implementation made famous by John Dobson in the early 1980s. Known as the Dobsonian mount (with the entire assembly including the Newtonian telescope being referred to as the Dobsonian telescope), is a simple, low center of gravity alt-azimuth mount made of wood and Teflon bearings. The Dobsonian caused a resurgence in homemade telescopes in the 1980s and 1990s. In today’s market, telescope manufacturers dominate the 12-in. Dobsonian and smaller sizes because of the economies of scale. Larger sizes are economically attractive for homebuilt projects, and for those with the funds, can be obtained as commercially produced telescopes. The Newtonian telescope on a Dobsonian mount offers by far the biggest “bang-for-the-buck”. But they are big, bulky, and the Newtonian optics still requires frequent alignment. For Moon and planetary use, Dobsonians are not recommended for the mechanically challenged.

The Filters

Fig. 2.19 German Equatorial Mount. Courtesy of the author

With the exception of fork mounted Schmidt – and Maksutov-Cassegrains, the most popular form of equatorial mount in the amateur world is the German equato­rial. The German mount is a tilted axis contraption with the right ascension axis pointed and aligned in the direction of the North Pole (for those down-under, the South Pole). A tracking motor applied to the right ascension axis drives the mount to keep the observed object in the eyepiece. German equatorial mounts are awk­ward and heavy. Care must be taken to balance the telescope on the mount, which explains the presence of the large counterweight that is a characteristic of the design. And polar aligning of this mount can be a chore. But if astrophotography is a goal, the German mount is a necessity.

The Filters

Fig. 2.20 Computer GoTo Mounted Schmidt-Cassegrain. Courtesy of the author

A GoTo telescope mount is quite simply a telescope system that is able to find celestial objects in the night sky, and then track them. The GoTo mount can be set up in an alt-azimuth or equatorial fashion, and after the proper alignment proce­dure, the finderscope is not needed for the rest of the evening. Some of the newer GoTo telescopes have electronics that will perform the alignment procedure automatically.

These telescope mounts are wonderful pieces of technology. The GoTo technol­ogy allows for more efficient use of observing time by quickly finding objects in the night sky. Built into the hand controller is a microprocessor, firmware, and built-in memory catalog of the positions of thousands of stars, galaxies, nebulae, open star clusters, globular clusters, planetary nebulae, our solar system planets, and of course the Moon. And the Moon is the one object that does not need a com­puter assist to find.

There is a tradeoff when buying a GoTo mount. These mounts are not cheap. Often consumers are faced with the dilemma of either a smaller telescope with a GoTo mount, or a larger aperture telescope on a non-computerized mount. In the case of viewing the Moon, a GoTo mount is not needed. If you can’t find the Moon, it’s either during the new moon phase, or you’ve got other problems! The Moon is an easy target.

A tip to GoTo owners: When using a telescope on an alt-azimuth GoTo mount, always use Polaris as one of your alignment stars. The computer algorithm used in programming the mount goes through less mathematical gymnastics when aligning with declination 0°, right ascension 0°. The GoTo accuracy is improved tenfold.

Lunar Surface Soil Mechanics

The soil mechanics investigation was performed by the surface sampler carried on Surveyor 3 and 7. The sampler proved to be an extremely versatile and useful piece of equipment. Using this device, operators performed a number of bearing and impact tests and trenching operations. All these operations were monitored using the television camera, and photography of the results provided information for this investigation. This type of scientific investigation also continued during the Apollo missions, as Apollo crews performed many observational and sampling tasks related to soil mechanics.

Lunar Surface Electromagnetic Properties

Surveyor 5, 6, and 7 had a magnet attached to one of the spacecraft footpads to determine magnetic properties and composition of the soil. Surveyor 7 had addi­tional magnets on a second footpad and the surface sampler. Photographs showing the amount of dust adhering to magnets indicated the amount of magnetic particles in the soil and allowed estimates of the lunar soil compositions when compared with pre-mission experiment photographs of magnets in terrestrial soils of various compositions. On a larger scale, the ALSEP suite of the Apollo missions carried a lunar surface magnetometer to measure the strength of the Moon’s magnetic field.

Author’s Telescope. Equipment. Used for This Book

The initial thought in the creation of this book was to use 100 % NASA produced photographs from full moon, to the zoom-in shots, to LRO photos, and to Apollo astronaut shots.

But as the book evolved, to produce the view that a backyard observer would see, it became a necessity and challenge to produce lunar photographs of the full moon and the telescopic views myself.

I own several telescopes that are capable of producing outstanding lunar images, and I initially used three refractors of mine: a 94 mm and a 130 mm Brandon apo – chromatic refractors, and a 102 mm Stellarvue 102ED refractor. Since refractors produce the sharpest and most contrast images, I felt the aperture ranges were representative of telescopes commonly owned by potential readers of this book.

The two Brandon refractors are legendary late-1980s telescopes and highly sought after, since at their heart are Astro-Physics triplet apochromatic objectives. Both Brandon refractors are mounted on Vixen German equatorial mounts, with the 94 mm on a 1980s vintage Super Polaris mount with right-ascension drive and manual declination drive, and the 130 mm on a Vixen Sphinx SXW dual-axis drives and computerized STAR Book control. The challenging aspect of using these tele­scopes are their somewhat archaic Unitron rack-and-pinion focusers, which for visual use are perfectly adequate, but for photographic use lacks finesse and made high magnification fine focusing challenging. Prime focus projection was used for full Moon photos using these telescopes.

The Stellarvue 102ED is a more recent late-2000s vintage, using modern low – dispersion ED glass and a two-speed Crayford focuser. The two-speed Crayford focuser facilitated fine focusing for the higher magnification photographs. Higher magnifications were achieved using Barlow lens projection in combination with extension tubes. The Stellarvue 102ED is mounted on a common mid-priced CG-4

German equatorial mount with dual-axis drives. Although the CG-4 lacked the sophistication of the Vixen mounts, the short exposures used in producing lunar photos did not require high precision or any fine adjusting guidance from the mount.

An affordable digital single lens reflex, or DSLR, camera was used. A Canon XTi DSLR equipped with the appropriate T-mount and T-adapter was used. Exposures ranged from as short as 1/800 second for full Moon shots to 1/60 second for the gibbous Moon. Initially, the photos were jpg-compressed, but as experience with the camera-telescope combination was gained, the RAW format was used to facilitate post-processing of the photos using RegiStax and Photoshop software.

In the end, I found the Stellarvue produced the best photographs, mostly the result of the combination of high quality optics with a excellent dual speed Crayford focuser. All of the author’ produced photos in this book are the result of several clear evenings during February and March, 2012 using the Stellarvue 102ED and the Canon XTi DSLR. Post-processing of the digital images were per­formed on an Apple iMac using Adobe Photoshop.

The Binoviewer Option

The Binoviewer Option

Fig. 2.21 The binoviewer. Courtesy of the author

The majority of telescope owners make their observations through an eyepiece using one eye. The human brain is designed to process visual images through two eyes. There are two options for viewing the Moon, the planets and stars with two eyes. One is REALLY expensive – binocular telescopes. The other option is rela­tively affordable – the binoviewer. The binoviewer uses a system of prisms to split the single light path of a telescope into two separate light paths to two eyepieces. This beam-splitting fools the eyes and the brain into thinking it is seeing an object in stereo. The results are spectacular when viewing the Moon. At certain high mag­nifications, and by allowing the Moon to drift through the field-of-view, the observer gets the sensation of orbiting the Moon and seeing the view that the Apollo command module pilot would see in orbit. With both eyes open, the lunar landscape seems to glide smoothly past. Even when tracking, the lunar landscape seems to take on three dimensions. The downside to owning a binoviewer is threefold:

• There is a slight light loss using a binoviewer because of the additional light splitting optics. But for a bright object like the Moon, this is not a problem. For planetary views, the light loss is not of great impact. Deep sky observing can be problematic, especially with dim objects.

• There is the additional expense of the binoviewer and buying two of every eye­piece. And you are limited to 1.25 in. sized eyepieces.

• Many telescopes do not have enough in-focus to accommodate a binoviewer. SCTs and Maks focus by moving the primary mirror and binoviewers work well with these types. Some refractors are manufactured with shorter tubes to accom­modate the binoviewer, and provide extension tubes to use for mono viewing. Many binoviewers have an optional Barlow-like attachment to allow focusing with other types of telescopes, which limits the low power magnification range.

Alpha-Scattering Chemical Analysis

Composition of surface materials was also determined from data obtained by the alpha-scattering instrument. The alpha-scattering surface analyzer was designed to measure directly the abundances of the major elements of the lunar surface.

This instrument was carried by Surveyor 5, 6, and 7 to allow chemical analysis of the lunar surface material. The alpha-scattering surface analyzer performed as designed, and provided excellent data. From the three Surveyor spacecraft that carried the alpha-scattering surface analyzer, six lunar samples were examined. The Surveyor 5, 6, and 7 missions provided the first chemical analysis of lunar surface material.

In summary, five Surveyor spacecraft landed successfully on the lunar surface. Four of these examined widely separated mare sites in the Moon’s equatorial belt. The fifth investigated a region within the southern highlands. Four spacecraft sur­vived the extreme cold of the lunar night and operated for more than one day/night cycle. In total, the five spacecraft operated for a combined elapsed time of about 17 months, transmitted 87,000 pictures, performed 6 separate chemical analyses of surface and near-surface samples, dug into and otherwise manipulated and tested lunar material, measured its mechanical properties, and obtained a wide variety of other data that greatly increased our knowledge of the Moon.

The Recommendation

Many of the readers of this book already own a telescope, on a stable mount, with a case or two of eyepieces and accessories. These readers are suitably equipped to observe the Moon and search for Apollo.

To the readers without a telescope, get one. Astronomy is a wonderful hobby, filled with potential personal discoveries. For the price of a pair of bifocal high index eyeglasses, a nice 80 mm refractor on an alt-azimuth mount with two Plossl eyepieces can be obtained. This setup serves as a great care free introduction to the hobby, and when aperture fever takes hold (it always does) and a larger telescope is procured, the 80 mm refractor still has a role as a grab-and-go scope. The 80 mm refractor’s sharp images are always appreciated.

Crash Sites. of Saturn Third. Stages and LM. Ascent Stages

The ultimate observational challenge (and extra-extra credit!) is sighting and identifying the impact sites of the Saturn IVB third stages and LM ascent modules. Not all impacted on the Moon. As with the Apollo landings sites themselves, the impact craters of the Saturn IVB and LM stages are not large enough to be viewed directly with backyard telescopes. The third stage impact craters are about 100 feet or so in diameter, far too small to be seen with Earthbound telescopes. The S-IVB and LM impact sites tended to be in the same general vicinity as the landings them­selves, as seen in Fig. 12.1. Good luck in identifying these sites!

J. L. Chen, How to Find the Apollo Landing Sites,

The Patrick Moore Practical Astronomy Series, DOI 10.1007/978-3-319-06456-7_12, © Springer International Publishing Switzerland 2014

Apollo 15 KM Impact

Apollo 17 LM Ascent Stage

Apollo 14 LM AscenDStage Apollo 12 Landing Site

Apollo 15 S-IVR Impact & Agollo irS-IVB. .

Apollo 13 S4VB

. Apollo 14 S-1VB – ^ * 2^-

Apollo_16 S-IVB

Fig. 12.1 Locations of Saturn IVB and LM Ascent stage Impacts. Courtesy of the author

Fig. 12.2 LRO view of the Apollo 13 S-IVB Third Stage Impact Site. Photo courtesy ofNASA and Arizona State University

The Apollo 13 third stage Saturn-IVB was the first deliberately sent to impact the Moon. The spent S-IVB third stage separated from the Command/Service Module and later impacted the moon north of Mare Cognitum. From the tracking of the radio signals of the rocket, the impact locations on the moon and the impact times were fairly well known. Figure 12.2 was taken by the LRO in 2009.



At the time of the Apollo 13 mission, only the seismometer at Apollo 12 was available, which had been deployed 5 months earlier. The S-IVB impact occurred on April 14, 1970, at a distance of 135 km from that seismic station at longitude 332.11°, latitude -2.56°, elevation 1,166 m. The later Apollo missions all took advantage of their third stages by impacting them on the Moon. With an expanding network of seismometers with each subsequent mission, impacting the known size and weight of the S-IVB third stage served as a calibration tool for all the ALSEP seismometers. The impacts by the S-IVB stages represented unique calibration signals for the Apollo seismic station network, which operated on the lunar surface from 1969 to 1977. Since the rocket impacts occurred at known times and places, the seismic wave velocities, in particular those within the upper lunar crust could be measured directly.

Fig. 12.4 Apollo 14 S-IVB Impact crater taken by LRO. Photo courtesy of NASA and Arizona State University

Upon the return of the Apollo 14 crew to the CM Kitty Hawk, the ascent stage of Antares was sent to the surface of the Moon to provide seismic data. The ascent stage of Lunar Module Antares impacted the Moon on February 6, 7:45 PM EST, at longitude 3.42° S latitude 19.67° W. Both the Apollo 12 PSE and the newly setup Apollo 14 PSE recorded the Antares’s impact, which occurred between the two seismometers. The resulting impact rang for an hour-and-a-half, with both ASE setups recording the event. Antares’ descent stage and the mission’s other equip­ment remain at Fra Mauro at 3.65° S and 17.47° W.

With the precedent established with the Apollo 13 S-IVB third stage, the Apollo 14 Saturn third stage was intentionally impacted onto the Moon at longitude 8.09° South and latitude 26.02° West. Again, this event provided data to the Apollo 12 PSE using a known size and mass.

The LM Falcon, after returning Apollo 15 astronauts Scott and Irwin to Endeavor, was jettisoned and impacted the Moon on August 3, 1971 at 26.36° N and 0.25° E. The empty discarded LM impacted west of the Apollo 15 ALSEP on the other side of valley, roughly 6 miles away from the Apollo 15 ALSEP deploy­ment. Backyard observers viewing the Apollo 15 landing site need only shift their attention to westward to view the impact area of the Falcon.

The Saturn S-IVB third stage impacted the Moon on an earlier of July 29, 1971 at latitude 1.51° S and longitude 11.81° W. The Apollo 15 Saturn IVB impacted relatively near the Apollo 14 ALSEP. So viewing the Apollo 14 landing site will encompass to the east the impact site of the Apollo 15 third stage.

Both the Falcon and the S-IVB impacts were recorded by the PSE network which now included the PSE at the newly deployed Apollo 15 ALSEP at Hadley Rille and the Apennine Mountains.

Upon the return of the Apollo 16 crew to the CM Casper, the ascent stage of the LM Orion was intended to impact the Moon to provide seismic data. The ascent stage of LM Orion separated 24 April 1972, but a loss of attitude control rendered it out of control. It orbited the Moon for about a year. The Orion impact site on the Moon is unknown.

With the precedent established with the Apollo 13, 14, and 15 S-IVB third stages, the Apollo 16 Saturn third stage was intentionally impacted onto the Moon at longitude 1.3° North and latitude 23.8° West. This event provided data to the PSE network of created by Apollo 12, 14, 15 and 16 using a known size and mass.

Fig. 12.5 Apollo 17 Saturn IVB Third Stage after Jettison. Courtesy of NASA

Apollo 17’s LM Challenger ascent stage was sent crashing into the Moon, with the impact recorded by the ALSEP geophones left behind by Apollo 12, 14, 15, 16, and 17. NASA reported the ascent stage impacted the Moon at coordinates 19.96 N, 30.50E at 1:50 EST on 15 Dec 1972.

The spent Saturn IVB third stage for Apollo 17 impacted the lunar surface at 4.21S latitude, 12.31 W longitude at 3:32:42 pm EST on 10 Dec 1972.

As an additional note, the LM that did not land on the Moon from Apollo 10, called Snoopy, is lost in heliocentric orbit and efforts are underway to re-acquire it. British amateur astronomer Nick Howes embarked on a mission to find Snoopy. He’s looking for Apollo 10’s lunar module Snoopy, which is believed to be in an orbit around the sun, and is the only intact lunar module used operationally from the Apollo program. Howes is using a blink comparator, a machine that allows astronomers to rapidly shift back and forth between two images of the same part of the sky taken days or weeks apart. Movement of Snoopy can be detected by a change in position of an image against the background of stationary stars. Blink comparators used to be a manual devices, alternately shining a light behind two different images; modern astronomers have the luxury of computer software that shifts between images for them. Historically, a blink comparator is how Clyde Tombaugh found Pluto, painstakingly and manually flipping between two images at a time at the Lowell observatory in Flagstaff, Arizona. This technique is also how Mike Brown found the trans-Neptunian object Eris, which ultimately lead to Pluto being demoted from planet to a dwarf planet.

After Apollo 10 completed its successful rendezvous in lunar orbit, Stafford and Cernan transferred from Snoopy back into CM Charlie Brown. With all three men settled in their return spacecraft, they closed the hatch between the LM and CSM and separated, sending the LM Snoopy into deep space. The craft had no purpose beyond the dry run for a landing and like all lunar modules wasn’t equipped to come back to Earth. Mission control fired Snoopy’s ascent engine for 239 seconds to full depletion, using up all of its available fuel. This depletion firing sent the lunar module into an orbit around the Sun. The crew watched Snoopy gain speed as it disappeared into the distance.

With Snoopy’s portion of the mission complete, Stafford, Cernan, and Young went back to tracking landmarks on the moon’s surface. Their survey lasted 31 lunar orbits, after which they fired CSM Charlie Brown main engine for the return to Earth.

Neither the crew nor NASA paid attention to Snoopy’s fate after the jettison. NASA does, however, know where and when the LM separated and how fast the spacecraft was going. With this data, Howes can calculate its rough orbit and effec­tively shrink the area where the hunt for Snoopy will take place. The search for Snoopy will be difficult, but with enough photographic data and an approximate area to search, and a little luck that the lost LM will reflect enough light into the telescopic CCD chips to register, Snoopy may be found.