THE GALILEOSCOPE (Click Image for Large Annotated View)
THE GALILEOSCOPE is purportedly a high-quality, low-cost refracting telescope kit developed for the International Year of Astronomy 2009. Many will be given away to children and adults to learn how telescopes work and operate, and to repeat some of the celestial observations that Galileo made 400 years ago. (The IYA2009 marks the 400th anniversary of the first use of an astronomical telescope by Galileo.) Cost As of August 10, 2009, the kit was priced at only U.S. $20 each plus shipping for 1 to 99 units, or U.S. $15 each plus shipping for 100 units or more. Galileo Web Site See the Galileoscope web site for more information. This site contains ordering information and educational materials. Very Poor Assembly Instructions 
This kit allows one to assemble a 50-mm diameter, 25- to 50-power achromatic refractor. However, the instructions included with the kit are very poor and make it very difficult to assemble or assemble correctly. The parts list is not only incomplete but also does not include identifying pictures. In addition, some parts included are never mentioned in the assembly steps. Downloading supplementary instructions from the Galileoscope web site for proper assembly is mandatory. Supplementary Assembly Instructions Two supplementary pdf documents are fortunately available through the Galileoscope web site:
Good Optics The Galileoscope kit contains a 50-mm-diameter glued doublet objective lens of focal length 500 mm (giving it an f/10 focal ratio). Also included are six small lenses to make an eyepiece of focal length 20 mm (magnification 25x) and a 2x Barlow lens (yielding 50x) which can be converted into a negative Galilean eyepiece giving about 18x. This type of telescope is often called an achromatic refractor. Although called a Galileoscope, do not confuse this telescope with true replicas of Galileo's telescopes. (His telescopes had woefully poor optics.) The Galileoscoe has superior optics compared to early refracting telescopes. The glass achromatic objective of the Galieloscope produces very good images, especially with the supplied 20-mm symmetrical type eyepiece that you assemble (yielding 25x and an inverted image). Views of the Moon at 25x are sharp and crisp despite some residual chromatic aberration. The four Galilean satellites of Jupiter look sharp and crisp with the low power eyepiece. Nevetheless, banding on Jupiter really requires 50x and the Galilean satellites beomce even more easily visible. I did not observe Saturn since this planet is now too near the Sun. However, one will probably need 50x or more to see the rings, which still may be difficult since the ring system is now almost edge on to the Earth. The phases of Venus will also be difficult unless Venus is near Earth. Still, the Pleiades Star Cluster is beautiful at 25x since the field of view (1.5 degrees) encompasses the entire cluster. The Orion nebula is easily viewed and the double star Mizar splits. I have continued to use the Galileoscope since my first evaluation of this telescope. I continue to be impressed by this telescope's good optical quality. At 25x I easily split Alberio and the Andromeda Galaxy showed nicely. Using inexpensive but good eyepieces improved image quality even up to 80x. Admittedly I "cheated." I also used a sturdy photo tripod with a slow motion adapter! This made using the telescope much easier and helped reduce some of the mechanical difficulties described below. At 50x, the telescope was much more difficult to use even with the slow motion adapter. For example, focusing the telescope severely shakes the instrument and can move the telescope off the object. Once needs considerable patience and skill to achieve a good focus. Beginners and children need to be told about the potential problems listed below that they may face when trying to use the Galileoscope. Eyepieces Difficult to Assemble Eyepieces and the Barlow lens must be assembled using small lenses. Care and dexterity is required. Use tissue paper, lens tissue or gloves to prevent smudging the lenses. Proper assembly using the included instructions is difficult or impossible. However, tube shake may make using the telescope at 50x (using the 2x Barlow) difficult for children and beginners. Download the supplementary instructions to be sure you correctly assemble the eyepieces and Barlow lens. The Galilean negative eyepiece produces an erect image but this eyepiece is almost impossible to use due to its extremely small field of view (a characteristic of this type of eyepiece). This eyepiece is best use to demonstrate how difficult using the first telescopes must have been, which used negative eyepieces. (Of course, the Galileoscope has much superior optics compared with early lens telescopes.) Note: To convert the 2x Negative Barlow into a negative Galilean eyepiece, remove the Barlow optical barrel from the Barlow holder, and attach the auxiliary eyepiece cap to the front of the Barlow optical barrel. The included instructions do not make this clear. Tripod Not Included In addition, the Galileoscope does not come with a tripod; users must supply their own. Fortunately, one can attach the Galileoscope to most photographic tripods. Unfortunately, many acquiring this instrument will not have either a photo tripod or a sturdy enough tripod and will unlikely to buy a sturdy tripod for a telescope that only costs about $20. Even sturdy photographic tripods may not work well with astronomical telescopes since the Galileoscope has a weak point of attachment (a single 1/4-tripod nut) and a long tube that can shake. Unfortunately, even good many photo tripods usually do not have fine motion adjustments. Thus mechanical and design constraints may severely limit the use of the Galileoscope, especially by children or beginners. (The telescope is impossible to use without a tripod.) See also comments on star diagonal and focuser below. Star Diagonal Not Included or Useable The Galileoscope does not include a star diagonal nor can one use a conventional star diagonal to aid viewing. (The Galileoscope will not focus on distant objects if used with a star diagonal.) This can limit or make impossible viewing objects at high altitudes. It also means images seen through the 20-mm (25x) eyepiece are inverted. This is OK for celestial objects but not for daytime scenes. Focusing with Push-Pull Draw Tube The Galileoscope does not have a precision focuser such as a helical or rack and pinion device. Instead one must focus the telescope by moving a focuser tube in or out. (A slight twisting motion helps.) This works fairly easily but tube shake while focusing, especially at higher powers wobbles the tube making precise focusing difficult. Precise focusing may be difficult for beginners, children or those who have little patience. Also, the telescope may move off the object when trying to focus, a serious problem at 50x since the viewing field is much smaller. Since beginners may also have little idea about what celestial objects look like through a telescope, some may think an out-of-focus image of, say Jupiter, is the proper image of the planet's disk! Many people will find using the telescope at 50x very difficult. No Finder The Galileoscope does not have a finder. Instead, the tube has two sighting marks. These work well for daytime viewing but are nearly impossible to see at night. Locating the Moon in the telescope (at low power) is not difficult but can be challenging on other celestial objects. Beginners should be warned to use low power when trying to locate objects. Conclusions The Galileoscope is probably not a good substitute for a "first telescope." Although it has good optics for a beginner's telescope, its mechanical construction and lack of a steady support can limit its usefulness. However, some people may claim the intention of the Galileoscope is primarily to simulate what Galileo used and observed. Still, the Galileoscope's optics is much better than those of very early telescopes. Yes, one can use the Galileoscope to see many of the same objects that Galileo saw. Nevertheless, the images through the Galileoscope will be much brighter, sharper and with better contrast and with a much wider viewing field (with the 20-mm eyepiece) than any instrument Galileo possessed. Thus, one might question whether the Galileoscope really simulates what Galileo used. The primary use of the Galileoscope is likely to be in a teaching environment led by those who can use the Galileoscope to help others better understand what early telescope observers used and observed. Therefore, the Galileoscope is likely to be an excellent "conversation piece" and a good tool under the guidance of knowledgeable teachers. Hopefully, this will awaken children and others to the joys of astronomy and then prompt them to obtain a good first telescope. (Orion Telescopes, for example, sells good beginner telescopes selling for about $50 to $200.) Also see next section. Alternatives to the Galileoscope Note: You can download a pdf version of the following section,"Alternatives to the Galileoscope," here. Inexpensive beginner telescopes are now coming onto the market as the Orion Funscope and the Celestron FirstScope. Each may be a better choice than the Galileoscope for beginners and children. Both offer larger optics (76 mm diameter objectives), with better mechanical construction and a low price. Historically bargain-priced telescopes have been known as "trash" scopes because of poor optics and poor construction including wobbly mounts. Usually, one needs to spend a few hundred dollars to get a good, working telescope. 
These two telescopes, however, seem to have solid mounts and exciting views of popular celestial objects at very low cost (about $50). Both are Newtonian reflector instruments with 76-mm (3-in.) diameter light collecting mirrors (f/3.9, 300 mm focal length). Recall the Galileoscope has a 50-mm. f/10 objective. So, both reflectors collect 2.25x the light compared to the Galileoscope and have theoretically 1.5x more resolving power. Both the Orion and Celestron reflectors also use a rack-and-pinion focuser, an advantage over the Galileoscope. The focusers also accept standard 1.25 in. oculars like the Galileoscope. Both the Orion and Celestron telescopes use altazimuth, Dobsonian type mounts that appear to have good stability. (I have not tested them.) However, these mounts use a table-top design requiring use of a table or flat surface, a possible disadvantage for some people. Nevertheless, Orion states the FunScope's table-top mount has a quick-release dovetail mechanism, so the telescope can be detached and mounted on a tripod. These mounts offer simple left-right, up-down motions and easy viewing even for objects high above the horizon, an advantage over the Galileoscope. The Orion FunScope includes a red-dot finder at no extra cost, an advantage. The Celestron FirstScope does not have a finder but an accessory finder (5x, 24mm) is available as part of a FunScope accessory kit ($20). The kit also has two extra eyepieces (12.5 mm and 6 mm for 24x 50x respectively), a moon filter, instructional CD and nylon carrying bag. Both reflectors come with 15x (20 mm focal length) low power eyepieces that should make finding objects easy. In addition, both include second eyepieces: 30x (10 mm focal length) for the Orion telescope and 75x (4 mm focal length) for the Celestron FirstScope. The Orion Funscope will still need higher powers to see some celestial features (e.g., banding on Jupiter) requiring the user to buy additional eyepieces. Since these telescopes are Newtonian reflectors, the mirrors can occasionally become misaligned and require collimation. Although not difficult, this is a slight disadvantage over the refractor design of the Galileoscope. The Newtonian design produces inverted images making these telescopes awkward for terrestrial viewing. The Galileoscope has the same problem since a star diagonal cannot be used to produce an erect image. (Recall the Galilean eyepiece, which produces an erect image in the Galileoscope, has too small a viewing field to make it a useful eyepiece.) Both companies, like the Galileoscope, suggest downloading pdf files of their detailed instructions. I have not tested either but the 2009 October issue of Sky & Telescope has a brief review of the Celestron FunScope (pp. 40–41). More Information on the Orion FunScope and Celestron FirstScopeThe Celestron FirstScope and Accessory Kit is also sold through Orion Telescopes (estimated ship date 09/01/09): (Also check amazon.com for availability and prices.) Detailed Review of Galileoscope Read a detailed review by Alachua Astronomy Club member, Howard L. Cohen and Assoc. Professor Emeritus, University of Florida. Although the telescope has good optics for an inexpensive telescope, finding objects with the two sights, tube shake which can contribute to focusing difficulties, and lack of a star diagonal may limit its use by children or beginners. In addition, constructing the telescope may challenge some unless the supplementary detailed instructions are downloaded from the Galileoscope web site. Learn how to use this instrument and learn its limitations, or the Galileoscope can be a frustrating experience.
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Return to AAC Home Page Howard L. Cohen Aug. 17, 2009 (revised 2009 Aug. 18, 24, 27, Sept. 24) |