TRG – Telescope Review Guide

Orion’s Skyquest XT4.5 is the smallest in their Dobsonian line of telescopes that includes the XT6 , XT8 , and XT10. Newcomers to the hobby are always surprised at how large amateur telescopes are, but to experienced observers, this XT4.5 is considered a very small scope. Tiny, in fact (It’s so small, astronomers are buying them just because they think they’re so cute). Make no mistake, though–the XT4.5 is a full-fledged telescope, and is a serious observing tool that could last you for years.

Your money buys you a lot in this case. Included are a good-quality 4.5″ f/8 primary mirror, two eyepieces, a finder, and a CD-ROM with a stripped-down version of The Sky, a software guide to the sky. The scope comes in two cartons. One contains the optical tube, and the other is a flat-packed box containing the base, which you assemble yourself. Orion includes all the hardware and tools you need, and the instructions are well written. Allocate about 30 minutes to assemble and align everything.

There are a couple of cost-cutting measures. The primary mirror is spherical, not parabolic (this is not likely to affect the views, however). Also, the focuser is plastic. Plastic focusers are naturally less robust than metal ones. Finally (and this may be the most serious concern of all), the scope is a little short for an adult. The eyepiece is only 3 feet off the ground, which may force you to stoop over (hint: try sitting on a short chair or stool while observing). On the other hand, the height is ideal for a child, making this a great telescope for kids.

Under the stars, the XT4.5 exhibits excellent performance. Once properly collimated (aligned), the optics give clear, sharp, contrasty views.  Jupiter’s cloud band and four moons are no problem to see, nor are Saturn’s rings. The Orion Nebula is a glowing fan of green gas, with a quartet of tiny stars at its core. Under dark skies (and with some diligence) the XT4.5 can even pull in some of the fainter deep sky objects, like the brighter galaxies in the Virgo Cluster.

As recently as a few years ago, the old adage regarding telescopes was that you must spend at least $300 to avoid buying junk. While this is still mostly true, Orion’s little XT4.5 breaks the price barrier in a big way. As long as you can deal with the short eyepiece height, it’s a great starter scope.

Orion SkyView Pro 127 GoTo Mak-Cass Telescope
Here’s a telescope for the enthusiast who appreciates the practicality of a compact scope, yet wants the best features and performance available for the money. The Orion SkyView Pro 127 GoTo Mak-Cass Telescope comes with fully motorized GoTo computer control! After a simple alignment, a push of a button or two on the GoTo hand controller automatically points the telescope to one of 13,400+ celestial objects in its database. Dual stepper motors on the mount slew the telescope at a brisk 3.4° per second, centering your target right in the eyepiece. Easy!

The GoTo system consists of a computerized hand controller and two stepper motors that attach to the SkyView Pro telescope mount. What can you see with your Orion SkyView Pro 127 telescope? With intuitive menus and easy-to-use pushbutton controls, the GoTo system allows you to locate and track any object in its database of 13,400+ celestial objects including the entire Messier and NGC catalogs. You can use the GoTo controller to take a guided tour of the night sky or to pinpoint celestial highlights for the month. The GoTo hand controller requires an external 12-volt power source.

The SkyView Pro (SVP) 127’s high-resolution 5″ optics and 1540mm focal length (f/12.1) excel for high-magnification study of the lunar surface and planets. And it’s got enough aperture to display excellent astroimages of a wide variety of deep-sky jewels. The optical tube assembly is just 14.5″ long, making it wonderfully portable and easy to stow.

The Orion SkyView Pro 127 EQ mount provides fluid motion and a solid stance. 

If you are new to astronomy and aren’t familiar with where things are in the sky, then this is the best telescope for you! And the best part? You get to show others just how much of an astronomy expert you are when you can tell them the name of the object being viewed!

Last of a series

Your telescope

No matter what telescope you select, choose one that will meet your precise needs and interests. The planets, the Moon, and close stars require high power, good contrast, and sharp resolution, and if these are the objects of your attention, a refractor or reflector would be a good choice. Because very faint objects like galaxies and nebulae need a large aperture, you should invest in a big reflector telescope to view these. An all-purpose midrange telescope should serve best, for example a 6″ to 8″ reflector or an 8″ Schmidt-Cassegrain.

Keep checking back. Future articles will delve into filters used to cope with light polluted skies, astrophotography, astronomy book and software reviews, astronomical binoculars, and reviews of specific telescope models.

Welcome back to part 3 of my series on how to buy a telescope.

The reflecting telescope

Reflecting telescopes use a parabolic mirror at the back of the telescope to gather and focus the light to a flat secondary mirror that the image out of an opening at the side of the main tube. You observe through an eyepiece on the side of the tube up near the top.

ﾷ Easy to use
ﾷ Excellent for faint deep sky objects such as remote galaxies, nebulae and star clusters because their larger apertures collects more light
ﾷ Low in optical irregularities and deliver very bright images
ﾷ Reasonably compact and portable
ﾷ A reflector costs the least per inch of aperture compared to refractors and catadioptrics

Disadvantages

ﾷ Not suited for terrestrial applications
ﾷ Slight light loss due to secondary obstruction when compared with refractors
ﾷ The tube is open to the air, which means dust on the optics even if the tube is kept under wraps

Check back often for the continuation of my series on how to buy a telescope. Part 4 will discuss catadioptric telescopes.

Part two in my series on buying a telescope

In part one, I discussed why aperture is important in choosing a good telescope and also about telescope power. As I continue my series, I will discuss the refracting telescope. Be sure to check back for part 3 on reflecting telescopes!

The refracting telescope

Refracting telescope are the most common form of the telescope – a long tube where light passes directly from the front objective lens directly to the eyepiece at the opposite end of the tube.

Advantages
ﾷ Easy to use  due to the simplicity of design.
ﾷ Good for distant terrestrial viewing
ﾷ Excellent for lunar, planetary and binary stargazing especially with larger apertures
ﾷ Sealed tube protects optics and reduces image degrading air currents
ﾷ Rugged, need little or no maintenance

Disadvantages
ﾷ Generally have small apertures, typically 3 to 5 inches
ﾷ Less suited for viewing small and faint deep sky objects such as distant galaxies and nebulae
ﾷ Heavier, longer and bulkier than equivalent aperture reflectors and catadioptrics
ﾷ Limited practical usefulness
ﾷ Good-quality refractors cost more per inch of aperture than any other kind of telescope.

Buying a new telescope can be confusing, especially for the first timer. Many are left wondering which telescope to get. Understanding telescopes and their various accessories can go a long way in choosing the best one for you. Whether you are a beginner or old pro, in this first of a six part series, I will help you better identify the different types of telescopes and help you find the best telescope for you.

Aperture of a telescope

A telescope’s singular most important attribute is its aperture. Aperture is a measure of a telescope’s light gathering ability and determines the brightness and sharpness of everything viewed through your scope. Aperture is the diameter of the main lens or mirror and as the aperture increases so does the details of the image you see. A good 10″ aperture scope shows sharper images than even a well-made 6″ aperture telescope.

Since aperture is so important, many astronomers are misled into believing that getting the biggest aperture you can afford is the simplest way to choosing the best telescope for you. This isn’t always the case. If you make your decision based solely on the size of aperture, you might end up owning a big telescope that sits unused.

Where will you use your new telescope? If  nearby in the backyard then having a large telescope will be of advantage to you. If you need to carry the telescope to to an observing site away from city lights, you will definitely need something compact, yet powerful. Don’t forget that you may have to assemble and set up your telescope in the dark. A scope that is too big to carry outdoors and too difficult to set up just won’t get used.

Telescope Power

Power and design, like aperture, are other important considerations when deciding which telescope to purchase. Power is a critical factor since it determines how close a view you can get of space objects such as planets but it is not a decision making factor. You can control the  power by using different eyepieces.

An eyepiece is the small removable lens assembly you look into. Most telescopes come with several eyepieces and you can buy more separately. Remember to match the power of your eyepiece lens with the aperture of your scope for clear images. The lowest powers are the easiest to use, especially for beginners, and provide the most pleasant views.

Telescope Designs

Even among telescopes with the same aperture, some designs are more portable, others give sharper images while still others are more economical. There are three basic kinds of telescope to choose from depending on your specific requirements.

ﾷ Reflecting telescope,

ﾷ Refracting telescope, and

ﾷ Catadioptric telescope.
Despite their differences in size these 3 telescope types have the same light-gathering properties. They also have a similar purpose, to collect light and bring it to a point so it can be magnified and examined with an eyepiece, but each does it differently. Therefore, each type of telescope has its pros and cons, which you can match with your observing needs.

Come back soon for part 2 of this article when I will discuss refracting telescopes!