A Good Entry-Level Telescope

Keep the telescope. Throw away the mount and tripod. Keep the eyepieces as curios for historical reference. The average beginner telescope costs about $159 whether from Orion, Celestron, or Explore Scientific. For that money, 70% of the value is in the optical tube assembly (OTA: the telescope itself) another 20% is in the useless junk that goes with it and then 10% is lost to packaging, instructions, and perhaps extras such as star charts. So, what does it take to build a good entry-level telescope?

 

Start with the Mount.

Just as the scabbard called “Avalon” was more powerful than “Excalibur” (the blade it sheathed), the positioning mechanism (“mount”) is more important than the telescope. 

 

The best entry-level mount and tripod that I have is the Explore Scientific First Light Twilight Altitude-Azimuth with slow-motion controls. It costs $349.99. I use it for my ES 102-mm f/6.47 refract0r, my Astronomers Without Borders 130-mm Newtonian, and all of my 70-mm refractors. 

 

I found that the Orion VersaGo E-Series Altitude-Azimuth mount—rated for 11 lbs (5 kg)—is sufficient for the 70-mm refractors. It retails for $99.95 and is currently marked down from Orion at $89.99, which indicates to me that this will be discontinued. I bought four of them, one for each of the 70-mm scopes that I will sell and another for the one that I will keep. It also can carry the AWB 130mm Newtonian which weighs only 5 lbs (2.3 kg).

Orion VersaGo E-Series Mount is $100.

 It is not perfect. The gearing does have sloppy “backlash.” You have to turn the slow-motion controls several twists for them to engage in any direction. Even so, it is better than every other competitor. 

 

Previously reviewed here, 70-mm refractors from 
Bresser, Meade/Orion, and Celestron.

The original Meade alt-az mount did not work at all in left-right azimuth, no matter what the tensioning. The Bresser German Equatorial mount likewise failed to provide even crude adjustment. The Celestron movie camera pan-tilt mount was cheap plastic incapable of any smooth motion. So, for the money, the Orion VersaGo does let you have good control of the viewing field, left-right and up-down.

All Tubes are Created Equal.

Just as we are different individuals who are equal under law, so, too, are these telescopes somewhat different but essentially equivalent. The optics are a given. It is for this reason that Sky & Telescope's  Gary Seronik is a fan of cheap binoculars: the expense is in the gears, not the glass. (See Binocular Highlights reviewed here.)

 

The Celestron 70-mm AstroMaster has a longer focal length: 900 mm or a ratio of f/13. So, it offers more magnification with a given “eyepiece” (ocular). It is important not to be seduced by useless magnification advertised in bright colors on the box of a department store telescope. In her guide, Celestial Sampler, Sue French (a Sky & Telescope columnist), typically views with her 4-inch telescope at 47X. 

 

However 900/12.4 > 72 and 900/32 > 28 and a 2X Barlow will double the larger to modest but sufficient 144X. Those numbers are not importantly different from the magnifications of the competitors. 

The Orion and Bresser are both f/10 telescopes, focal lengths of 700 mm. And the oculars will render images at 56X and 21X (doubled to 113 and a convenient 43X). 

 

Moreover, with a refractor (though not with a Newtonian) you can place a 2X Barlow ahead of the diagonal rather than after it and in so doing enjoy a 3X magnification. Personally, I experienced that observing technique and it can be inspiring if not overly more informative. It does offer mid-range options for 65X or 84X. 

It is a simple fact that different objects viewed under different sky conditions will look somewhat better or worse for marginally more or less magnification. So, you want incremental arrangements.

 

Some Oculars are More Equal than Others.

The Bresser 70-mm Callisto comes with 25 mm and 9.7 mm Plössl oculars (“eyepieces”). These are standard, modern designs, two matched pairs of plano-concave lenses. For want of an umlaut, the name often appears as just Plossl or more correctly Ploessl. Even expensive, complex, computer-driven entry-level telescopes arrive with older ocular designs, called “Modified Achromatic” or “Ramsden Achromatic” or “Modified Kellner”, all of which are three-lens arrangements. The Celestron AstroMaster comes with two Kellner oculars, 20mm and 10mm. The Meade StarPro comes with three Kellner eyepieces, 26 mm, 9 mm, and 6.3 mm, and a 2X Barlow lens.
 

·       2020-December-6 Focus on Georg Simon Ploessl 

 

I found better “Super Plössl” eyepieces of focal lengths 32mm (GSO brand) and 12.4mm (Meade 4000 series) to add to the instrument packages. The advantages are better construction: metal barrels, not plastic, blackened inner tubes to eliminate stray reflections, better glass in the lenses and closer specifications in production. 

Better oculars sold by Astronomics (left) 
and Agena Astro Products (right).

Also, the longer focal lengths deliver better “eye relief” a measure of how near or far your own eye must be from the lens to get the best view. With cheaper, smaller lenses you must be uncomfortably close to the eyepiece, with a smaller cone of light, and it is like viewing Grand Canyon through a soda straw. With the wider view of better eye relief, you come close to that very rewarding “walk in space” experience when stargazing.

 

What Can You See With That?

It is an easy generality that most backyard stargazers make the famous “double double” of Epsilon Lyrae the gold standard for performance. I achieved that view with each of these. It depends on the “seeing” the quality of the sky, more than on the aperture of the objective or the magnification of the ocular. Given those parameters, each of these 70-mm refractors at their greatest magnifications will split all four stars into two binaries.

 

Of course, there is more to backyard stargazing than that. Double stars Albireo in Cygnus, Algieba in Leo, Zuben el Genubi in Libra, Graffias in Scorpius, open clusters like Messier 44 the Beehive, and globular clusters such as  Messier 13 in Hercules, as well as Mars, Jupiter, and Saturn and more are all available. 

 

I have been at this for a while, ever since being given my first (adult) telescope for my 65^th birthday in 2014, a Celestron 130-mm Newtonian reflector on a German Equatorial Mount. I  used this blog to gather my thoughts, observations, theories, and opinions.

 

·       2019-December-14 Defending the Hobby-Killer Telescope 

·       2019-December-14 In Support of the Entry-Level Telescope 

·       2021-November-7 70-mm Shootout 

·       2022-May-22 Product Review: Bresser EQ3 and f/10 Refractor 

 

You can find other informed opinions. On the popular discussion boards (Cloudy Nights, Stargazers Lounge, Sky Searchers) every introduction in the Beginner’s Forum that asks “What Should I Buy?” receives an easy 12 to 20 opinions, sometimes running into lengthy arguments between aficionados. The highly regarded Nightwatch: A Practical Guide to Viewing the Universe  by Terence Dickinson (revised fourth edition, 2019) recommends a 6-inch Dobsonian as the ideal beginner scope. It offers a large aperture, is easy to collimate–align the mirrors; a requirement of frequent maintenance for any Newtonian–and with a base of 25 lbs (11 kg) and a tube of 15 lbs is easy to carry in two pieces.

The true costs of a decent beginner telescope
(Don't forget shipping and taxes.)

 

That all being true, a smaller refractor comes to ambient temperature quicker than the tube of a Dobsonian. Until you reach temperature, you will be viewing through a column of shimmering air in the tube. Also, a larger aperture returns a worse view when the atmosphere itself is turbulent whereas a smaller diameter objective transmits a lower ratio of noise-to-signal.

A refractor requires no collimation. (At least, it is very infrequent and should be done by returning it to the seller for proper work). Also, the 1200 mm tube is a stretch if you want to collimate by looking into the alignment tool while adjusting the back screws. It is not clear to me what you do with the tube when it is not mounted. In other words, the refractors can be set on their Vixen bars without affecting the optics. Can you lay a Dobsonian on its side? You do not want to stand it on its mirror. If you stand it on the opening, is it stable? And once set up, how easy is it to move that 1200 mm (four feet long) 50 lbs tube on its box mount? 

 

Currently $460 from Astronomics, 
and several others.

I agree that the 6-inch Dobsonian is a great telescope, all in all. No telescope is perfect. I selected the 70-mm refractor for portability and range of targets based on frequent and easy backyard viewing. 

 

PREVIOUSLY ON NECESSARY FACTS

The Origins of Technical Writing 

Readability is the Only Metric 

Visualizing Complex Data 

An Objective Philosophy of Science