Advice Telescopes

A replica of a telescope attributed to Galileo.

All About Telescopes

Choosing a first telescope can be daunting.

MY RECOMMENDATION for a first choice telescope is ONE of the following three types of telescopes:

a) 3 or 4-inch Refractor
b) 6 or 8 inch Newtonian Teflector (Dobsonian type)
c) 6 or 8 inch SCT (Schmidt-Cassegrain Telescope).

Notes
1) Make sure the mount and tripod are robust for steady viewing.
2) Most people who stay in the hobby will have owned several telescopes.
3) The telescopes sold at the end of the year at Costco and other stores are NO GOOD! You will be turned off with astronomy using them.
4) Oh, you will have to purchase extra eyepieces to change the magnification. See the info about eyepieces in my TOP PICKS.

Illustrated
Dictionary
of Terms
about
Telescopes,
Optics
&
Mounts

I do not receive any type of compensation for my recommendations.

Read more about these telescopes below and my TOP PICKS.

Refractor Telescopes

When most people think of a planet, they think of Saturn. When they think of a telescope, they think of a refractor. A refractor is a telescope with a front lens that brings light to a focus at the rear of the instrument.

Refractors were the first telescopes. It all started around 1608 when Galileo and other scientists heard about the invention and made their own instruments for astronomical use.

Refractors were used extensively by astronomers until the early 1900s, when they were replaced by reflectors that were larger and less costly to build. The largest refractor in the world, completed in 1897, is the 40-inch diameter Yerkes refractor at Williams Bay, Wisconsin.

Among amateurs, refractors have enjoyed a resurgence because their optical quality has improved dramatically over the past years.

The Refractor Attraction Refractors are easy to use and practically maintenance free. Unless severely jarred, the optics may never need alignment. The only maintenance is an occasional cleaning of the outside front objective. Today, the tubes are physically shorter than they used to be, which makes these telescopes easier than ever to set up, use and store.

A typical look for a refractor. However, this 4-inch diameter Tele Vue refractor is very expensive because of the exceptional optical quality. This refractor is on a very simple mount—the mount is manual and it is not motorized.

Refractors are often the telescope of choice for astrophotography. Beautiful celestial photos can be taken with refractors having a diameter as little as 2.4 inches.

The Down Side
Refractors are great instruments to explore the heavens, but unfortunately, inexpensive refractors have done more to taint first impressions of observational astronomy than almost any other factor. I have heard, firsthand, numerous reports of disappointment from people who purchased refractors from department stores, or purchased a lower line name brand model.

The irony and “up side” to all this is that middle-of-the-line refractors perform better than ever and the top-of-the-line perform the best of any telescope.

Cost, Objectives and Size Limitations
Per aperture inch, a quality refractor costs more than any other type of telescope. For example, for $3,000, you could purchase either a 4-inch quality refractor (without mount), a 15-inch Newtonian reflector (with mount) or an 11-inch
GO TO SCT (with mount, and read more about GO TO in the discussion on SCT telescopes farther below). Although $3,000 dollars is a lot of money for a quality 4-inch refractor, a middle-of-the-line, good-quality, 3-inch refractor can be purchased for $400 to $1,000. The $3,000 refractor represents the highest quality type and is known as an APO (pronounced A-P-O, an abbreviation for apochromatic, which means “free of any optical aberrations”). These telescopes provide incredibly sharp images.

The largest readily available diameter for refractors is 4 inches (100mm). Diameters of just 5 to 6 inches must often be special ordered, sometimes with waiting periods of several years.

2024
TOP PICK
Refractor

Vixen Telescope
MOBILE PORTA A70Lf

2.75 inch diameter.
Manual mount.
About $500

Available from several
online stores.

Remember, you will need to purchase several eyepieces to change the magnification. I recommend the SVBony line shown below and available from AMAZON. You can purchase the set or buy individually.

Newtonian Reflector Telescopes
Some Newtonian Reflectors are refered to as Dobsonians

The Newtonian reflector has been a workhorse for both professionals and amateurs since its invention in 1668 by Isaac Newton. This type of telescope has a concave parabolic mirror at the rear of its tube that focuses light to an eyepiece near the front end. Amateurs enjoy using reflectors more than ever, in diameters ranging from 4 to more than 36 inches.

Least Expensive
per Optical Inch
The Newtonian reflector is the least expensive telescope per aperture inch. Generally, this telescope is set on a simple, non-motorized mount, called an alt-az mount (short for altitude-azimuth), which moves up and down and rotates to any compass point, similar to binocular mounts at tourist attractions. The optics for reflectors with diameters of 10 inches or less are usually housed in tubes, while those with diameters of 12 inches or more are often placed in an open-frame, truss-tube assembly that can be disassembled and stored compactly (see pictures to the right). As of 2024, an 8-inch Newtonian sells for about $650, a 10-inch for around $900.

A little More Maintenance The Newtonian reflector requires occasional to frequent optical alignments, and occasional cleaning of its mirrors. Aligning or collimating the mirrors is easy to perform after you have done it a few times and there are specialty “tools” to aid in the process. Collimation must be performed after each assembly of truss-tube reflectors. The mirrors of reflectors need occasional cleaning. Depending on storage, use and environmental conditions, yearly cleanings (or much longer intervals) may be all that’s needed. Don’t worry about some dust on the mirrors, which is normal and does not affect viewing. About every 10 to 20 years, the reflective coating may need to be replaced.

This Newtonian Reflector, as shown, with its simple manual mount, is often called a Dobsonian Telescope.

A Dobsonian telescope is nothing more than a Newtonian Reflector on a simple altitude-azimuth mount. In the 1970s, John Dobson popularized simplicty in telescopes in order to make inexpenisve, big telescopes that could be used to introduce the general public to the night sky. I made the one pictured here—I bought all the parts and put it together. However, it is MUCH cheaper to purchase a completed telescope!

A Truss-tube Dobsonian.

Light Buckets
The largest refractors are about 6 inches in diameter, compared to 14 to 16 inches for SCTs, but the largest reflectors zoom to 36 inches or more. Large diameter Newtonian reflectors provide the brightest images of galaxies and nebulae because they collect more light (hence the term “light bucket”) than their smaller counterparts. Image brightness depends on the surface area of the lens or mirror. A 20-inch-diameter Newtonian gathers over 11 times more light than a 6-inch lens or mirror.

Manual Labor
Today, more than ever before, Newtonian reflectors are set on simple, non-motorized mounts. This can be a boon or a bane depending on your orientation and intentions. These simple mounts have allowed manufacturers to hold down costs, enabling amateurs to afford the largest diameter telescopes ever. However, these telescopes are limited to visual use only and cannot effectively be used for astrophotography. Although it is possible to buy a mechanism that will allow these telescopes to follow celestial objects for short periods of time, for the most part these Dobsonian type telescopes are manual and must be continually nudged to keep an object in view.

A little Help from a Friend Newtonians mounted on simple alt-az mounts can be equipped with “encoders” and a hand controller to help find celestial objects. This allows the telescope to work similarly to the GO TO telescopes described below in the next section about SCT telescopes. The only difference is that you move the telescope by hand, watching directional arrows on the hand-controller’s display. Once installed, these systems do work well.

The Telrad
It is not easy to aim a telescope without some optical aid. Traditionally and still in use are little telescopes called Finderscopes that have a wide field of view and sometimes a reticle. However, these are not easy to use. Many Dobs are sold with finderscopes but most amateurs will replace them with a Telrad that provides an illuminated bullseye and no magnification—they are GREAT!

2024
TOP PICK
Reflector

Sky-Watcher
Classic 150P

Dobsonian-type
Newtonian Reflector

6-inch diameter.
Manual mount.
About $500
($350 on sale)

Available from several
online stores.

Remember, you will need to purchase several eyepieces to change the magnification. I recommend the SVBony line shown below and available from AMAZON. You can purchase the set or buy individually.

The only change I would make to this telescope is to replace the little finder telescope next to the eyepiece focuser with a Telrad reflex finder as shown below. See more in left column.

Schmidt Cassegrain Telescopes (SCT)

Biggest Bang for the Buck

The Schmidt-Cassegrain Telescope (often called
S-C-T) is a telescope of choice amongst amateurs, but what is it? Schmidt-Cassegrain is the name of an optical design inspired by Barnard Schmidt (1879–1935) and Guillaume Cassegrain (1625–1712). This type of telescope is often referred to as a hybrid because it contains elements of both reflecting and refracting telescopes. Like a Newtonian reflector, it has a rear primary mirror that focuses light, but it also incorporates a front lens or corrector plate that not only seals the tube from the environment but also helps to fold the optics, making this telescope very compact. The eyepiece holder is at the end of the tube, similarly to a refractor, but for the focused light to get there, it must pass through a hole in the middle of the mirror. This design has been so successful that a 5.5-inch diameter version made by Celestron has been used on Space Shuttle missions.

Computer Automated
GO TO Technology
Today, a major attraction of SCTs is that most come with a mount incorporating computerized GO TO technology. This simply means that after you set up the telescope and align it to three bright stars (a five-minute process guided by prompts from a hand controller), the telescope will automatically move to and follow objects chosen from its huge database. These telescopes can even take you on a tour of the night sky, providing sights of the best objects visible from your location.

An 8-inch diameter SCT by Celestron. This model is computerized and motorized. Overall, it is more robust than my TOP PICK but this comes at a higher price, about $2,500.

Other Hybrids
There are several hybrid designs. The most common after the SCT is the Maksutov (sometimes referred to as the Maksutov-Cassegrain or just Mak), designed by the Russian optician Dmitri Maksutov (1896–1964). The SCTs and Maks look similar but the Maks have an actual lens in front, call a meniscus, that is highly concave. Some people prefer this design because it performs optically a little better than SCTs. Maks are readily available in diameters of 3 to 4 inches. It is rarer to see them larger than this.

Explore Scientific 4-inch Mak-Cassegrain on a nice German Equatorial mount—$400 (2024)

The TERM
GO TO or
GOTO
referes to the ability of a computerized and motorized mount to “find” and follow any object chosen from a hand controller. This type of mount IS NOT specific to SCT telescopes.

Front of an SCT

Why are SCTs the Telescopes of Choice amongst Amateurs?
Simply because they offer the most features for your money. Manufacturers generally sell SCTs as turnkey systems, meaning that they include everything—the telescope on a computerized mount, the tripod, a finder and an eyepiece (you will have to purchase more eyepieces). And, SCTs break down and store well. An 8-inch can easily be packed and hidden in a closet. The 8-inch is the most popular size and sells for about $1,500. I highly recommend this type of telescope if you can afford it.

Maintenance
For the most part, maintenance on SCTs and Maksutovs is minimal. Occasionally, the outside front element should be cleaned but this may only be every few years or even longer, depending on use.

2024
TOP PICK
SCT

NEXSTAR 6SE Computerized
Telescope

6-inch diameter shown.
About $1,000

8-inch diameter is
about $1,500

Available from several
online stores.

Remember, you will need to purchase several eyepieces to change
the magnification. I recommend the SVBony line shown below and available from AMAZON. You can purchase the set or buy individually.

A FEW NOTES
You cannot manually move this telescope by hand—you have to let the motors move it using the hand controller. Also, some, at first, find it confusing to align it to three stars before it can GO TO any object selected from the hand controller which has lists of thousands of objects including the planets, Moon and Sun.

Mounts and Tripods

Basics
Understanding mounts can be just as confusing as understanding telescopes. A good mount and tripod is essential for steady viewing of the night sky—it is a big part of “observing satisfaction.” There is nothing worst than trying to observe with a shaky mount/tripod and since we are dealing with magnifications of 50x and up, this is a very important consideration—especially with the higher magnification of 150x to 300x plus. The mount sits on the tripod (or pedestal or stand). The mount allows movement of the telescope to point to objects in the sky. The tripod elevates the mount so the telescope is at a comfortable height. Generally, inexpensive telescopes aren’t good in the mount/tripod department. There are two basic mounts, the Altitude-Azimuth (Alt-Az) and Equatorial and are described below.

An A ltitude-Azimuth (alt-az) mount on an aluminum tripod. This is a manual mount where you push the telescope up and down for vertical movement and move it in a circle for horizon motion.I would rate this mount and tripod as a solid 5 out of 10 for sturdiness and stability.

A German Equatorial Mount
(abbreviated GEM) on an
aluminum tripod. This type
of mount take a little orientation to get understand its movement. One axis is pointed to the North Celestial Pole (near Polaris). Once accomplished, only have to move the scope on one axis to keep an object in view. This type of mount mimics the motions of the stars in the sky. I rate this mount and tripod as a solid 5 for sturdiness and stability.

The Alt-Az Mount
The altitude-azimuth (alt-az) mount is the basic up-and-down and turn-it-around mount, the same used with binoculars at tourist sites (but you don’t have to insert quarters). This is usually a manual mount and is often found on small refractors and reflectors of around 6-inches or less. A motorized/computerized version is used on the SCT telescopes by Celestron and Meade. The Altitude movement is the up-and-down motion and the Azimuth movement allows horizontal or turning movement to any compass point. Some alt-az mount have knobs on long rods or long springs (long to make the knobs easier to reach) that are turned to help follow celestial objects. The Dobsonian telescopes are all on alt-az mounts and it is possible to motorize these mounts and/or add Digital Setting Circles. Like anything, the quality of alt-az mounts varies, and some work horribly. Usually, the more expensive the telescope, the better quality mount you get, as well as a stable tripod. I have a few manual alt-az mounts that I enjoy using because I can quickly and easily move the scope to objects, of course, using a reflex finder.

The Equatorial Mount
This is a more complicated mount than alt-az mounts (but easy to use) with motorized versions used/needed for amateur astrophotography. Note, there are incredibly worthless equatorial mounts on many cheaper telescopes! This mount has different configurations but the most popular is the German Equatorial Mount (abbreviated as GEM). All equatorial mounts have two axes, perpendicular to each other. One points to the North Celestial Pole (called the Polar or Right Ascension axis) and the other is 90° to it and is called the Declination axis. These axes mirror the Right Ascension and Declination coordinates of the Celestial sphere. Remember, Declination is akin to latitude and Right Ascension is akin to longitude. For this mount to work properly, the Polar axis has to be pointed to the North Celestial Pole (very close to the star Polaris and at the same angle as your latitude). For general observing, this alignment is not critical but careful alignment is important for astrophotography. Equatorial mounts have an adjustment for latitude. One advantage of the equatorial mount is that only one axis has to turn to keep an object in view instead of two for the alt-az. The German equatorial mount is characterized by counterweights to balance the telescope around the Polar axis, so this makes it extra heavy compared to alt-az mounts.

Dobsonian Mounts
Remember, a Dobsonian telescope is nothing more than a Newtonian reflector on a simple alt-az mount. Dobsonians do not have ordinary mounts/ tripods—the mount is in essence the tripod—see pictures above. For many 6, 8 and 10-inch Dobsonians, the mounts are about waist high where they pivot in altitude. Azimuth movement is very close to the ground. On very large Dobsonians, around 15 inches in diameter or larger, the alt-az mounts are very low to the ground and are often referred to as rocker boxes.

Some more about Mounts

Manual, Motorized, GOTO and Digital Setting Circles

Mounts can be manual, motorized, have encoders or motorized/ computerize for GOTO.

Manual mounts. Both alt-az and equatorial mounts can be manual—you move them totally by hand to objects and then nudge them to keep objects in view as the sky turns. Some mounts have what are called slow-motion knobs at the end of short/long rods or springs that are turned slowly to move the telescope, following objects as they move across the sky.

Motorized mounts. Both alt-az and equatorial mounts can be motorized so they automatically follow the path of celestial objects across the sky. No more nudging the scope after you find an object!

A GOTO (pronounced Go To) mount is a motorized/computerized mount that, once set up (aligned using 1 to 3 bright stars), will move to and follow any object selected from its lists of objects using a hand controller. It is available for both alt-az and equatorial mounts. A downfall of GOTO mounts is that once engaged, they cannot be moved manually without losing their alignment but very few people complain about this! Many SCTs can be purchased with alt-az GOTO mounts.

Celestron GOTO SCT showing the hand-controller in an arm of the Alt-Az mount. As with many GOTO mounts, the telescope has to be aligned to a few bright stars using prompts from the hand controller before it can find and follow other objects.

Digital Setting Circles (DSCs) are a hand controller wired to encoders that are attached to the axes of mounts. They aid/allow finding any object in the sky. Digital Setting Circles can be used on alt-az and equatorial mounts and the mounts can be manual or motorized. The hand controller has a very accurate built in clock that can locate any object in the sky after completion of an alignment process to one, two or three stars. Some mounts (telescopes) come with digital setting circles and/or have encoders installed or these might be options. For example, there are digital setting circles kits that are available for Dobsonians. And, I have a motorized GEM that has built in encoders.

How do Digital Setting Circles work on an alt-az mount that does not have motors? The necessary hand controller is basically a computer with an accurate built in clock, databases of celestial objects and prompts/instructions to guide you. The encoders, attached to both axes use thousands of equally spaced marks that are counted as the axes are turned, so this keeps track of position/movement. Initally, the telescope has to be aligned to one, two or three bright stars. Prompts from the hand controller guide you through this process. Once accomplished, the hand controller knows where everything is in the sky and its internal clock keeps pace with the stars moving across the night sky.

Digital Setting Circles (DSCs) is a display/input box that connects via wires to encoders attached to the telescope’s two axes—either Alt-Az or Equatorial. DSCs are meant mainly for manual mounts. After aligning the scope to 1,2 or 3 stars, using prompts form the display, the display will guide you with arrows in pushing the scope to any selected object—planet, cluster, nebula or galaxy.

You can then choose an object (including planets) from the hand controller’s database and watch arrows on the hand controller countdown to zero—your selected object as you move the telescope/mount to the object.

Although digital setting circles are still available, they are becoming less so. In the past, DSCs were a common option on smaller Dobsonian telescopes (6 to 10 inches) but that is not the case anymore. I have an older manual GEM (German Equatorial Mount) that has built in encoders letting me use my DSC, but the tendency today is for mounts to be computerized and motorized, eliminating the DSC hand controller. Additionally, the physical DSC hand controller can be replaced with an App on your phone or tablet.

Setting Circles
NOT DIGITAL

Traditional Setting Circles. Almost every GEM (German Equatorial Mount) has “manual” setting circles on its two axes. Even the cheapest and worthless GEMs have them. In the past, these were used to manually locate objects by dialing in the objects’s coordinates (using RA or Right Ascension which is similar to longitude and Dec or Declination which is similar to latitude). In the very far past, these scales were used to actually determine the coordinates of objects. Although you will find these on GEMs, I do have never used them nor do I know of anyone who uses them, except a good friend who uses them for “fun.”

Many equatorial mounts, including cheap ones, incorporate Setting Circles that are scales which could be used to find objects in the sky using the celestial coordinate system of Right Ascension and Declination but
I know of no one in this day and
age who seriously uses them.

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