Eyepieces Used By Questar

Eyepieces from 1950 to Present

Erfle 1950 to 1968

Questar has used several types throughout its history. Early Questars used what we call "Erfle" eyepieces. They were made in Japan. They had a more rounded shape on the top and generally were marked 40-80 and 80-160. Sometimes they had an X after the numbers. This number closly follows the amplifying power generated by the eyepiece when used with the Questar telescope. They also had a knurled (ridged) area near the top so the user could rotate it to focus the finder. This type of eyepiece was used until the late 1960"s and was replaced by the Brandon eyepiece. As far as its design type, we are really not sure if it was a true Erfle but in the early years, an eyepiece was just an eyepiece. Classification of designs had not really begun. By today’s standards it is closer to a Plossel but it had the ability to zoom ( move the internal elements in relationship to each other). The 80-160 had four elements while the 40-80 had five. The AFOVs is approximately 50° to 60° and they are wider than the Brandon which is 45°to 50°.

Early Brandon 1968 to 1972

Early Brandon eyepieces had a curved shape similar to the Erfle top but did not have a built-in focuser and were made in the USA. The Questar had to have a diopter adapter focuser installed into the top port. Then the eyepiece was screwed into it to allow for finder focus. The 1/2" area below the thread was 1-1/4 Ø and could be used with a slip-fit telescope. This change was made in the late 1960’s and early 1970’s. The Brandon eyepiece design is its own design type but is similar to todays Plossel (4 elements) design. It has very good optical characteristics and is ideally suited for the Questar high power and resolution optical design. It doesn't have the FOV of today’s wide and super wide eyepiece designs but it's simplisity makes it a great choice when you want to maximize the resolving power of the Questar telescope.

Current Questar - Brandon 1972 to 1980, 1983 to date

Current Brandon’s have changed in shape but have the same basic optical design. A thread on rubber eyecup was installed. There has been some minor variation of thread size. To our knowledge the eyecup has always screwed off but on later Questars it can be pulled off the plastic threaded insert. It may also be folded down for ease of viewing when wearing eye glasses. Early units had the eyecup molded onto a metal threaded insert and could not be pulled off. This eyepiece also had to use the diopter adapter focuser.

Questar 1979 to 1983

For a very short time Questar manufactured its own eyepieces designed specifically and optimized for the Questar telescope. These eyepieces looked identical to the Brandon with two exceptions: the rubber eyecup does not thread on and it is engraved " Questar " only. The eyecup pulls off and has a groove that it snaps onto. These eyepieces were only made for a few years and are rare!

Eyepiece Diopter Adapter 1995 to date

The Questar eyepiece diopter adapter was introduced with the Questar-Brandon type eyepieces in 1970. It has remained unchanged until 1995 when two locking thumbscrews were added for the use of non Questar standard eyepieces. This change allowed the 1-1/4 type eyepiece to be inserted and held in place for use with the Questar. All types of eyepieces can now be attached and used with the Questar telescope but not all of these eyepieces will work effectively. The Questar was designed to be a high power and high-resolution optical system with great internal baffling to increase contrast. Some wide field type eyepieces may not work optimally due to this baffling system. The other problem with most of the 1-1/4 type eyepieces is that the built-in finder system may not be able to focus due to the draw tube length.


Eyepiece types


Early Brandon



Eyepiece Diopter adapter with thumb screw