Types of Telescopes and MountsTelescopes: Refractor Reflector

(Newtonian)Catadioptric

(Schmidt-Cassegrain)Advantages • Simple- thus easy and

reliable• Good for close objects

(Moon, planets, double stars)• Closed tube– not affected by dew inside.

• Little maintenance.

• Made of fiberglass or cardboard tube and mirrors. Easy to make = Cheap per inch!

• Relatively compact• Good for distant, deep

sky objects• Overall fewer optical

aberrations.

• Has both lenses and mirrors so many disadvantages of other ʻscopes are canceled.

• Short barrel- more portable.

• Good for both deep sky and close objects.

• Closed tube – not affected by dew inside.

Disadvantages • Made of metal and lenses. Harder to make = More expensive per inch

• Lots of cheap bad ones around

• Not suited for deep sky objects(nebulas, star clusters, galaxies)

• heavier, longer and bulkier

• Some color aberration

• Open tube: -air currents and dew

can enter the telescope

• Often mirror aberration (off-axis coma)

• not preferred for close stuff

• eyepiece set high up. Larger telescopes need a stepladder!

• Made of metal, mirrors and lenses. Harder to make

= More expensive.

• Short-barreled and funny-looking. Newcomers are put off from buying due to unusual appearance.

Mounts: Altitude-Azimuth(most common type is Dobsonian)

Equatorial mount

Explanation: Moves on a pivot anywhere to any altitude or azimuth

Pivot pointed north so scope is aligned with the earthʼs axis. Moves N-S and E-W. has circles measured in degrees for Declination and R.A.

Advantages • Simple! • Once aligned it is very easy to keep objects in view (less maneuvering)

• Can add clockwork to adjust automatically -no work! (it can be computerized to go to

any programmed star)Disadvantages • Hard to keep objects in view

(have to keep adjusting every few minutes!)

• Fiddly to set up• Often harder to transport