This class is intended for teens and adults, but children as young as 8 who are interested in telescopes should be able to understand most of it. This class will be held as one 2-hour session. You will need to print Telescopes and Optics Materials.

You may wish to try our Telescopes and Optics Exercises which reinforce your understanding. These are NOT tests and are not scored. If you have problems with them your instructor will try to help you understand.

How Telescopes Work

• Telescopes are easy if you don't look too hard!
• Basic Optics
• Two Tales
• Lenses
• Eyepieces

Binoculars

• Advantages
• Portability!!!
• Frequency of use!!!
• Disadvantages
• Stability
• Limited magnification and light grasp
• Opera Glasses
• Porro prisms
• Roof prisms
• Stabilizers and tripods

Refractors (Dioptrics - objective lens)

• Advantages
• Sturdy sealed tubes
• No objective obstruction
• Ease of alignment
• Disadvantages
• Long Tube
• Chromatic Distortion - particularly at short focal lengths
• Expensive relatively
• Modest eyepiece wandering
• Wobbly
• Spotting scopes
• Inverting scopes

Reflectors (Catoptrics - objective mirrors)

• Advantages
• Free of chromatic distortion
• Cheapest design versus capacity
• Easiest alignment of all telescopes
• Disadvantages
• Objective obstructed by diagonal
• Defraction caused by spider
• Very wobbly
• Long tube for slow telescopes
• Wandering eyepiece
• Newtonians
• Classic Cassegrains

Catadioptrics (Objective mirror with corrective lens)

• Advantages
• Compact tube
• Least wobbly
• Negligible chromatic distortion
• Eyepiece location
• Sealed Tube
• Disadvantages
• Most expensive design versus aperture
• Objective obstructed by return mirror
• Hardest to align
• Schmidt-Cassegrains
• Maksukovs

Alti-azimuth mounts

• Advantages
• Placed above C. of G.
• Tightest turning radius (azimuth)
• Tightest tilt angle (catadioptrics)
• Strongest design versus weight
• Disadvantages
• Complex 3D motions require special compensating equipment.
  Hand guiding is possible for visual work, but for photography, CCD imaging of dim objects, and any other type of instrumentation, the telescope much be slowly turned in three separate dimensions according to a complex mathematical curve.
• Zenith is obscured to instrumentation (temporary)
• Dobsonians
• Bowling balls
• Swivels
• Yokes

Equatorial mounts

• Advantages
• Simplest system to synchronize with sky - RA clock drive
• Derotation and declination movements are not required
• Disadvantages
• Off center balance (wedge alleviates but does not remove problem)
• Weaker design for a given weight
• Counterweights need to be large for German mounts
• Off center pier placement
• Large turning circle in RA
• North pole obscured permanently
• 360^O circles invert image in some designs
• German mounts
• English Yokes
• Open yokes and wedges

Automation versus manual operations

• Star hopping, long may it live
• GOTO telescopes
• PCs, and Planetarium Programs

Specialty Telescopes

• Hubble Space Telescope versus Keck and Cerro Paranal
• Radio Telescopy
• Great Parboloids
• Arrays and Interfrometry
• Long Base Line
• Project SETI
• Infra Red Telescopy and Moisture
• Ultra Violet Telescopy and Interstellar Medium
• X-ray and Gamma Ray Incident Angle telescopy

Department store telescopes

• Aperture
• Magnification
• Quality
• El Cheapo eyepieces
• Gimcracks and doodads
• GOTO refractors
• Highlighting the good features
• Try a better eyepiece
• Put the scope on a decent tripod
• Disconnect useless doodads
• Don't crush a kid's hopes

Purchasing your first telescope

Dangerous Frauds and Disasters