Beginner Telescopes

1
Beginner Telescopes

• How to get something that will not live in your
  closet

Rob Hawley SJAA Beginner Workshop Aug 07
2
Agenda

• Technology of Optics
• Type of Mount
• Electronics
• Good Buys / Bad Buys
• So What Should I Buy

The Opinions expressed in this presentation are
of the author and may not reflect the views of
the board of SJAA
3
Goals

• Focuses on starter Scope
• Likely will be replaced
• The less you spend the more likely true
• Get you a scope you will be happy with
• Warning Authors Opinion
• Caveat Emptor

4
Important Telescope Terms

• Diameter
• Larger means dimmer objects
• Focal Length
• How much potential magnification
• 400mm low mag, 900mm more mag
• More on this next month
• F Ratio
• Focal Length Diameter x f ratio
• Mount

5
Magnification Claims

• Small scopes frequently have outrageous claims.
• Reality for excellent optics is
• 50 x Objective Diameter(in inches) Max
• Cheaper Scopes probably half this or less
• Magnification is Poor Measurement
• Come Next Month

6
Technology of Optics
7
Refractor

• Straight Tube with lens at front
• achromatic expect color halos
• No need to adjust
• Good for planets iff good optics high f
• Wide Field if f 5

8
Reflector

• Design By Isaac Newton
• Requires some adjustment
• Usually good value for money
• Commonly uses Dobsonian Mount

9
Cassegrain (Mak/Cas)

• Folded Optical Path
• Higher F ratio in smaller package
• Combination of Lens and Mirrors
• Convex Lens
• Typical Small (3 - 7)
• Good Planet Scope

10
Schmidt Cassegrain (SCT)

• Different Arraignment of Lens and Mirrors
• Larger Diameters than Mak/ Cas
• Go To Built In
• Heavy
• Expensive
• Cooling Problems

11
Each Scope Has Its Niche
12
Types of Mounts
13
Alt Az

• Simple Mount 2 adjustments
• Think Camera Tripod
• Does not track
• Easy to Use

14
Dobsonian

• Alt Az mount with pivot at bottom
• Inexpensive
• Easy to use

15
GEM

• German Equatorial Mount
• Aligned with sky
• Single Adjustment tracks objects
• Motors cheaply added
• Not Recommended for Beginner
• Requires rotation for different parts of sky
• Counterweights
• North Alignment

16
Fork (SCT)

• Adds a lot of weight
• Alt Az
• Electronics handle tracking
• Generally Stable

17
Electronics

• Helps Track, Find, and/or GO TO Objects
• Adding Tracking on GEM is cheap
• Find is more expensive (GEM, Dob)
• Digital Setting Circles (DSC)
• GoTo is expensive
• SCTs have GoTo built in

18
Dont Rush to the Store

• Come to Star Parties
• Learn what you want to look at
• Watch as Objects Located
• Refractors may have eyepiece very low or high
• Reflectors require bending over tube
• See which views look good to you

19
Good Buys / Bad Buys

• Including only credible first scope choices
• Are you willing to buy a starter scope?
• Price Ranges
• lt 150
• 150-299
• 300-500
• gt500

20
Scopes Less than 150

• Dime store scope
• Small aperture refractor
• Poor quality optics
• Rickety mount
• gt Most Likely to just Fill Your Closet

21
150 - 299

• Orion StarBlaster - 179
• Well liked by Sky and Telescope
• Wide Field (fl 450mm, dia 114mm)
• Orion 6" Dob 269
• Smallest big scope reflector
• Much better than dime store scopes
• Likely to outgrow

22
300-500

• 102 mm Orion Mak Cas on Alt Az 300
• Very Compact, High Magnification
• 80 mm Orion ST80 on GEM 300
• Compact Wide Field Scope
• 8 Dob (Orion, Celestron)- 369
• Good to Excellent Optics
• May use for many years
• Vixen - A80MF - 80mm f/11.4 Alt Az - 439
• Minus V Filter will improve

23
More Than 500

• Many More Choices Available
• Credible Long Term Choices
• Probably more than you should Spend Now
• If you Really demand Electronics
• DSC System
• 6 Orion Intelliscope 499

24
So What Should I Buy

• What do you want to look at?
• Big OC gt wide field
• Galaxies gt large aperture
• Planets gt high f ratio refractor or Mak/Cas
• Cheaper scopes will likely be replaced
• GEMs complex to setup and use
• But they can track

25
Next Month - Eyepieces

• The rest of the Telescope