Announcements:

1
Lab 2

• Announcements
• Simple numerical error analysis procedure on the
  website
• Office hours changing
• Monday 130-230
• Wednesday 130-230

2
Lab 1 Grade Distribution

• Average (without zeros)71
• Average (with zeros)59

3
Telescopes

• We use telescopes to magnify distant objects
• There are two major types of telescopes
• Refractors use lenses
• Reflectors use mirrors
• Many modern telescopes are a hybrid of the two
• Our telescopes are primarily reflectors, but have
  a corrector plate (big lens) on the front

4
Magnification

• The magnification is determined by the focal
  lengths of the telescope and eyepiece.
  (Mftelescope/feyepiece)?
• Focal length is the distance between the
  lens/mirror and where an object coming from
  infinity is focused
• This is why many telescopes are long
• Reflectors advantageous here can fit a longer
  focal length inside a smaller region
• Can you have too much magnification?

5
Too Much Magnification

• Its tempting to zoom in as much as possible, but
  everything has limits
• More magnification makes image dimmer
• Light spread over a larger area
• You not only magnify your target, but everything
  in between as well (atmosphere)?

6
Brighter Images

• Most of what we look at through telescopes are
  far away and dim
• We want to make our images bright!
• How do we get brighter images ? collect more
  light ? make telescope wider
• Refractors at a disadvantage can only be so
  wide
• Some times this is not enough
• Many images are long exposures
• Hubble Ultra Deep Field (11 days-worth of light
  collecting!!!)?

7
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8
Celestial Coordinate Systems

• Right Ascension and Declination (RA/DEC)?
• Units?
• Why is it advantageous over other systems like
  latitude and longitude?

9
And now tonights lab

• Well be measuring field of view of our telescope
  (angular size seen through the telescope)?
• Primary Method timing of stars crossing the
  field of view
• Can do this because the Earth rotates at a
  constant speed (15 degrees per hour)?
• Time with a velocity gives a distance
• In case of clouds
• Can put the telescope into a rough
  alignment--gtturns on the tracking motor
• Look at a stationary object, moves like a star in
  the sky--gtmimics the original process

10
Procedural Notes

• Measure FOV crossing time at least 3 times and
  take an average.
• Don't forget to find theoretical field of view
  and compare it to your measured field of view.
• You'll need a couple of specs for the telescope
  and eyepiece see the handout
• Mind your units!
• q(degrees)15(degrees/hour) x t(hours)?
• q(arcminutes)15(arcminutes/minute) x t(minutes)?
• q(arcseconds)15(arcseconds/second) x t(seconds)?