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Introduction to Astrophotography. Blythe Guvenen Kitt Peak Visitor Center. Astrophotography.

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introduction to astrophotography

Introduction to Astrophotography

Blythe Guvenen

Kitt Peak Visitor Center

astrophotography
Astrophotography
  • Astrophotography is a specialized type of photography that involves making photographs of astronomical objects in the night sky such as planets, stars, and deep sky objects such as star clusters and galaxies.
astrophotography1
Astrophotography
  • Astrophotography is used to reveal objects that are too faint to observe with the naked eye.
  • Digital cameras
    • Can accumulate and sum photons over long periods of time.
  • Astrophotography poses challenges that are distinct from normal photography.
    • Subjects are usually quite faint, and are often small in angular size.
daguerreotype
Daguerreotype
  • First photographic plate, thin film of polished silver on a copper base.
  • Invented by Louis Daguerre in 1838
early astrophotography henry draper
Early Astrophotography!Henry Draper
  • First to photograph the Orion Nebula; September 30th, 1880
  • 50 minute exposure!
the human eye
The Human Eye
  • No permanent record of images.
  • No way to change exposure time.
  • No good way to measure quantitatively.
to film or not to film
To film or not to film?
  • Pros:
    • Well-established
    • Archival quality (black and white)
  • Cons:
    • Finicky to temperature, humidity, processing conditions
    • Fragile; brittle
    • Low efficiency: 1-10%
    • Non-linear (reciprocity failure)
    • Difficult to get quantitative information
    • Nearly extinct!
charge coupled device ccd
Charge Coupled Device (CCD)
  • Semi-conductor based solid state detectors
  • Incoming photons generate electrons that are added up to form an image
  • Excellent quantum efficiency: 60-90+%!
  • Available for a wide range of wavelengths:
    • 300 - 1100 nm (Si)
    • 1 - 5 µm (InSb)
    • 1 - 25 µm (HgCdTe)
astrophotography using a camera
Astrophotography Using a Camera
  • Good quality, wide-angle photographs of the night sky can be made by almost anyone using a single lens reflex digital cameras.
  • Should travel far away from the bright, light-polluted skies.
    • Prevent the photograph from being completely washed out and ruined by bright urban light pollution.
fixed position mounting
Fixed-Position Mounting
  • Equipment needed
    • Camera capable of long (>30 sec) exposures
    • Sturdy tripod
  • Techniques
    • Amount of trailing depends on exposure time and declination
    • Digital stacking
    • Time-lapse
tracked wide angle shots
Tracked Wide Angle Shots
  • Equipment
    • >30 second exposures
    • Tracking mount
    • Piggybacked camera w/ lens
  • Techniques
    • Digital stacking
    • Foreground will trail (unless you use a flash to freeze it)
short exposure astrophotography
Short Exposure Astrophotography
  • Use CCD with “Hyperstar” or modified webcam
  • Short exposures = less expensive mount
    • Align and stack
    • Exact polar alignment is less important
    • Larger periodic error is tolerable
    • Unguided
long exposure astrophotography
Long Exposure Astrophotography
  • Good mounting is critical
    • Exact polar alignment is necessary
    • Solid connections (rings, plates, etc.)
  • Must be guided
    • Manual or auto
    • Need reticle EP or autoguider
long exposure astrophotography1
Long Exposure Astrophotography
  • Guiding
    • Piggyback
      • Need adjustable rings
      • Need larger mount
      • Differential flexure
    • Off axis guider
      • Can be hard to acquire guide star
    • Built in autoguider
      • Guides through filter  less sensitivity
astrophotography using a telescope
Astrophotography Using a Telescope
  • Afocal
  • “Prime” focus
  • Eyepiece projection
  • “Piggyback”
afocal photography
Afocal Photography
  • Simplest telescope coupling (unguided)

- Skylight filter recommended (protect camera lens)

  • Difficult alignment and focussing
  • Variable results - lots of patience!
  • Good telescope method to start with

- Digital cameras

  • Requires good quality eyepiece
prime focus
“Prime” Focus
  • Camera directly coupled to telescope
  • Telescope objective acts as very long focus lens
  • Camera replaces telescope eyepiece
  • Focusing easier than afocal method
  • Telescope guiding desirable!
prime focus1
“Prime” Focus

Cassegrain telescope

Off-axis guider

Focus on chip

Detector

Camera

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