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Basic Astrophotography
Dr James West
Twitter: @ejwwest
Flickr: ejwwest
http://www.flickr.com/photos/ejwwest/collections/72157
621948722005/
About me
• Amateur Astronomer
for over 40 years
• Active observer as a
student
• Some
astrophotography with
35mm film
• Active DSLR
astrophotographer for
10 years
• Still at the intermediate
level!
How to capture images like this:
30 minute exposure (6x5 mins) @ ISO 200
And these…
Agenda
• Why photograph astronomical phenomena
• Equipment
• Exposures
• Unguided Camera – Constellations
– Meteors
– Galaxies
– Moon
– Sun
– …..
• Guided Camera
• What can go wrong?
• Further information
Why take astronomical photos?
• The Sky is constantly changing – Professionals can’t watch everything
– Amateurs can discover or monitor comets, novae, variable stars, asteroids and monitor sunspots, planetary changes, lunar phenomena, etc
– Results can be visually impressive and (sometimes) scientifically useful
• For fun and the challenge!
• Impressive results from modest equipment – Digital SLR £250-£3000
– Webcams £50-lots
– Telescopes £200-cost of a car!
– Adapters for iPhones!
Things to photograph
• Moon
• Planets and asteroids
• Sun (with proper protection)
• Comets
• Stars and Constellations
• Deep Sky Objects – Galaxies, Star Clusters, Star remnants
• Eclipses + Transits (lunar, solar, moons of Jupiter)
• Satellites
• Meteors
• Aurora
Equipment
• Any digital camera with: – Manual focussing
– Long exposure settings (preferably “B”)
– Remote release (or timer release) to start and stop exposures without shaking the camera
– A Digital SLR would meet these requirements
• A good tripod
• Optional: – A range of interchangeable lenses for DSLR
• Prices from £50-thousands (or buy 2nd hand)
– Mirror lockup
– Approved Solar Filter for solar use
DSLR Cameras
• Allow interchangeable lenses and direct attachment to
telescopes
• Provide many more features to directly control the
camera and image
• Two main types
– Full Frame (36mmx24mm) Prices £2000 and above
• Canon 1D, 5D, 6D; Nikon FX models
– APS-C ~22mm x15mm Prices £250 to £1500
• Canons 7D and with x0D;x00D;xx00D; Nikon DX Models
• Canon sell the 60Da specifically for astrophotography
– Replaces the IR filter so more sensitive to red light emitted by
Hydrogen in deep space
– Possible to modify other DSLRs but invalidates warranty!
Equipment
Exposures
• Automatic settings on cameras will not deal with very low and extreme light levels – Use Manual Exposure setting
• Need to get as much light onto the sensor as possible
• Exposure length – Must be tripod mounted
– Star trailing on long exposures
• Focal Ratio (f) – lens aperture divided by focal length – Open at widest (but may see aberrations – 1 stop down if so)
– Very fast lenses (< f2) are more expensive
• ISO – increases the sensitivity of the sensor with electronics – More noise at higher ISO as sensor gets hotter
Meteors
10mm f/3.5 ISO 400 213 seconds – Perseids, August 2010
Effects of ISO - 800
ISO - 3200
Lenses
• Any DSLR lens is potentially useful
• Wide Angle (10mm-~40mm)
– Good for long exposure star fields, milky way, meteors,
aurora,ISS
– Most DSLRs come with an 18mm-55mm lens
• “Prime” lens (~50mm)
– Typically faster lenses for shorter exposures and have better
optics (and more expensive)
• Telephoto (100mm-500mm)
– Show more detail
– Star trailing at short exposures (<1sec)
• Zoom lenses give more flexibility and affordability
What’s on when?
• Websites such as Sky and Telescope, Astronomy Now and their magazines give information on forthcoming events
• Heavens-Above and Calsky websites give information on Comets, Satellites and the International Space Station
• Stargazers Lounge, Cloudy Nights websites give “how to” advice and you can upload images
• Local and National Astronomical Societies
Unguided - Scenic snapshots
• Basic method: – Mount camera on tripod
– Switch Image Stabilisation off
– Set on “Manual”
– Set aperture (wide) and ISO
– Point at the sky
– Focus on infinity (sharpest possible image)
– Set the exposure1
– Shoot!
• Many possible targets
• Earth Rotates, so star images move
1 use trial and error or use advice in references
Constellations
50mm f1.4 ISO 800 10s (Sahara) 50mm f1.4 ISO 800 10s (Southampton)
10mm f3.5 ISO 800 176s (Brittany) 10mm f3.5 ISO 200 15mins (Hampshire)
Wide Angle lens
10mm f3.5 ISO 800 30s
Meteors - Perseid 2013
10mm f/3.5 ISO 800 148 seconds – Perseids, August 2013
Galaxies
Satellites/ISS
10mm f3.5 ISO 200 288s 14mm f4 ISO 400 119s
100mm f4.5 ISO 200 47s 10mm f4 ISO 160 210s
Moon
800mm f/11 ISO 200 1/125s 800mm f/11 ISO 400 1/60s
800mm f/11 ISO 800 1/30s 300mm f11 ISO 800 5s (1/250 s moon)
Planets
17mm f4 ISO 200 10s – Mercury, Venus and Jupiter – March 2012
And Comets
Asteroids – Near Earth Objects
DA14
Stack of 30x 10sec exposures
Aurora Borealis
© Greg Little
Eclipses
Exposures of varying length (1/8000s – 1/4s) bring out details in different parts
of the solar atmosphere – 560mm f/8 - China 2008
North Atlantic: Faroes-Svalbard
March 20 2015
Continental USA (Starts Oregon, finishes S Carolina)
August 21 2017
Probably the most accessible eclipse for years
Sun
• Warning: Never photograph or look at the sun without the correct safety filters!
ISS Transiting the Sun Transit of Venus – 2012 http://www.flickr.com/photos/ejwwest/sets/72157623878835436/comments/
Next Transits of Mercury: May 9 2016 and Nov 11 2019
Guided Piggyback – Mount camera on telescope tube
• Need “piggy back” mount for telescope (or
guider mount)
– Compensates for the Earth’s rotation
• Mount camera on telescope
• Use aligned telescope to guide the camera
• Hand or powered guiders can be
constructed using easily available parts
Standalone Guider
http://garyseronik.com/?q=node/52 Various suppliers
Comets
Comet Holmes - 400mm f/5.6 ISO 1600 60s
Comet 2013 R1 Lovejoy
12x 10sec at 400mm, f5.6 ISO 1600
Deep Sky Objects
Orion Nebula - 400mm f/5.6 ISO 1600 30s
Lunar Eclipses
15 second guided. 400mm lens with 2x extender (March 2007 eclipse)
Next Total Lunar Eclipse visible in UK: Sep 28 2015
Lunar Eclipse Sequence
What can go wrong?
• Basic set up: – Camera setting still on automatic (focus, exposure etc) – check
before and after use
– Under/over exposure – try bracketing
– Camera vibration – try mirror lockup
– Shaky mount – use weights
– Scope alignment and balancing
– “Ghost” images – remove UV filter from lens
• Taking memory card out before images have been saved
• DSLR batteries run out (keep a spare handy)
• Dew
Ghost Image
Where to publish
• Stargazers Lounge for feedback
• Flickr – many astrophotography groups
• Astronomy Now Facebook Group
• Sky and Telescope
• SpaceWeather.com
• Many other specialty websites
• Magazines:
– “The Astronomer”
– S&T, Astronomy Now, Sky at Night
– BAA Journal
Summary
• Astrophotography is accessible to most people -
even in a city!
• Entry level costs are a few hundred pounds
• Equipment is easily available
• Information readily available on the web
• Have fun!
Recommended Reading
• Astrophotography for the Amateur – Michael Covington
• Digital SLR Astrophotography – Covington
• Digital Astrophotography: A Guide to Capturing the Cosmos - Stefan Seip
• Search via Google
• http://stargazerslounge.com/
• http://heavens-above.com/
• http://www.calsky.org/
• http://www.skyandtelescope.com/