Basic Astrophotography - WordPress.com · 2016-01-05 · About me • Amateur Astronomer for over 40 years • Active observer as a student • Some astrophotography with 35mm film

Basic Astrophotography

Dr James West

Twitter: @ejwwest

Flickr: ejwwest

ejw_west@talk21.com

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/