Getting started with Digital Astrophotography - Part I Rodger King - May 2016
Flame Nebula orsehead Nebula.
Question Astronomy Which type of Telescope is better - A Lens or Mirror? 500-900 More compact All the light is used No setup time Expensive per inch Heavier construction Smaller - less light Causes colour distortion APO Doublet/Triplet 300-400 Cheaper per inch Larger - more light Lighter per inch Second mirror blocks light Needs to cool down Needs to be setup Image distortion at edges Coma Corrector
Visual Astronomy Equipment Telescope Tripod Eyepiece
Question Visual Astronomy What is the exposure time of the human brain/eye? frames/sec Answer - it varies ~ 200/sec for very bright images, fast moving ~ 30-50/sec for normal images Slowest speed of few seconds per frame for very faint images
Digital Astrophotography No Limit To Exposure Time (KEY DIFFERENCE) ~11 times diameter ~120 more light collection What you can see = Hubble telescope = 2.3m My telescope = 0.2m Light Collection x Exposure Looking through the Hubble telescope is similar to a 300 second exposure using a camera on my telescope
Digital Astrophotography Extra Equipment Simple Camera (replaces your eye and brain) Phone Camera Compact Camera Lens-less Camera (replaces eyepiece, eye and brain) Webcam DSLR Camera
Digital Astrophotography Webcam Attached DSLR Attached
Digital Astrophotography Webcam - how much does it cost? ~ 15
Digital Astrophotography DSLR how much does it cost? ~ 115
Digital Astrophotography Got all our Equipment We are ready to go?
Digital Astrophotography Now the problems start
Astrophotography - Problems Most Astronomical objects are faint 1. Can t see anything in the picture 2. Can t get to or see into the viewfinder My setup shakes and spoils the picture 1. Touching it 2. Even walking passed it 3. Pressing the shutter Objects are moving 1. Moves ¼ deg in 1 minute
Astrophotography - Solutions Most Astronomical objects are faint Can t see anything in the picture 1. Manual setting ( M ) 2. High ISO - 800 or 1600 3. Long exposure 5, 10, 30 seconds or more (B setting). 800 B. 800.
Astrophotography - Solutions The stars are faint Can t get to or see into the viewfinder Use a right angled viewfinder
Exposure Times for Stellar Objects Moon? Saturn? Bright star cluster Faint stars Bright Nebula or Galaxy? Faint nebula or Galaxy? 150 th second 1/5 th second 1 100 seconds 1-300 seconds 1-300 seconds 1000 s seconds ONLY the B setting on DSLR cameras will allow you take pictures > 30 or 60 seconds
Exposure Time? 2 Million Seconds 23 Days
Astrophotography - Solution My setup shakes and spoils the picture When you press the shutter Buy one of these Remote Control
Astrophotography - Solution My setup shakes and spoils the picture When you touch it Even walking passed it ANSWER: New Tripod X
Astrophotography - Solution Objects are moving Moves ¼ deg in 1 min
Astrophotography - Solution Objects are moving Moves ¼ deg in 1 min How Quickly will stars trail? Small telescope? Medium Telescope? 1 second < ½ second
Exposure Times for Stellar Objects Moon? Saturn? Bright star cluster Faint stars Bright Nebula or Galaxy? Faint nebula or Galaxy? 150 th second 1/5 th second 1 100 seconds 1-300 seconds 1-300 seconds 1000 s seconds
Astrophotography - Solution Objects are moving Moves ¼ deg in 1 min Exposure < 1 second Buy one of these : ~ 500-1000+
Solving more problems Light Pollution Night sky is red not black Seeing the results Viewfinder small How do I tell if its a good picture? Wished I had taken 2 pictures Bumped the mount EasyJet plane passed through the picture
Astrophotography - Solutions Light Pollution Night sky is red not black ANSWER : Use a light pollution filter ~ 50 ~ 100
Astrophotography - Solutions Seeing the results Viewfinder small How do I tell if its a good picture? Use a wireless memory Card Transfer it instantly to a tablet or Computer ~ 50
Astrophotography - Solutions Wished I had taken 2 pictures Bumped the mount EasyJet plane passed through the picture take many shots ~ 60
Solving more problems Cannot focus accurately Stars are not points Is one telescope enough? Do I need more than one telescope? I cannot centre on the object Object too faint to see in viewfinder How do I know I have the object in the picture?
Astrophotography - Solutions Cannot focus accurately The stars are not points Use one of these : Its called a Bahtinov Mask ~ 10
Astrophotography - Solutions Stars are not points Its impossible to get an accurate focus
Is one telescope enough? DSLR use many different lenses Fixed Lenses Standard lens e.g. 50mm Wide-angle lens e.g. 18mm Telephoto Lens e.g. 300 mm Zoom lenses e.g. 50-250 mm Why? Astrophotography is no different Telescopes are Fixed Lenses of type telephoto
Is one telescope enough? Small Telescope 400, 500, 600 mm Medium Telescope 800, 1000, 1500 mm Large Telescope 1500+ mm Hubble Space Telescope? 57600 mm Zoom Capable 3000-57600
1000 mm 1500 mm 500 mm 1000 mm 1500 mm 1000 mm 57600 3000 mm 1500 mm
Solving more problems I cannot centre on the object Object too faint to see in viewfinder Use one of these Its a Go To system Often comes with a motorised tripod Has location of 1000 s of objects Needs to be aligned first!
Aligning a Go To system Every time you use the telescope Need to point tripod north accurately Need to have tripod level Next you align it Pick a bright star and press Enter It misses by a bit You use the handset and move until the star is back in the centre of the image Do again for at least 2 if not more stars Then it knows how to compensate for errors This can take up to 1 hour
Webcam using 8 Reflector
DSLR using 8 Reflector
DSLR using 3 Refractor
DSLR using 3 Refractor webcam
DSLR using 8 Reflector
DSLR using 8 Reflector
DSLR using 3 Refractor
Not able to take this yet We need Part II
of Part I http://www.rodgerking.co.uk mail@rodgerking.co.uk