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9 th January 2008Terry Evans, Bridgwater Astronomical Society First Steps In Astrophotography.

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Presentation on theme: "9 th January 2008Terry Evans, Bridgwater Astronomical Society First Steps In Astrophotography."— Presentation transcript:

1 9 th January 2008Terry Evans, Bridgwater Astronomical Society First Steps In Astrophotography

2 9 th January 2008Terry Evans, Bridgwater Astronomical Society First Steps In Astrophotography Cameras and what they can do Short exposure imaging Long exposure imaging Processing Some tricks

3 9 th January 2008Terry Evans, Bridgwater Astronomical Society Cameras (and what they can do) Camera types Strengths and limitations of camera types Best subjects for camera types

4 9 th January 2008Terry Evans, Bridgwater Astronomical Society Camera Types Digital or Film Simple “point & shoot” More complex Point & shoot Single Lens Reflex cameras Webcams CCD Cameras

5 9 th January 2008Terry Evans, Bridgwater Astronomical Society An (Important!) Aside! Start with what you’ve got Get a camera which isn’t just for astronomy Get a tripod

6 9 th January 2008Terry Evans, Bridgwater Astronomical Society Digital or Film Film – bit old hat but still good for some subjects Digital – rapidly improving format with lots of variations

7 9 th January 2008Terry Evans, Bridgwater Astronomical Society Film Good cameras are very cheap on e-bay Film processing takes time High “Dynamic Range” (about bits) Large “sensor” (35mm) 35mm film is equivalent to about 20 M Pixels Further processing requires scanning

8 9 th January 2008Terry Evans, Bridgwater Astronomical Society Digital Prices for “high end” cameras reducing quickly.Cheap cameras aren’t really coming down in price (just increasing pixel count) “Instant” results Limited dynamic range (8 to 14 bits) Small sensors (typically 10mm across) Easy digital enhancement and stacking

9 9 th January 2008Terry Evans, Bridgwater Astronomical Society Simple Point & Shoot

10 9 th January 2008Terry Evans, Bridgwater Astronomical Society Simple Point & Shoot  Auto Exposure only  Auto Focus only  Small Sensor and dynamic range Nearly always have a “live view” on LCD screen (WYSIWYG) Light and cheap (£50 up) Probably have one already!

11 9 th January 2008Terry Evans, Bridgwater Astronomical Society More complex Point & Shoot

12 9 th January 2008Terry Evans, Bridgwater Astronomical Society More complex Point & Shoot Exposure Control  Probably no focus control Up to APS (26mm) sized sensor  Limited Dynamic Range (8 bit jpg files) Live View  Fixed Lens Has a Filter Ring  Becoming bulky and more expensive. £150

13 9 th January 2008Terry Evans, Bridgwater Astronomical Society Digital SLR

14 9 th January 2008Terry Evans, Bridgwater Astronomical Society Digital SLR  Pricey – Typically £400 with lens but good 2 nd hand market Full exposure and focus control APS or 35mm sensor 12 or 14 bit dynamic range (Raw file)  No Live view except on most recent models Removable lens so can attach to telescope

15 9 th January 2008Terry Evans, Bridgwater Astronomical Society Webcams

16 9 th January 2008Terry Evans, Bridgwater Astronomical Society Webcams  Take a video stream that can be stacked into a single image Dead cheap (£30 - £60)  Very small sensor  Limited to bright subjects  CCD Type best (ToUcam, SPC 900NC) Cheap adaptor connects to telescope

17 9 th January 2008Terry Evans, Bridgwater Astronomical Society CCD Camera

18 9 th January 2008Terry Evans, Bridgwater Astronomical Society CCD Camera  £400 up (and up..) Good 2 nd hand deals Cheap T Adaptor to connect to scope  Needs capture software (maybe bundled) Low noise High sensitivity and dynamic range  Specialised astro gear

19 9 th January 2008Terry Evans, Bridgwater Astronomical Society What can they do? Daytime pictures (Sunrise/set, halos, sundogs, etc) Constellation and wide field Moon Planets Long exposure telescope imaging

20 9 th January 2008Terry Evans, Bridgwater Astronomical Society Daytime Pictures Auto Exposure Point & Shoot Good. Convenient to carry for the unexpected Manual Exposure Point & Shoot Very Good. Allows “bracketing” of exposure Digital SLRVery Good WebcamNo CCD CameraNo

21 9 th January 2008Terry Evans, Bridgwater Astronomical Society Moon Auto Exposure Point & Shoot Good Using Afocal method Manual Exposure Point & Shoot Potentially Very Good if coupled using filter ring Digital SLRVery Good if using telephoto lens or scope WebcamExcellent through scope Small field of view CCD CameraOK but usually too sensitive

22 9 th January 2008Terry Evans, Bridgwater Astronomical Society Planets Auto Exposure Point & Shoot Planet too small for reliable results Manual Exposure Point & Shoot Planet too small for reliable results Digital SLRPossible using eyepiece projection but not good WebcamExcellent through scope Can get very good detail CCD CameraToo sensitive and planet too small

23 9 th January 2008Terry Evans, Bridgwater Astronomical Society Constellation & Wide Field Auto Exposure Point & Shoot Poor. Usually limited to short exposures Manual Exposure Point & Shoot OK if 10 to 30 second exposure allowed Digital SLRGood if undriven, very good if driven WebcamNo CCD CameraVery Good if matched with “T” SLR lens

24 9 th January 2008Terry Evans, Bridgwater Astronomical Society Long Exposure Telescope Imaging Auto Exposure Point & Shoot No Manual Exposure Point & Shoot No Digital SLRVery Good WebcamNo CCD CameraExcellent

25 9 th January 2008Terry Evans, Bridgwater Astronomical Society Daytime exposures (with “normal” lens) Views and phenomena Sunrises & Sunsets Moon Eclipses Tripod a good idea Bracket exposures

26 9 th January 2008Terry Evans, Bridgwater Astronomical Society Moon and Venus 2008/01/05 07:30 Canon 300D 55mm 1/10s F/ ISO Tripod

27 9 th January 2008Terry Evans, Bridgwater Astronomical Society Partial Lunar Eclipse 2006/09/08 21:00 BST Canon 300D 400mm 1/160s F/ ISO Tripod

28 9 th January 2008Terry Evans, Bridgwater Astronomical Society Noctilucent Clouds 2006/07/14 22:44 BST Canon 300D 27mm 2.5s f/8 800ISO Tripod

29 9 th January 2008Terry Evans, Bridgwater Astronomical Society Moon 22° Halo 2007/01/05 22:07 Canon 300D 22mm 10s f/ ISO Tripod

30 9 th January 2008Terry Evans, Bridgwater Astronomical Society Moon and Venus 2004/01/24 17:44 Minolta Dimage-X 17mm Auto-exposure f/ ISO Wedged

31 9 th January 2008Terry Evans, Bridgwater Astronomical Society Short Exposure Imaging with a Telescope Moon and Planets Sun with solar filter Need to provide high magnification for planets and crater detail Use eyepiece projection and “afocal” imaging

32 9 th January 2008Terry Evans, Bridgwater Astronomical Society Afocal Imaging Point camera with lens through telescope eyepiece!

33 9 th January 2008Terry Evans, Bridgwater Astronomical Society Lots of vignetting and need to be careful with focus. Starts like this

34 9 th January 2008Terry Evans, Bridgwater Astronomical Society But careful composition and focus gets you this with an afocal DSLR

35 9 th January 2008Terry Evans, Bridgwater Astronomical Society Or this with a simple point & shoot camera

36 9 th January 2008Terry Evans, Bridgwater Astronomical Society Or this with a camera phone (not mine)

37 9 th January 2008Terry Evans, Bridgwater Astronomical Society Improving Afocal images PVC tube over the eyepiece Camera attachment

38 9 th January 2008Terry Evans, Bridgwater Astronomical Society Improving Afocal images PVC tube over the eyepiece Camera attachment Filter ring attachment

39 9 th January 2008Terry Evans, Bridgwater Astronomical Society Webcam Imaging Best way for planets Attach to scope with 1¼ inch adaptor Essential to replace IR filter

40 9 th January 2008Terry Evans, Bridgwater Astronomical Society Webcam Imaging Need a computer! Use Webcam software to record about 10s AVI Use Registax to stack the AVI Fiddle with Wavelets to bring out detail Registax Demo

41 9 th January 2008Terry Evans, Bridgwater Astronomical Society

42 9 th January 2008Terry Evans, Bridgwater Astronomical Society Constellation and Wide Field Need a camera which allows 10 to 30s exposures Need a tripod Lens of about 50mm (35mm equivalent) Stacking software (DeepSky Stacker)

43 9 th January 2008Terry Evans, Bridgwater Astronomical Society

44 9 th January 2008Terry Evans, Bridgwater Astronomical Society

45 9 th January 2008Terry Evans, Bridgwater Astronomical Society Trailing The Earth rotates about its axis every 24 hours The stars appear to rise in the East and set in the West The amount of motion detected on the sensor is proportional to the magnification and the duration of the exposure

46 9 th January 2008Terry Evans, Bridgwater Astronomical Society Trailing Formula Trail Length = F*E*T*cos(D)/ Pixel size where: F = Focal length of lens/scope (mm) E = Exposure length (Sec) T = 2*  /86400 D = Declination of the star

47 9 th January 2008Terry Evans, Bridgwater Astronomical Society Star Trail Lengths on Canon 300D Pixel size 7.1 microns Focal LengthExposureDeclinationTrail Length 55mm30s017 pixels 24mm30s07 pixels 55mm10s05 pixels 55mm30s608 pixels 24mm10s601.2pixels 400mm10s0123 pixels

48 9 th January 2008Terry Evans, Bridgwater Astronomical Society Orion 35mm fl

49 9 th January 2008Terry Evans, Bridgwater Astronomical Society Closeup of the Belt Stars

50 9 th January 2008Terry Evans, Bridgwater Astronomical Society Tracking the Stars Piggy-back on a telescope

51 9 th January 2008Terry Evans, Bridgwater Astronomical Society Tracking the Stars Piggy-back on a telescope Dedicated Camera tracker

52 9 th January 2008Terry Evans, Bridgwater Astronomical Society Tracking the Stars Piggy-back on a telescope Dedicated Camera tracker Barn Door Mount

53 9 th January 2008Terry Evans, Bridgwater Astronomical Society Long Exposures with a Telescope Need: SLR or CCD camera (prime focus) Coupling between camera and telescope A way to take pictures Good solid driven mount Way to focus accurately

54 9 th January 2008Terry Evans, Bridgwater Astronomical Society Coupling to Telescope Coupling via T mount and T-eyepiece adaptor “Nosepiece” Fully Screw-in system more robust but less flexible (e.g. SCT coupling) Focal Reducer can be used to widen field of view

55 9 th January 2008Terry Evans, Bridgwater Astronomical Society Taking Pictures with Digital SLR Stand AloneComputer Control You control the exposures directly Set up a sequence and let the computer do the exposures Feedback is through the LCD screen Can display first exposures to make sure they’re right Images stored in the camera memory card Can save in the camera or download to computer Needs lots of batteries but can be done anywhere Need power supply for the computer

56 9 th January 2008Terry Evans, Bridgwater Astronomical Society Stand-Alone DSLR shooting Need remote shutter release (can be wireless!) to avoid shake (£15) Set shutter speed to longest available if no “bulb” Set Mirror lockup if available Set resolution to “RAW” or best available Need lots of room on the memory card

57 9 th January 2008Terry Evans, Bridgwater Astronomical Society DSLR Remote Control H/W USB cable for control and download Probably need separate cable for “bulb”, about £15 for a serial cable

58 9 th January 2008Terry Evans, Bridgwater Astronomical Society DSLR Remote Control S/W Remote control using camera software or dedicated astro-sw, e.g. DSLR Focus (£25) DSLR Shutter (Free)

59 9 th January 2008Terry Evans, Bridgwater Astronomical Society Good Solid Driven Mount Needs to be solid enough for the telescope plus the camera Need to get the balance right and may need more counterweight Longest exposure dependent on polar alignment (Field Rotation) Alt-Az OK for short exposures. Automated stacking takes care of field rotation

60 9 th January 2008Terry Evans, Bridgwater Astronomical Society Accurate Focus Remote control software has focus mode Use bright star for focussing Live View cameras make this easy (zoom) Hartmann Mask / Diffraction Spikes

61 9 th January 2008Terry Evans, Bridgwater Astronomical Society

62 9 th January 2008Terry Evans, Bridgwater Astronomical Society

63 9 th January 2008Terry Evans, Bridgwater Astronomical Society Processing Can’t put back what wasn’t there! Stacking to increase Signal to Noise Ratio Aligning to minimise tracking and field rotation issues Post-processing to enhance the signal

64 9 th January 2008Terry Evans, Bridgwater Astronomical Society Stacking Adds (or averages) a number of images Produces in increase in S/N ratio Makes the image smoother Mimics the effect of a longer exposure Exposure Effective =  Num exposures*Exposure Short exposures reduce: –Tracking errors –Lost Exposures because of cloud or satellites

65 9 th January 2008Terry Evans, Bridgwater Astronomical Society Aligning Makes sure each image aligns with the others for stacking Manual 1 star alignment for tracking 2 star alignment for tracking and rotation Automatic star matching Correlation (Registax)

66 9 th January 2008Terry Evans, Bridgwater Astronomical Society Aligning & Stacking Software Registax (Free) DeepSky Stacker (Free) IRIS (Free but very complex to use) Images Plus ($200) Astroart (£120) MaximDL (expensive but best $459)

67 9 th January 2008Terry Evans, Bridgwater Astronomical Society Post-Processing Photoshop (in its various guises) Paintshop-Pro Images Plus, Maxim & Astroart have some nice features (DDP & FFT filters)

68 9 th January 2008Terry Evans, Bridgwater Astronomical Society Photoshop Various versions CS3 (hugely expensive, student version) Elements (£60) but sometimes free with equipment Various older versions (typically 8 bit)

69 9 th January 2008Terry Evans, Bridgwater Astronomical Society Photoshop Manipulation Levels Curves Sharpening filters Noise / blur filters Layers and masks

70 9 th January 2008Terry Evans, Bridgwater Astronomical Society Blurred layer to remove gradients Duplicate as new layer Use “Dust&Scratches” to remove stars Change mode to Difference

71 9 th January 2008Terry Evans, Bridgwater Astronomical Society

72 9 th January 2008Terry Evans, Bridgwater Astronomical Society Wash Layer to Increase Colour Duplicate image as a layer.Select layer Filter Median and Gaussian Blur Increase Saturation Change mode to Color (sic)

73 9 th January 2008Terry Evans, Bridgwater Astronomical Society

74 9 th January 2008Terry Evans, Bridgwater Astronomical Society Layer Masks to Increase Range Duplicate image Manipulate with curves, etc Layer on original (ctrl-A,ctrl-C and ctrl-V) Create a mask, select (alt click) and ctrl-V Gaussian blur the mask (~10 pixels) Select the layer 1 image Merge down when happy

75 9 th January 2008Terry Evans, Bridgwater Astronomical Society

76 9 th January 2008Terry Evans, Bridgwater Astronomical Society Buying Second Hand Active upgrading so not just throwaways Very active site (15 listings per day) Less busy but all good stuff E-bay Some gems but 99% tat American sites for the adventurous

77 9 th January 2008Terry Evans, Bridgwater Astronomical Society Things I’ve Left Out!! DSLR H-Alpha response and modification Bias, Darks & Flats Polar Alignment Guiding Motorised focussing CCD imaging And lots more…


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