Photographing the Night Sky DSLR Astrophotography. Phil North FODCC

Transcription

1 Photographing the Night Sky DSLR Astrophotography Phil North FODCC

2 Agenda Introduction Moonlit Landscapes Night Sky Photography Milky Way Star Trails Time Lapse Some Examples Coffee Break Photoshop Techniques 26 October 2015 Phil North FODC 2

3 What is Astrophotography Astrophotography is a large sub-discipline in amateur astronomy and is the process of producing photographs of objects in the universe and large areas of the sky. It can be done with standard photography equipment to specialised equipment requiring significant financial investment. Astrophotography is relatively easy in the beginning stages but becomes difficult at advanced levels. Advance level requires use of telescopes, tracking mounts and specialised CCD cameras 26 October 2015 Phil North FODC 3

4 Types of Astrophotography Deep space images which are taken with use of a telescope of objects beyond our own solar system. These are those stunning images you see of distant galaxies and nebulae, and this is the most technical and hardest form of astrophotography. Wide Field this is astrophotography that is taken with a DSLR camera and wide angled lens. These are the images you see that include a starry sky or star trails above a landscape. This is the most accessible form of astrophotography, and are the kind I practice and will be talking about. Time-lapse Astrophotography is just an extension on Wide Field Astrophotography. The only difference is you take lots of exposures over time and then combine the frames to make a time-lapse video. The same technique can be used to make a star trail image. 26 October 2015 Phil North FODC 4

5 What You Need A camera that has manual exposure mode A bulb setting for exposures longer than 30s A remote control or a shutter release cable in order to minimise shaking the camera when taking the pictures. A wide angle lens with a fast aperture F1.4 to F2.8 is ideal Most Importantly a sturdy tripod 26 October 2015 Phil North FODC 5

6 My Kit Canon 5D MK 3 Lens 200mm F mm F2.8 50mm F1.4 24mm Wide Angle F1.8 15mm Fish Eye F2.8 Remote Shutter Release (hahnel Giga T Pro) Manfrotto tripod with ball head ioptron SkyTracker Used for photographing deep sky objects 26 October 2015 Phil North FODC 6

7 Camera Settings 26 October 2015 Phil North FODC 7

8 Lens Aperture Use a lens that is at least f/2.8 for fixed tripod shots so you can use relatively short exposures. This will lessen the amount of star trailing when shooting on a fixed tripod for pin point stars. If shooting on a polar-aligned equatorial tracking mount, the f/stop of the lens is not as critical because you can always shoot longer exposures without trailing. In most cases the lens must be stopped down a stop or two from wide open to improve coma, astigmatism and chromatic aberrations enough to produce usable stars. Use without a UV filter filters reduce the amount of light falling on the sensor. 26 October 2015 Phil North FODC 8

9 Aperture and Shutter Speed APERTURE VS. ISO f/1.4 f/2.0 f/2.8 f/4.0 ISO1600 ISO3200 ISO6400 ISO12800 Less Noise More Noise FOCAL LENGTH VS. SHUTTER SPEED APS-C: 10mm 12mm 16mm 24mm Full Frame: 14mm 20mm 24mm 35mm Shutter: 30s 25s 20s 15s 26 October 2015 Phil North FODC 9

10 500 Rule Gives the Maximum exposure time without noticeable star trailin Divide 500 by the focal length. Focal Length Full Frame Sensor Max Exposure Crop sensor 1.6x Max Exposure 15mm 15mm 33s 24mm 21s 24mm 24mm 21s 38mm 13s 50mm 50mm 10s 80mm 6s 100mm 100mm 5s 160mm 3s 200mm 200mm 2.5s 320mm 1.5s 26 October 2015 Phil North FODC 10

11 Aperture,Exposure and Focal Length The f number of a lens is the focal length divided by maximum aperture so for a crop sensor the equivalent f number is larger. 100mm focal length f4 lens gives an aperture of 25mm On crop sensor (Canon) 160mm/25mm = f6.4 Therefore to get an equivalent exposure on a crop sensor the ISO must be increased. ISO is multiplied by square of the crop factor Focal Length Full Frame Sensor f number Exposure ISO Crop sensor 1.6x f number Exposure 24mm 24mm f2.8 20s mm f s October 2015 Phil North FODC 11 ISO

12 Moonlit Landscapes 26 October 2015 Phil North FODC 12

13 Moonlit Landscapes Photographing under the light of the moon can create dramatic, surreal landscape images. The full Moon s surface reflects an average of 12 percent of the sunlight that hits it. The soft moonlight is unlike the harsh daylight and interacts with the landscape in a different way. The lower the altitude of the moon the more dramatic are the shadows on the landscape. The most dramatic moonlit landscape photos come between degrees, after astronomical twilight 26 October 2015 Phil North FODC 13

14 Moonlit Landscapes For the best results, find a dark location away from the light pollution of major cities and towns. Shoot in RAW, Set White balance to 4000 K I ve found ISO and an aperture of f/4 provides me the best long exposure time/noise ratio under a full Moon. Plan your photo shoot 26 October 2015 Phil North FODC 14

15 Moonlit Landscapes Moon Phases chart from stardate.org I use the Photographers Ephemeris predict where the moon rise will be. I also use Google Earth to scout out an area that I m unfamiliar with. 26 October 2015 Phil North FODC 15

16 Moonlit Landscapes Canon 5Dmk3, Sigma 24mm f2.8 20sec ISO October 2015 Phil North FODC 16

17 Moonlit Landscapes Canon 5Dmk3, EF17-40mm f4.0 25sec ISO October 2015 Phil North FODC 17

18 Night Sky Photography 26 October 2015 Phil North FODC 18

19 Tips for Night Sky Photography Look for cool clear moonless nights for the maximum number of stars and the milky way The moon can be used to illuminate the landscape but will reduce the amount of stars that can be captured. Avoid light polluted areas (big cities or towns). Start with fresh, fully charged batteries Star trails will take several hours of exposure. Shoot RAW so you can more easily make adjustments in post-production 26 October 2015 Phil North FODC 19

20 Light Pollution 26 October 2015 Phil North FODC 20

21 Tips for Night Sky Photography Set Camera to Manual Mode. A good starting exposure for most star shots is to use the widest aperture on your lens, expose for 20 seconds (24mm full frame sensor), increasing the ISO as needed for a good exposure. Stars move at about 2.5 degrees every 10 minutes around the celestial pole. Use the 500 Rule to determine the maximum exposure time to avoid star trailing with the focal length lens you are using. Set the white balance between 3000 K-4000ºK. 4000ºK works well for moonlight, I use 3800ºK for moonless nights. Check the histogram after you take the picture to make sure the image is being properly exposed. It s easy to underexpose the stars or overexpose a foreground. 26 October 2015 Phil North FODC 21

22 Histogram 26 October 2015 Phil North FODC 22

23 Tips for Night Sky Photography Turn ON the camera s Long Exposure Noise Reduction feature. Except if stacking images and using dark frame reduction for star trails. On camera noise reduction records a dark frame and subtracts from the image. On camera noise reduction doubles the time between each exposure. Manual Focus at infinity as a starting point. Auto focus will not work Use live View and zoom in to a bright star to adjust Focus. Keep checking the front of the lens for condensation. Use red torch light when adjusting camera settings to preserve night vision 26 October 2015 Phil North FODC 23

24 Tips for Night Sky Photography If you can t see the Milky Way with your naked eye, it will be very hard to capture it any better on camera. If you are in a dark enough location the milky way should be visible to the naked eye. There are several major constellations along the Milky Way galactic plane: Scorpio, Sagittarius, the Summer Triangle, Cassiopeia, the Southern Cross and Orion. There are several apps to help in finding the milky, I use Stellarium it is available for Android and IOS but I use the free version available for Mac, Linux and Windows (stellarium.org) 26 October 2015 Phil North FODC 24

25 Tips for Photographing the Milky Way and Stars If the moon is out you are not going to capture the Milky Way very well or that many stars. On the moonless nights, the sky is darker and the Milky Way looks better with more depth and contrast. However if there is a crescent Moon low at the horizon, it may be effective in illuminating the landscape without affecting the sky much. It is always a good idea to include some foreground interest to accompany the Milky Way and stars in your photo Its worth also taking a photo before its dark and then merging the two together in Photoshop 26 October 2015 Phil North FODC 25

26 Tips for Photographing the Milky Way and Stars Almost any time of the year, better from September to end of November at clear cloudless nights. Summer months (end July to end August) are good if you don t mind being out all night as the Milky way is at its brightest. Use the 500 Rule for photographing the Milky Way Take the number 500 and divide it by the focal length you will be shooting at. For those that are not shooting with full frame cameras make sure to take this into account. 26 October 2015 Phil North FODC 26

27 Tips for Photographing the Milky Way and Stars Experiment with the settings, aperture, exposure and ISO until you are getting the shots you like. Each of them directly reflect on each other and the amount of light that hits your sensor. So a slight change could make all the difference in the stars you can see. ISO anywhere from Play around and see what you get, starting at ISO1600 and working your way up. I normally use ISO 3200 or 6400 for a 20sec exposure Only compensate with ISO after your exposure is at it's 500 Rule maximum 26 October 2015 Phil North FODC 27

28 Photographing the Milky Way and Stars Light pollution can clearly be seen reflected of the clouds. Canon 5Dmk3 Sigma 24mm f2.0 20sec ISO October 2015 Phil North FODC 28

29 Photographing the Milky Way and Stars It is still possible to capture the Milky Way in the Forest. Light pollution can clearly be seen reflected on the clouds. Canon 5Dmk3, Sigma 15mm fish eye, f2.8 at 25 sec ISO October 2015 Phil North FODC 29

30 Star Trails The techniques in the field are relatively simple and easy. The trick to making compelling images comes at the computer in stacking dozens or hundreds of images into one composite. For shooting star trails you have two philosophies each with advantages and drawbacks. Shoot long exposure, low ISO and few images Lower noise but aircraft lights will require editing out, car headlight may make the image unusable. Shoot short exposure, high ISO and many images 200 or more images required but the same set of images can be turned into a time lapse movie. 26 October 2015 Phil North FODC 30

31 Star Trails For long exposures its essential to avoid overexposure. First take a test shot at a high ISO to get a well exposed image. e.g. if 30s at ISO 3200 looks good what would it be at ISO 100 to get from ISO 100 requires five doublings of ISO so the shutter speed requires 5 doublings from 30s i.e. 60>120>240>480>960s = 16min 26 October 2015 Phil North FODC 31

32 Tips for Star Trails When taking star trail pictures its not necessary to have the near "perfect" conditions that are required for Milky Way shots. Any night with a clear sky will work. On nights when the moon is out for star trails you can capture bright stars without increasing your ISO above 1000, thus reducing noise. At or close to a full moon ISO 400 is sufficient but it will not be possible to capture that many stars. Use a remote, timer/intervalometer with the camera set to bulb mode. This is key for taking exposures longer than 30 seconds or multiple shots over an extended period of time. 26 October 2015 Phil North FODC 32

33 Tips for Star Trails Locate the pole star the stars will rotate around this. 26 October 2015 Phil North FODC 33

34 Tips for Star Trails My preferred method for capturing star trail photos involves using multiple exposures each capturing a small star trail over an elapsed period of time (60s). The multiple images are then Stacked. Can be done in Photoshop but I use a free program called Startrails I also take 5 images with the lens cap on keeping the camera settings the same (known as a dark frame). I normally use a 50mm or 24mm lens for star trails 50mm 30minutes minimum, 24mm 60minutes minimum 26 October 2015 Phil North FODC 34

35 Tips for Star Trails The camera settings for each of these exposures is exactly the same. The only thing that changes is the position of the stars relative to the earth. The best part about this method is you can keep your exposure time low, between 30 and 60 seconds, while keeping your ISO fairly low thus reducing the overall high ISO and long exposure noise in your photos. Include a foreground subject that the stars can rotate around 26 October 2015 Phil North FODC 35

36 Tips for Star Trails Focal Length: For star trails any focal length will work. Keep in mind the further zoomed in you are the longer your star trails will appear over a shorter amount of time ( Ref: 500 Rule). If you don't want to wait around all night to capture a star trail scene a telephoto lens may be your best choice. If you're interested in capturing a full wide angle star trail scene showing a long star trail transition across the sky this may require a few hours (3-4) for the stars to exhibit trails through the full range view for your wide angle lens. 26 October 2015 Phil North FODC 36

37 Tips for Star Trails The best way to see this in physical form is to go out and try some test shots in the field with whatever lenses you have. See how different lenses or focal lengths exhibit different trial lengths over a given period of time. Another good reference is the 500 Rule chart, this will show the direct correlation between star trails and focal length in a mathematical manner. 26 October 2015 Phil North FODC 37

38 Post Processing For Star Trails Load all your images into a RAW photo processor of your choice such as Adobe Camera RAW or Lightroom. Adjust a single exposure out of the series to get the white balance, dark s, whites and all of the other settings to mimic what you would like to see in your final image. Now sync all of your other images from the shoot to exactly match this image. This is very easy using the "Sync" option in Camera Raw or Lightroom. 26 October 2015 Phil North FODC 38

39 Post Processing For Star Trails Remove unwanted lights (aircraft, cars, etc) from your images. Export all of your files to JPEG. Stack images using StarTrails.exe Images can be stacked in Photoshop but gaps will be left 26 October 2015 Phil North FODC 39

40 Star Trails Canon 5Dmk3, Sigma 24mm F5.6 60sec ISO 2000 Stack of 67 images + 3 Dark Frames 26 October 2015 Phil North FODC 40

41 Night Sky Time Lapse To generate a time lapse sequence the process is very similar to capturing star trails. Remember to use the 500 rule to avoid star trailing. One should bear in mind that a frame rate of 15 to 25 fps is needed for a smooth image sequence images to give approximately 1 minute of movie file At 20 sec per image (24mm full frame) is approximately 6 hours An avi file can be generated using the startrails program. Audio can be added using Windows Movie Maker. 26 October 2015 Phil North FODC 41

42 Night Sky Time Lapse Canon 5Dmk2, EF 16-35mm 16mm F2.8 10sec ISO 3200 Stack of 608 images 26 October 2015 Phil North FODC 42

43 Using Zoom Lens This is what can happen when pointing a zoom lens upwards 26 October 2015 Phil North FODC 43

44 Light Pollution Light pollution from man made lighting produces a colour cast and reduces the contrast and detail of the sky. Broadband light-pollution filters are available that can significantly improve deep-sky images by filtering out undesirable wavelengths dominated by light pollution. The image below left was taken without a filter and the one right was with a filter. The didymium glass filter used was a Marumi Redhancer. When using a filter the exposure has to be increased. 26 October 2015 Phil North FODC 44

45 Light Pollution 26 October 2015 Phil North FODC 45

46 Sample Images 26 October 2015 Phil North FODC 46

47 Star capture under a Full Moon 15mm Fish Eye F3.5 20sec ISO400 Colour Temp 4000K Adjusted for contrast and colour in Photoshop 26 October 2015 Phil North FODC 47

48 Star capture under a Full Moon 15mm Fish Eye F4.0 30sec ISO400 Colour Temp 4800K Adjusted for contrast and colour in Photoshop 26 October 2015 Phil North FODC 48

49 Star capture under a Full Moon 24mm F3.2 20sec ISO400 Colour Temp 4000K Adjusted for contrast and colour in Photoshop 26 October 2015 Phil North FODC 49

50 Star capture under Moonlight 24mm F2.8 20sec ISO6400 Colour Temp 3200K Adjusted for contrast and colour in Photoshop 26 October 2015 Phil North FODC 50

51 Star capture without Moonlight 24mm F2.8 20sec ISO6400 Colour Temp 3800K Adjusted for contrast and colour in Photoshop 26 October 2015 Phil North FODC 51

52 Free Resources Stellarium Provides a map of the stars from a location that can be defined ( StarTrails.exe A stacking program used to create star trails ( StarStaX - A stacking program used to create star trails ( The Photographers Ephemeris- Provides sun and moon rising and setting details Blue Marble Map showing areas of light polution (htp:// 26 October 2015 Phil North FODC 52

53 Youtube Videos Beginner DSLR Night Sky Astrophotography How to Edit the Milky Way in Photoshop How to edit the Milky Way - Photoshop Tutorial How to process a Milky Way image in Lightroom 26 October 2015 Phil North FODC 53