Photographing the Night Sky DSLR Astrophotography Phil North FODCC 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 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 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 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 My Kit • Canon 5D MK 3 • Lens • 200mm F2.8 • 100mm 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 Camera Settings 26 October 2015 © Phil North FODC 7 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 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 9 500 Rule Gives the Maximum exposure time without noticeable star trailing. Divide 500 by the focal length. Focal Length Full Frame Max Exposure Crop sensor Max Exposure Sensor 1.6x 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 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 Full f Exposure ISO Crop f number Exposure ISO Length Frame number sensor Sensor 1.6x 24mm 24mm f2.8 20s 2400 38mm f4.48 13s 6400 26 October 2015 © Phil North FODC 11 Moonlit Landscapes 26 October 2015 © Phil North FODC 12 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 30 – 70 degrees, after astronomical twilight 26 October 2015 © Phil North FODC 13 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 400 - 1000 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 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 Moonlit Landscapes Canon 5Dmk3, Sigma 24mm f2.8 20sec ISO 1000 26 October 2015 © Phil North FODC 16 Moonlit Landscapes Canon 5Dmk3, EF17- 40mm f4.0 25sec ISO 2000 26 October 2015 © Phil North FODC 17 Night Sky Photography 26 October 2015 © Phil North FODC 18 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 Light Pollution 26 October 2015 © Phil North FODC 20 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 Histogram 26 October 2015 © Phil North FODC 22 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 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 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 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.