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Imaging
with a DSLR camera
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| Torches:
Use a Red Light
Torch (preserves night vision): Cameras: DSLR Cameras normally record date/time of the image into the image, as well as other useful info like ISO/Aperture & Exposure The following are useful Features in a DSLR: o Back Panel with
Settings and Image Preview Get used to finding
& using your camera controls in the dark Batteries: Always charge after every use - don't wait until you need them to charge them. Carry Spares - Label each one so you know which have been used already o Single camera
battery lasts up to 2-2.5 Hours Lenses: Sharpness is very important - check online forums for user experiences with specific lenses Sharpness falls off the edge of lens - sharpest in centre Wide angle (10mm - 50mm) for whole constellations /Milky Way / Astro-Landscapes Medium Lens (50mm - 135mm) for parts of constellations / Large features like Nebulae Zoom Lens (160mm
upwards) for small objects like Can make a light
tube to avoid extraneous light in lens Filters: Can reduce local light pollution - need longer exposures Can image without them for Broad Spectrum targets like Galaxies / Clusters Most DSLR have built-in UV/IR Filter - removed for Astro-modified cameras. Removing IR filter can give better results for Hydrogen targets (Nebulae) but is not trivial to do. Still have good results with IR filter fitted. Moon Filter can reduce Moon Glare Never use anything
but Solar filter for imaging the Sun Focus: Infinity on dial not always correct Take image of stars then zoom in. Look for dots of light - discs of light are signs of poor focus. Focus cannot be fixed in later processing so get it right before starting a session. For Moon, focus either on stars first or on Moon terminator Can also use Bahtinov Mask for good focus on bright star When focus found,
can fix the lens focus position with tape Accessories: Memory Cards - Use Class 10 cards where possible Tripod - Sturdiest possible, Full Rotation, Use at lowest Height for stability Intervalometer - Reduces camera shake, allows Long Sequence Programs easily, Long Battery Life, Buy for Camera Model (connector type) Dew Heater - USB or 12V. Prevents dew forming on lens Red Dot Finder - For use with DSLR use Hot Shoe Adapter, Helps Locate Targets (some use laser pointers) Lens Hood - prevents stray light / Moon etc entering lens Spirit Level - level
the tripod before use. Very important when using Star Tracker or larger
mounts Exposures: Manual Mode &
either shutter speed to 2-30 seconds or ISO - Look online
for Optimum Setting for each camera If a f1.8 lens then
set to f2.8 or f4
Imaging Session: Choose Target: o Which Lenses you
have Install Stellarium on PC - see what is available that night & size etc - what to image and still avoid the moon Install Carte-du-Ciel (Skymap) on PC and print out target detail to Star-Hop to target when looking at stars Choose Weather: o Wind frequently
dies down after dusk but will cause vibrations in tripods if still present Frames/Subs: Take a minimum of
Light and Dark Frames for each Lights - images of the stars! As many as you can. Darks - same settings as Lights but cover lens with cap. Records - camera noise (take minimum of 10) Flats - Use Aperture
Priority setting (dependent on light for good exposure) and a uniform
light source across the frame (mobile phone with white screen or similar)
over the whole lens. Records blemishes in images - dust Start with setting
optimum ISO for your camera. Then go two up from minimum f stop (aperture).
Then set maximum exposure time you can for the focal length of your
lens. Try a test shot. Review the image and view the It's up to you whether you take the Darks / Flats at the end or beginning of the session If you can save
images to different folders on your memory card then save all images
for a target into one folder. You may want to use the 1st folder for
your rough images on all targets, then switch to a different folder
to Use hard ground if available. Stand away from the tripod - ground movement will likely show on the image. Avoid touching the camera - use a remote release or (better) an intervalometer. In that case set an initial delay of 10s to allow time to start the sequence and put the intervalometer down long before images start capturing If clouds appear then do the Darks/Flats Routine Have a routine for
setting up the same way every time. 1. Level Tripod * Only needed when
using star tracker or mount
Lucky Imaging For Lunar/Solar
then use the video function of the Capture 2,000 frames
per video. Use different processing software to extract the best images
(e.g. Autostakkert and PiPP ) Stacking: Software to add images together to Increase Detail and Contrast / Remove noise. Lunar/Solar is Lucky Imaging Free - To Stack
Stars - Paid - To Stack
Stars - Free - For Lunar/Solar Most offer 30-60
day free trials Processing: Software to bring
out the stacked Image Data into usable Free Paid Most offer 30-60 day free trials
Useful Links: Club Site: A PDF version of these notes is available HERE Compiled by Damian Ohara (Swindon Stargazers) v0.02 |
