photo:ast_photodigital1
astrophotography with digital cameras
Choosing a dSLR for deep sky astrophotography:
see also:
in the days of film, the legendary
Olympus OM-1n was king of astrophotography as it was light, had mirror lockup, bulb time exposure with cable release, worked without batteries and you could buy focussing screens that enabled easier focus when used on long focal length lenses. But today digital is king, although battery life can be an issue, particularly if you want to do those star trails over several hours!
most beginners should aim to take multiple 60sec sub-exposures at ISO 800-1600 and at f/2.8 in dark skies with focal lengths no longer than 300mm in 35mm terms using a tracking mount (unless you have a really good mount +/- autoguiding gear).
you can use longer focal lengths (eg.
prime focus with camera attached through a telescope) for bright subjects such as the
moon and Jupiter, but for other subjects you will need a VERY GOOD mount probably with auto-guiding system to get good results.
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ideally the camera should have:
low noise at high ISO (most currently use ISO 800-1600)
full frame mirrorless is probably the best way to go
in light polluted sites, sub-exposures are limited by the light pollution anyway so lower ISO's are better (eg. 400-800).
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see
Roger Clark's many articles on sensor performance in low light situations
true RAW mode that doesn't obliterate faint stars
its IR filter replaced with UV/IR Ha-enhanced filter to give good nebula images via improved Ha infrared response
modern dSLRs block the H-alpha region allowing only ~27% transmission, removing the IR blocking filter increases transmission to nearly 98%, thereby giving 4x more sensitivity or 2EV for H-alpha nebulae.
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Live Preview to accurately manual focus or many modern mirrorless cameras have star light AF mode
preferably an articulating LCD so you don't get a sore back
high quality prime lens (not a zoom lens) with good performance at aperture f/2.0-f.2.8 at 35mm effective focal length 200-300mm, preferably without optical IS which degrades star images.
lenses wider than 100mm in 35mm terms have limited utility as light pollution gradients are problematic and the lens preclude the use of interference type filters such as most narrow band light pollution filters, while the only objects for a wide angle are the Milky Way, aurorae and perhaps meteor showers, but if you do wish to try them out, be aware that you will need to stop them down for good star images: eg: 50mm lens at f/2.8-4, 28mm lens at f/5.6.
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for Canon dSLRs:
most get the Canon EF 200mm f/2.8 L non-IS lens with the tripod mount ring (buy separately as not supplied), better star shapes at f/3.2
Canon 100mm f/2.8 USM macro gives excellent results at f/2.8 (don't use the older non-USM one) as does the 100mm f/2.0 when used at f/2.5.
one might also consider the Canon 135mm f/2.0L although there seems to be little experience on the web forums.
for full frame or APS-C:
be light, compact with good battery for cool conditions
mirror lockup, or better still use a mirrorless camera:
timed 60sec exposures as this is the most commonly used sub-exposure duration
Olympus has this but you need a TC-80N3 Timer Remote Controller for Canon dSLRs (but not available on the Rebel dSLRs)
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You can't remote release many Nikon dSLRs (eg. D40) using Camera Control Pro when the camera is in Bulb mode, you need to buy 3rd party tools like Shoestring Astronomy's DSUSB-IR and download DSLR Shutter from Stark Labs.
time lapse facility so you can do 20-100 sub-exposures easily
for Canon dSLRs, use the TC-80N3 Timer Remote Controller (with N3-capable dSLRs)
Nikon D300 has a built-in intervalometer
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other accessories to consider:
Hutech front filter LPS-V3, $US299
a good quality portable tracking mount:
TC-80N3 timer for Canon 1D, or modified for the 450D
Using a digital camera at higher magnifications:
photo/ast_photodigital1.txt · Last modified: 2021/12/05 00:35 by gary1