Astrophotography 20mm f/1.8 vs 14-30mm f/2.8
Apr 2, 2021 23:06:32 #
larryepage
Loc: North Texas area
baron_silverton wrote:
If you are using it for astrophotography it is a no-brainer - the 20mm 1.8 smokes the 14-30 f/4.
If it was just for landscape then I'd say 14-30 as you will be mostly shooting at around F/8-16 anyway. Once you add astro to the mix there is no question - 20mm 1.8 is the right lens of the two. It is 2.34 stops faster - this means much lower ISO and faster shutter speeds - both necessary to excellent astro photography.
Hope this helps.
-B
If it was just for landscape then I'd say 14-30 as you will be mostly shooting at around F/8-16 anyway. Once you add astro to the mix there is no question - 20mm 1.8 is the right lens of the two. It is 2.34 stops faster - this means much lower ISO and faster shutter speeds - both necessary to excellent astro photography.
Hope this helps.
-B
Actually, the 20mm f/1.8 offers essentially zero usable exposure benefit over a 14mm f/2.8. Using the "Rule of 500" yields a maximum exposure of something like 36 seconds for a 14mm lens, while a 20mm lens is limited to 25 seconds. That's about half a stop lost, versus just over one stop gained by the difference in apertures. Net...about half a stop, which is not a fair trade for the loss in field of view. And for high resolution cameras, like the D850 and Z7, most successful night sky photographers are using more like a Rule of 300. I personally try not to exceed 25 seconds at 14mm with my D850.
Apr 5, 2021 23:59:30 #
KenProspero wrote:
Living in an imperfect world, where one makes trad... (show quote)
Ken, just to help give some perspective when working with astrophotography, here are the approximate angles subtended by the following objects in visible light. Some data on deep sky objects gives their astrophysics size (including uv and/or ir light in addition to visible light) used by scientists with sensors covering all of those ranges.
Moon (and Sun) 1/2 degree
Jupiter (largest size at aphelion) 50 arcsec. ~ 1 arcmin. = 1/60 deg.
Andromeda 1 1/2 deg. [most of us will see it closer to 1 deg. as will our cameras]
Sources: https://er.jsc.nasa.gov/seh/math30.html
https://nssdc.gsfc.nasa.gov/planetary/factsheet/jupiterfact.html
https://noirlab.edu/public/images/noao-andromn/
--Richard
Apr 6, 2021 07:54:23 #
larryepage
Loc: North Texas area
profbowman wrote:
Ken, just to help give some perspective when worki... (show quote)
While this is good information, these objects are not what we are shooting at night with our wide angle lenses. We are shooting the galactic core, plus some item (or items) of interest in the foreground, or perhaps the entire arch of the Milky Way, again with some items of interest in the foreground or perhaps the midground. It's wide view photography, not telescopy, in most cases.
Apr 6, 2021 08:11:29 #
Thanks for all the great advice. It is much appreciated.
Larry is correct, on my coming trip, I'll be shooting the Galactic Core, and if I find an interesting foreground, star trails.
Larry is correct, on my coming trip, I'll be shooting the Galactic Core, and if I find an interesting foreground, star trails.
Apr 6, 2021 08:36:04 #
profbowman wrote:
Ken, just to help give some perspective when worki... (show quote)
For the person interested in a telescope under $1000. I have a F5, 80 mm refractor, moon just fits nicely in camera. Andromedia fits pretty well in longest axis of camera sensor. Jupiter is just big enough to discern some banding and Saturn the rings. Mars was just an orange fuzzy ball. Of course, with visual you can make objects larger with eyepieces, but not increase the observing time to get more light. Without long exposures, many objects barely show up at all even with 10 sec. time.
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