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Night sky photos and shutter speed.
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Jun 26, 2018 19:14:42   #
waynetgreen
 
On a recent vacation I had some perfect dark skies. Nikon D750. 16mm wide angle. Full manual at 30 sec shutter. Resulting photos looked great but under high magnification I did notice some star trails. My question: Is there a standard shutter speed that eliminates the trailing? I completely understand focal length will produce different results. My line of thinking is that focal length won't matter when images are enlarged to the same size.
Thanks

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Jun 26, 2018 19:21:18   #
Gemeader
 
I’v Tried to hold my shutter speed to below 15” with around twenty mm lens. Manual focus is important as well. This Fall, I’ll be in the four corners area. Plenty dark. I’ll See what I can get.

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Jun 26, 2018 19:39:52   #
repleo (a regular here)
 
waynetgreen wrote:
On a recent vacation I had some perfect dark skies. Nikon D750. 16mm wide angle. Full manual at 30 sec shutter. Resulting photos looked great but under high magnification I did notice some star trails. My question: Is there a standard shutter speed that eliminates the trailing? I completely understand focal length will produce different results. My line of thinking is that focal length won't matter when images are enlarged to the same size.
Thanks


Use rule of 500. Divide 500 by the 'apparent' focal length of your lens. eg 16mm (crop?) = 24mm 'apparent'. 500 divided by 24 = 21 seconds. The trails you are seeing may be 'coma' tails or distortion. These are a function of your lens not your exposure. Rokinon lenses seem to have very good coma performance.

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Jun 26, 2018 20:27:17   #
Gene51 (a regular here)
 
waynetgreen wrote:
On a recent vacation I had some perfect dark skies. Nikon D750. 16mm wide angle. Full manual at 30 sec shutter. Resulting photos looked great but under high magnification I did notice some star trails. My question: Is there a standard shutter speed that eliminates the trailing? I completely understand focal length will produce different results. My line of thinking is that focal length won't matter when images are enlarged to the same size.
Thanks


The 500 rule -

https://lifehacker.com/follow-the-500-rule-to-take-the-best-pictures-of-the-1790638135

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Jun 26, 2018 21:50:45   #
martinfisherphoto
 
Just to note you guys shooting JPEG and using Nikon cameras. I found if the In Camera Sharpening Setting is set above +5 it will affect the stars. I turn this feature off when I shoot in JPEG and star shooting...... I also turn this feature off when shooting night scenes like bridges that have night lamps along them.

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Jun 26, 2018 22:42:00   #
rgrenaderphoto (a regular here)
 
repleo wrote:
Use rule of 500. Divide 500 by the 'apparent' focal length of your lens. eg 16mm (crop?) = 24mm 'apparent'. 500 divided by 24 = 21 seconds. The trails you are seeing may be 'coma' tails or distortion. These are a function of your lens not your exposure. Rokinon lenses seem to have very good coma performance.


Like every other "rule," this is just a starting point. The 500 rule on a Nikon D850 with a Sigma 24 mm f/1.4 ART lens gets star movement. Play around with your settings, keep the ISO between 3200 and 1250, see what works best.

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Jun 27, 2018 05:47:40   #
mborn
 
repleo wrote:
Use rule of 500. Divide 500 by the 'apparent' focal length of your lens. eg 16mm (crop?) = 24mm 'apparent'. 500 divided by 24 = 21 seconds. The trails you are seeing may be 'coma' tails or distortion. These are a function of your lens not your exposure. Rokinon lenses seem to have very good coma performance.



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Jun 27, 2018 07:17:42   #
66mikeg
 
If you enlarge the image enough you will always get star trails until you reach the resolution limit of your sensor, the only way to avoid these is by using a guided mount with software such as PHD (Push Here Dummy). This will move the mount and the camera in the apparent direction of the star(s) when it detects that the image is drifting to the next pixel.

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Jun 27, 2018 07:21:55   #
gwilliams6
 
rgrenaderphoto wrote:
Like every other "rule," this is just a starting point. The 500 rule on a Nikon D850 with a Sigma 24 mm f/1.4 ART lens gets star movement. Play around with your settings, keep the ISO between 3200 and 1250, see what works best.


Some recommend you make that the 400 rule to be on the safe side for no star movement. Experiment with your camera because the different image sensors capture stars differently. Lens differences will affect coma.

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Jun 27, 2018 08:42:53   #
repleo (a regular here)
 
gwilliams6 wrote:
Some recommend you make that the 400 rule to be on the safe side for no star movement. Experiment with your camera because the different image sensors capture stars differently. Lens differences will affect coma.


True. I should have said the 500 rule is the maximum exposure time. It is a pretty old 'rule'. With the high ISO capabilities of newer cameras, '400 rule' would be safer.

If you really want to get into it, the Pentax K-1 has a setting that uses the vibration reduction system to move the sensor to track the stars. Sounds good on paper!

I just came across this interesting info at https://petapixel.com/2014/01/29/picking-great-lens-milky-way-photography/

" Note that differences in sensor resolution, pixel size and even the direction you point your camera in the night sky will change how the rule works. APS-C cameras and cameras with higher resolutions sensors need shorter focal lengths to achieve similar shutter speeds without star trailing and the rule becomes something closer to a “300 Rule” for APS-C sensors the guide below. Basically, it differs by camera.

Also, pointing your camera toward the celestial equator line will cause more star trailing than near the poles due to the larger arc length swept by the stars in that portion of the sky. The important thing for you to do is to generally determine what maximum shutter speed will work best for your particular camera and lens combination. Start with the recommendations here for your lens and then adjust accordingly. "

Also good article on good coma lenses
https://www.lonelyspeck.com/lonely-specks-ultimate-list-of-best-astrophotography-lenses/

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Jun 27, 2018 09:08:27   #
Algernon
 
After doing a lot of experimentation with my camera / lens combination (Sony 6300 APS-C, Rokinon 2.0 12 mm), I have found that I can achieve the best results with a 20 second maximum exposure to avoid coma (at ISO 1600). That is essentially a "400 Rule".

I sometimes use 15 seconds ("300 Rule") but then I have up increase the ISO to gather enough light which increases the noise.

I have decided that having stars that are slightly oval upon magnification is better than dealing with the noise.

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Jun 27, 2018 10:52:19   #
waynetgreen
 
Thanks everyone for the information. Lots of knowledge in this group!

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Jun 27, 2018 15:18:14   #
bwana (a regular here)
 
waynetgreen wrote:
On a recent vacation I had some perfect dark skies. Nikon D750. 16mm wide angle. Full manual at 30 sec shutter. Resulting photos looked great but under high magnification I did notice some star trails. My question: Is there a standard shutter speed that eliminates the trailing? I completely understand focal length will produce different results. My line of thinking is that focal length won't matter when images are enlarged to the same size.
Thanks

Depends how picky you are!? If you're using a tripod, there will always be star trails regardless of shutter speed. 30 sec. exposures with a 16mm lens is under the Rule of 500 exposure of 31.25 sec. so you're seeing minimal star trailing.

bwa

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Jun 27, 2018 22:42:08   #
lrjames
 
No longer than 20 seconds and I so shouldn't be any higher than 6400 but that depends on your camera

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Jun 28, 2018 10:17:10   #
Silverman
 
repleo wrote:
Use rule of 500. Divide 500 by the 'apparent' focal length of your lens. eg 16mm (crop?) = 24mm 'apparent'. 500 divided by 24 = 21 seconds. The trails you are seeing may be 'coma' tails or distortion. These are a function of your lens not your exposure. Rokinon lenses seem to have very good coma performance.


Wow, never heard of the "500" rule, so, my understanding is, 16mm x1.5 (nikon crop)=24mm, then 500 divided by 24=21 sec. shutter speed, correct?
Would this be good rule for Fireworks too?

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