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Subject: "Beginning Night Sky Questions" Previous topic | Next topic
MarcG19 Registered since 16th Apr 2009Tue 13-Nov-12 08:07 AM
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"Beginning Night Sky Questions"
Tue 13-Nov-12 11:47 AM by MarcG19

Arlington, US
          

Hello,

I've started to dabble in photographing the night sky (not much success as of yet ), and have a few questions.

-I've heard contradictory advice from a brief google search, but it seems that some recommend that in order to NOT get stair trails, you can use shutter speeds of between 20s-1min. In my limited experience, if I don't set it to 10s, then I will have a star trail if I look at it at 100%

- do you all recommend NR to be "on" on the D90? Also, what tradeoff do I make on that generation of camera between ISO and noise?

-finally, I've been dabbling with an Olympus OM-D and a D90.

I've found the OM-D very difficult to work with (electronic viewfinder means that Venus is the darkest thing I can use for composition, and my fixed 24mm equivalent lens is sometimes insufficiently wide. ETA: landscape is invisible, and composition must be done by a painful "WAG and adjust" process).

In contrast the D90 is merely difficult to work with (DX viewfinder troublesomely dark. but IIRC at least Sirius and the brighter stars in Orion can be made out if you squint hard, and know that they're there. ETA: Landscape is only marginally more visible)

Are FX viewfinders easier to do moon-or-starlight only compositions with? Night photography won't be my only factor in format choice, but I am at a purchasing crossroads and am trying to balance m4/3, DX and FX's strengths (thus far, m4/3 has generally been winning in my calculation - but that's for a separate thread).

Cheers,

Marc

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"90% of my best life's work could have been made with a manual body, a 24mm lens, and a telephoto zoom in the 80-200 range"
- Galen Rowell
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polardan Registered since 30th Sep 2012Tue 13-Nov-12 09:53 AM
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#1. "RE: Beginning Night Sky Questions"
In response to Reply # 0
Tue 13-Nov-12 10:07 AM by polardan

Gisborne, AU
          

Here's a quick one. D700, 20mm lens, ISO 4000. F2.8. 30 second exposure.

I can't help you with the D90, sorry.

There is a lot of trial and error in getting the composition correct. However the sky doesn't tend to move away too quickly! In this shot, I was able to shine a torch on my boy to help compose (then set the timer and scramble up to join him) , but still needed several shots to get it all level. It was a absolutely pitch black otherwise (new moon, middle of the Australian desert), and stars were not really visible through the D700 viewfinder.

How much star movement depends on the time and the focal length. There are many on here far more educated than me on the subject so I won't go into it. But basically wider angle, less star movement, longer exposure possible.

The blurred stars at the top of the image are caused by the lens. Stopping down to F8 should prevent this, which I will try next time.

I have found that adjacent star images (with the same settings of course) join very well in panorama programs and I did this to get rid of the blurred stars in the corners of images.

The other thing you might look into is image stacking. Basically several photos taken consecutively, then blended by a program that realigns them.

https://fbcdn-sphotos-c-a.akamaihd.net/hphotos-ak-ash3/549569_10151003297916537_923056482_n.jpg

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GiantTristan Silver Member Nikonian since 08th Jan 2006Sat 17-Nov-12 05:08 PM
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#2. "RE: Beginning Night Sky Questions"
In response to Reply # 0


Stamford, US
          

I like to use captures of the Milky Way to assess the quality of a lens. Though I am by no means an expert in Astro Photography, there are a few point that might be of interest to you:
- Most lenses don't have an infinity stop. It is therefore mandatory to establish the correct infinity setting for your lens by focusing on a far away subject during day light.
- The maximum exposure time to prevent appearance of star trails depends
on the quality of your lens. If you get blurry star images, the trails will be hidden in the blur. The direction in which you shoot is also a factor. For example, the Polar Star will not exhibit trails even at long exposures.
- The longer the exposure, the more stars you will see.
- If you only see few stars at edges of your picture, your lens exhibits significant corner softness.
- The Milky Way has a reddish hue when photographed, quite different to its appearance to the naked eye, since we don't see colors in low light.
- The best results you will get using a good wide angle lens at a large aperture and high iso. If you use noise reduction, the weaker stars will disappear.
- As an example I attach a capture taken with D700, Zeiss 25/2 @2.0, iso 3200, tripod, mirror up. Exposure was 8s (you can verify this by counting the flashes of the anti-collision lights of the plane; the frequency of the flashing in 1/s).


Tristan

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Attachment #1, (jpg file)

  

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MarcG19 Registered since 16th Apr 2009Mon 19-Nov-12 12:12 PM
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#3. "RE: Beginning Night Sky Questions"
In response to Reply # 2


Arlington, US
          

Thanks, Gentlemen, for the tips.

Also, for others who might be reading, google searches came up with this article - very interesting, though obviously not Nikon related.

http://www.stark-labs.com/craig/articles/assets/3CanonDSLRs_ATT09.pdf
http://www.cambridgeincolour.com/tutorials/night-photography.htm

Of note, unlike the way I would have guessed, ISO 200 may not be the best point for any digital due to signal to noise ratios being best at higher ISOs (ISO800-3200 depending on camera, if I'm reading the stark labs scientist's article right).

Cheers,

Marc

--------------------------------------------------------------------------------------------------------
"90% of my best life's work could have been made with a manual body, a 24mm lens, and a telephoto zoom in the 80-200 range"
- Galen Rowell
-----------------------------------------------------------------------------------------------------

  

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