The Night Sky

D700 & 14-24mm f/2.8

46 Seconds @ f2.8 ISO 1600


32 Minutes @ f/8 ISO 200

 

Nice stuff Jeff.

Our skies have been too gray and rainy lately to get anything this good. Think you can send some weather to the Northwest corner of the "sunshine" state.

 

Great shots!! ; I like 'em.

 

These are beautiful. ; I like the first one where you picked up colors in the night sky.

How do you calculate the exposure, Jeff? ; Did you manually handle the shutter or can you set up the D700 for very long exposures?

 

VERY NICE!

 

Thanks all-

Scott- taken in bulb mode with a remote cable release (which latches- I was inside watching television for the long exposure ; )

 

So any camera with bulb mode can do those long exposures? ; Never tried that.

Although living in the Northeast, I might find my camera frozen if I leave it outside for that long!

 

Awesome! ; Nicely done Jeff. ;

There is actually a way around that problem. ; Moose Peterson wrote a tutorial on his website:

http://www.moosepeterson.com/digitaldarkroom/lessons/lights_of_the_Heavens.pdf

If your camera has a built in intervalometer (or if you have a Nikon with a 10-pin connector and the MC-36 Multi-Function Remote) you can shoot a series of shorter images and then put them back together using one of several methods. ; That way, you still get the really long star trails but you remove the noise and sensor bloom issues.

 

Canon has a timer remote that can be used to take a series of pictures too. ; I've used it, the only problem (I don't know if the Nikon devices have this) is that at a minimum there has to be one second between exposures while the cameras could manage much tighter timing. ; Viewed full resolution even a single second gap showed up in my star trails, but it mostly went away when shrunken down to typical web viewing sizes.

There's another upshot to using the process of taking many shorter exposures and joining them together. ; It minimizes the appearance of light pollution. ; With the proper blending mode (I manually stacked them in photoshop, there the key is using the right blending mode, but I understand those modes so little that I don't even know which one I used, I just try different ones until I get the result I want) what PS does is only stack the stuff that's different. ; So the general image of any ground detail in the image as well as the sky glow remains basically static and isn't added together, but the star trails change and so they're all put together.
It sounds like the Startrails program referenced in that PDF does this automatically, I'm sure it also makes the process practical with larger numbers of pictures. ; My startrail test was supposed to be a bit less than an hour, but my camera started accumulating dew at about the half hour mark, everything after that was lost because of how blurry the image got.

I've mentioned this before and I'll mention it again, it seems that there's a little understood optical effect where point sources of light (which is how stars will appear when looked at anything other than a fairly powerful telescope) don't respond to aperture changes in the same way that area sources do. ; Whereas area sources respond as you'd expect, one stop aperture change results in one stop more or less light, point sources change less. ; The formula for the change requires taking the aperture and focal length into account, I don't remember what it was though.

The upshot of this is supposed to be that if you use a narrower aperture you'll reduce the appearance of light pollution and haze and whatever but the stars should be reduced in brightness less.


One other thing, I looked up the rule of thumb formula for how long you can make your exposure and still get sharp points of light instead of blurs for stars, if you're going for sharp stars versus a trail. ; The formula I got was 600 divided by your focal length, the result being the number of seconds you can leave the shutter open for. ; But I don't think this is near as cut and dried a matter any more. ; The formula should depend on the resolution of your sensor or perhaps more appropriately the resolution that you expect to use your results at. ; I should specify that I mean pixel density, a full frame camera of a higher total resolution but with the same sized pixels should work out the same. ; Mind you many online sources disagree with me on that last point, but so far no matter how many times I think it through I'm convinced that sensor crop factor shouldn't effect this at all.

 

There is an awesome article on night photography at http://www.availablelightimages.com/articles/technical-writing/night-light

Erich

 

Okay, been a while since I embedded an image from offsite, but I wanted to play with this expando thing even if it's not entirely appropriate for this particular image.

Taken in Northern Minnesota, in the Boundary Waters Canoe Area Wilderness. ; Even that far away, under skies that should be very, very dark, I was still not safe from light pollution. ; But it was dark enough to do this. ; If I'd had some sort of tracking mount, or even the popular crude substitute, the barn door tracker (a popular easy to build mount that will allow you to compensate for the Earth's rotation for limited lengths of time), I could have gotten more. ; Note the satellite track near the lower right corner.

11mm F2.8 25 seconds
http://www.flickr.com/photos/33201257@N00/4364278722/#
[expando]http://farm5.static.flickr.com/4067/4364278722_c3f20ba1e7_o.jpg[/expando]


Just to sorta prove my point.. the available light images guide suggests using a rule of thumb of dividing 500 by your focal length to get the maximum time the shutter can be open in seconds, as a conservative version of the 600 rule. ; It still didn't work, I can see elongation of the stars, they're starting to blur if I look at it full resolution even though I'm clear of the 500 rule. ; At this res.. maybe you can see it a little bit.


There's a trick I've since learned where I could have illuminated the tree for a brief period of time with a flashlight so that it was visible as more than just a silhouette. ; And now that I look at it I realize it looks upside down.. it's actually mostly straight up, but the wide angle made the tree look upside down.

I've joined my local astronomy club, they have a private dark sky site that I have access to now. ; I was there once last year, but it was so cloudy that I couldn't really see how much milky way detail I could get. ; I'll try again this year, once it warms up. ; It isn't likely to be this dark, though.

 

Nice shot Dan- and thanks for all the tips. ; I am looking forward to trying again soon.