A Shot in the Dark

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Tim Seaver

Tim Seaver

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Aurora Boulderalis
KatahdinAtNight.jpg

Katahdin from 1-95, 10:30pm

This was taken at a rest area somewhere on 95 at 10:30 pm. I couldn't see a dang thing, but a sign pronounced that a view was indeed there despite the darkness. So I just starting shooting in the general direction of where the "view cutout" seemed to be, taking 30 second exposures, wide open at 2.8, at ISO 6400 ( 75mm focal length). It took a about 10 exposures to "find" the peak.

Is it possible that the orange glow is from Quebec, 150 miles to the NW?

To clean up the noise from the insane ISO 6400 that the 1D can crank out, I used "Noise Ninja ", a plug-in for Photoshop that is a pretty amazing tool for reducing noise.
 
For moonrise shots, generally 1/2 second is the longest exposure you can use without showing a blur.

Using an astro motor drive isn't really an option when including fixed objects like large mountains in your starscapes. ;)

My favorite quote from the LL page Doug linked to:

For all the anal compulsives out there, here's the scientific formula for calculating star trail exposure times as quoted from Sky & Telescope...

The length l of a star's trail on the film in millimeters can be calculated from the formula


l = [tF cos (delta)]/13,750,

where t is the exposure time in seconds, F the focal length of the lens in millimeters, and delta is the north or south declination of the star.

Happy?
Click to expand...
 
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Tim Seaver said:
Using an astro motor drive isn't really an option when including fixed objects like large mountains in your starscapes. ;)
Click to expand...
Unless you like sharp stars and streaky mountains... :)

Three options:

Option 1) Take a double exposure masking out the sky (drive off) or mountain (drive on).

Option 2) Take the pic twice, once with motor drive on and once with it off. Then mask and combine in post-processing.

Option 3) Run the motor drive at half speed. This will allow up to double the max exposure without the drive.

Options 1 and 2 allow independent exposures for hill and sky.
--------------------------

Low light photography can be amusing...

Took some pics of a comet once. Didn't have an astro drive and they came out a bit streaky.

Doug
 
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DougPaul said:
600/eFL is the maximum exposure to prevent the stars from streaking unless you use an astronomical motor drive.

Doug
Click to expand...

That seems like a good rule. For the pic above (cool by the way) shot at 75mm you would have a max exposure time of 600/75= 8 sec for no star trails. Tim said he shot at 30 sec so if he had cut the exposure time to 8 sec then the star trails would be 8/30, or about 1/4 as long which in this case would be pin points like normal stars. Cool. But then he would need a camera with ISO 25600 in which case you would not be able to tell stars from noise. Either that or get a f 0.0 lens. :D

One other way is to take one 8 sec shot that is underexposed and stack it on top of itself in PS and use the layer control in "screen" or "multiply" mode (i forget which is used to lighten and I dont have PS with me right now) to lighten it up.

It is crazy that there is that much light from a city 150 miles away, huh? guess that is why they put observatories on top of the volcanoes out here - elevation, low pollution, and low background light.

Tim - way to see the shot without seeing the shot. My only suggestion would be that since you have to deal with star trails, you should make it look like you did it on purpose. Use a remote and go for a really long exposure at a lower ISO / higher f stop. Assuming you have a 1/2 hour to kill.


- darren
 
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darren said:
Tim - way to see the shot without seeing the shot. My only suggestion would be that since you have to deal with star trails, you should make it look like you did it on purpose. Use a remote and go for a really long exposure at a lower ISO / higher f stop. Assuming you have a 1/2 hour to kill.
- darren
Click to expand...
It would be great to be able to do so with a digital camera, but 30 seconds is as long as you can go, at least for now ( I am not sure how much of a "wall" this is with digital imaging, BTW) {EDIT - Whoops, that's not correct - somehow I had the impression the 30 seconds were the limit, but that is not the case.} Film would be the answer for that one. And about 4 hours to get a half-way decent trail! This was more in the name of experimentation than anything else. It is fun stuff, I love shooting after dark with digital cameras!

RainierStarscape.jpg


Mount Rainier by Moonlight, Reflection Lakes

This was with a Canon 5D, ISO 500, f4.0 at 35mm, 30 seconds.
The noise wasn't terrible, but the Ninja took care of that. Definitely try that plug-in ( there is a stand-alone app as well)!
 
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Tim, I absolutely love the second image of the mountain and night sky. I really need to get out there more at night, and this is inspiring. Hey, the mountain peak is centered! How naughty ;)

The screen on my 300D shows night images to be lighter than they are when I view them on the computer. I haven't tried my new 400D at night yet. Anyone notice this, and any tips for dealing with it, without formulas and such? Thanks much!

happy trails :)
 
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