30 minute exposure [pics]

[Timkat]

We've all seen the star trails pics before but I thought I may do it again by just releasing the shutter and letting it run out of time all on its own 30 minutes later it had finished with the shot. Another 20 minutes later the battery went flat in the middle of NR. Anyway here is the result...



18mm, manual focus at infinity, f 3.5, 1800 seconds @ iso 400. Image shot in raw, white balance was manually set in ACR. Did a rather rough job in removing the CCD burn in CS2. No noise reduction in post work, just smart sharpen (almost too much)

The trees were not visible with the naked eye but clearly enough light pollution from the distant house provided illumination.
And for interests sake a 100% crop.



Cheers,
Tim
http://www.hillsrain.com
http://weather.saint.net.au/

 

[Tornado7]

your shot is beautiful! I like the composition with the circled trails around the one star.

everytime I try exposures longer than 10minutes I get these ugly pink noise in the top left corner... any idea?

 

[drejc]

it looks like this kind of pictures aren't so bad compare to canon which is better in long exposures.

what do you think?

 

[Lysias]

your shot is beautiful! I like the composition with the circled
trails around the one star.

everytime I try exposures longer than 10minutes I get these ugly
pink noise in the top left corner... any idea?

Did you switch on thew noise reduction function? (Shooting menu, second option: Long exposure NR)

Philip

 

[RRudeski]

Would you mind sharing the method you used to get rid of the amp glow, or ccd burn? I took almost the same shot last night, but only a 5 minute exposure, and trashed all the shots due to the pinkish overall glow. Otherwise, I thought they were nice shots.

Also, someone here mentioned taking several shorter exposures and stacking them in PS. What is the max exposure time and min time between exposures in order to avoid the amp glow problem?

Thanks in advance.

Rob

 

[Timkat]

Cheers mate

The pink glow is amp glow/ heat on the CCD. Turning on noise reduction in the menus removes it. Unless your battery goes flat like me ;-) You can PP it out but its rarely as good. Here's a good example of the amp glow.
ISO 800 @18minutes



Cheers,
Tim

 

[Timkat]

I think the canons are still the long exposure kings, but the D70 (s) does not disgrace itself, far from it! I often wonder how the D2x fares on super long exposures? The D50 has a redisgned sensor and is supposed to not show up amp glow until 15 mins or thereabouts.

 

[Timkat]

Would you mind sharing the method you used to get rid of the amp
glow, or ccd burn? I took almost the same shot last night, but only
a 5 minute exposure, and trashed all the shots due to the pinkish
overall glow. Otherwise, I thought they were nice shots.

I used the colour replacement tool in PS and also selected small portions of the brightest parts of the burn with the lasso tool, feathered the selection and adjusted with curves. You can sometimes apply a selective colour to the selection as well dependimng on the circumstance. No matter how hard you try though you cannot bring back the detail lost behind the burn.

Sometimes though the image composition can hide the burn such as this which was 2 mins. The lightning active storm above blended nicely with any CCD burn which may have been present

Also, someone here mentioned taking several shorter exposures and
stacking them in PS. What is the max exposure time and min time
between exposures in order to avoid the amp glow problem?

Now thats a good question. I have never tried stacking. I guess it depends on environmental conditions. (temp) a nice cool night may let you run into a few minutes without problems??? Can't give a good answer here sorry

Cheers,
Tim

 

[Roland Wooster]

I've never seen such a good example of star trails before. The star in the middle that appears not to be moving (yeah I know it's us that's actually rotating) is that the North Star?

How far north were you when you took this picture? I'm wondering if you're further north because I've never seen anything other than an arc before, unlike the full circle you have.

Thanks,
Roland

--
Gallery at http://www.rolandwooster.com

 

[egrivel]

Cheers mate
The pink glow is amp glow/ heat on the CCD. Turning on noise
reduction in the menus removes it. Unless your battery goes flat
like me ;-) You can PP it out but its rarely as good.

I'm wondering -- is this affected by ambient temperature? Would it be better to take these kind of pictures in the winter?

Best,
Eric

 

[Timkat]

LOL mate, not very far north at all. Quite the opposite actually! Thats the sky as viewed from Sth OZ near the little city of Adelaide. I am lucky enough to have little light pollution from the city. The night skies are even better, actually jaw dropping in the desert counrty up north (near lake Eyre/ Maree etc etc)
Cheers,
Tim

 

[Christoph S.]

...that the pic is not over-exposed with f 3.5 and 30 min.

 

[yirmon]

Nice shot Tim. Star trails always amaze me and this one is no exception. I keep meaning to try this technique, but the skies are never clear enough here!

Cheers,

John
--
http://johnwaller.co.uk
http://john.stuwee.org
http://thedailyexposure.blogspot.com

 

[Timkat]

...that the pic is not over-exposed with f 3.5 and 30 min.

Possible for the trees?? But certainly not the skies IMO. You can see the white haze of the milky way running through the centre of the image. Bumping the ISO to 1600 and 1-2 min exposure on a dark night and the milky way pops out in all its splendour!
Cheers,
Tim

 

[dad_of_four]

You can
see the white haze of the milky way running through the centre of
the image. Bumping the ISO to 1600 and 1-2 min exposure on a dark
night and the milky way pops out in all its splendour!

All those millions of years ago, those photons burst forth from the milky-way, and traveled through the vacuum of space, only to be captured by your tiny slice of silicon we call a CCD. Pretty amazing. Treat those photons with care

DO4

 

[Tornado7]

I always thought this glow has to do with ISO settings... just as your battery ran flat during NR, I switched the camera off because I wanted to go to bed ;-) still had the shot but withour NR.

I'll try this next time...

thanks!

 

[Roland Wooster]

OK, far south then. None the less, my real question is how did you find a star that the earth's rotation is in linear axis with, and thus shows up as a center point of the image which everything else is rotating around?

Is it easier to achieve than I'm thinking and you just pointed the camera upwards or are you an astronomer and knew what to aim for, or are you extremely lucky?

Thanks,
Roland.

--
Gallery at http://www.rolandwooster.com

 

[Jon Read]

Really nice shot, Tim.

For interest's sake I ran your 100% crop through HotPixel ( http://www.redpawmedia.com/hotpixel.html ) with threshold of 10 and no other options.

Original:



Processed:



Seems to have removed the worst of the noise!

Cheers,
Jon

 

[tdkd13]

The glow is affected to a certain degree by temperature. The cameras we make at work are cooled to -10 to -30 degrees C by use of a peltier cooler for this reason and to reduce noise. These are very expensive (up to $75K) highly calibrated cameras for diagnostic, R&D, and quality control work. I dont even think they are capable of 30 minute exposures though, they are designed to take relatively long exposures (up to a minute) but take several thousand in a row.
Ted

 

[Timkat]

What a great little plugin! Thanks Jon!!!

It worked very well over the trees, but did remove a little of the star detail. Used with layer masks it really does the job.