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07-29-2009, 05:20 PM   #1
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Dark sky with lots of stars... how to picture that???

Hi,

Last night I was in a remote area in the mountains... At midnight the sky was clear and we could see the stars... lots and lots of them. We tried to make a shot of this with a K200D but I guess we did something wrong...

What should be the exposition time, iso, f, anything??? to make this shot???

Thanks!


Annie
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07-29-2009, 06:59 PM   #2
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Here's my recent attempt:


The "Sagittarius Star Cloud." Milky Way near Scutum, with M11, M16, M17, M24, and M25.

K10D, ISO 1000, A-50mm @ f/1.7, 8 seconds
07-29-2009, 09:57 PM   #3
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QuoteOriginally posted by BlueEye Quote
Last night I was in a remote area in the mountains... At midnight the sky was clear and we could see the stars... lots and lots of them. We tried to make a shot of this with a K200D but I guess we did something wrong...

What should be the exposition time, iso, f, anything??? to make this shot??
Here's the simple answer:

If your picture cme out too dark you need more exposure. If your picture came out too light, you need less exposure. If you don't know how to increase or decrease exposure, you need a book on exposure - one that explains how aperture, shutter speed, and ISO relate.

Eventually, it might be possible to learn enough to be know ahead of time what exposure would be appropriate for this shot, or to know how to use the camera's meter to get a reasonable answer. But if you know the basics of exposure, it will always work to take a test shot then increase or decrease exposure as necessary. Not just as a method for taking starry night photos, but as a method for taking *any* photos.
07-30-2009, 04:51 AM   #4
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QuoteOriginally posted by Marc Sabatella Quote
Here's the simple answer:

If your picture cme out too dark you need more exposure. If your picture came out too light, you need less exposure. If you don't know how to increase or decrease exposure, you need a book on exposure - one that explains how aperture, shutter speed, and ISO relate.

Eventually, it might be possible to learn enough to be know ahead of time what exposure would be appropriate for this shot, or to know how to use the camera's meter to get a reasonable answer. But if you know the basics of exposure, it will always work to take a test shot then increase or decrease exposure as necessary. Not just as a method for taking starry night photos, but as a method for taking *any* photos.

Ummm .... yep ?!? and ...

07-30-2009, 05:06 AM   #5
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QuoteOriginally posted by Marc Sabatella Quote
Here's the simple answer:

If your picture cme out too dark you need more exposure. .
But if you increase your exposure time, you will have star trails instead of "well" defined stars. So, instead of increasing exposure time, you might want to open up the diaphragm and increase ISO.
07-30-2009, 05:32 AM   #6
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I've tried star trails with very limited success. But I like the look of pics like the one below.

I'm thinking this is a photoshopped composite of a long exposure for devil's tower and short (no trails) for the stars. Is this guy perhaps using a star tracker (something to allow for long exposures by counter-rotating the camera as the earth rotates)?

APOD: 2009 July 29 - The Milky Way Over Devils Tower




This link has some interesting ideas about photographing stars:

http://www.ozanimals.com/blog/photographing-stars-with-kit-lens/

Last edited by theprisoner6; 07-30-2009 at 05:43 AM.
07-30-2009, 05:47 AM   #7
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the image is obviously photoshopped. the way to tell is that it has stars visible through the clouds, oops!
07-30-2009, 06:09 AM   #8
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Check out the Beginning Imaging and dSLR forums at Cloudy Nights. They do this kind of imaging all the time.

Telescope Reviews: Viewing forum: Beginning Imaging

Telescope Reviews: Viewing forum: DSLR & Digital Camera Astro Imaging & Processing

It's much more involved than a single exposure.

07-30-2009, 08:49 AM   #9
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QuoteOriginally posted by flyer Quote
But if you increase your exposure time, you will have star trails instead of "well" defined stars. So, instead of increasing exposure time, you might want to open up the diaphragm and increase ISO.
True, but note I didn't say say increase exposure *time*; I said increase *exposure*. Which can be done by slowing the shutter, opening up the aperture, or raising the ISO, or any combination. Once you've got the exposure right, then one can worry about finding the right tradeoff between these three parameters to get the kind of definition you want. I suppose it's possible that this is what the OP was up against, but without images to work from, I'm guessing the basic exposure problem needs to be solved first.
07-30-2009, 11:55 AM   #10
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Pacholka said he employs simple techniques and does nothing extraordinary to get his shots. He uses a standard 50mm lens mounted on a tripod, and points a small flashlight on nearby desirable rocks and other land features he wants to stand out in the photo.

He allowed that his digital camera has a light-gathering power that is in some instances more than 50,000 times greater than a typical daylight camera setting. Pacholka runs his exposures anywhere from a few seconds to a minute. But he doesn't consider himself a guru.

"This is something the average person could do, absolutely," he said.

Source: About Wally Pacholka

Many times the stars will show through thin cloud layers. The human eye doesn't see this, but the film or digital does.
07-30-2009, 11:56 AM   #11
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The other night, I found that 5-6 seconds was about right for minimizing star trails and maximizing exposure, with a 50mm lens. Obviously, the wider the lens, the longer you can expose before trails become apparent. I have a star drive, but couldn't be bothered to hook it up that night, since I was in the middle of town. I just wanted to see what I could do with a K10D in all the ambient light pollution.
07-30-2009, 03:55 PM   #12
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Southern Cross-


Pentax *istDs
Sigma 70-200 EX 2.8 at 70mm
Exposure - 8 seconds f2.8 (may have had 1.4x TC on - can't remember)
Tripod (funnily enough)
No flash
Camera and lens pointing up
07-30-2009, 07:44 PM   #13
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If you want to capture a lot of stars with no trails you can stack multiple images and use some special software or you could build a cheap barndoor tracker. Below is a picture of the one I built. It's a little more elaborate with the $20 rifle scope and $10 ball head - other than those two items it cost around maybe $10-$15. All you do is align the hinge to the north star, point the camera at the section of sky you want, and turn the crank 1 rpm during exposure. Longer exposures will reveal hundreds of stars you never knew were there. Cool stuff. Google 'barndoor mount'... there are several designs out there. Some simple like mine... others more complex than they need be.

-Brian


Last edited by Das Boot; 07-30-2009 at 07:53 PM.
07-31-2009, 05:38 PM   #14
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Google "astrophotography Stacking". Also, I just posted on the topic here with a link to some freeware that will help you:
https://www.pentaxforums.com/forums/689414-post18.html

Here is an example from someone on Flickr that used the stacking technique.
http://www.flickr.com/photos/mattie_shoes/816277697/

I don't have any examples using my Pentax gear yet, but I hope to soon!

Edit: Love the innovative mount Boot!

Last edited by PentaxPoke; 07-31-2009 at 07:55 PM.
08-01-2009, 03:49 AM   #15
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Interesting. How did you mount the ball head to the tracker? And does 1 rpm = one exposure?
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