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Author Topic: Has anyone shot long exposures of the night sky with a H3DII-39?  (Read 1331 times)
Gel
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« on: December 29, 2012, 06:13:23 AM »
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Now the wedding season is over I would test this myself...but we've had nothing but cloud cover for two weeks here in the UK.

I don't want trails, just the stars however it's something I've not tried as yet with MF
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BartvanderWolf
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« Reply #1 on: December 29, 2012, 08:42:14 AM »
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Now the wedding season is over I would test this myself...but we've had nothing but cloud cover for two weeks here in the UK.

I don't want trails, just the stars however it's something I've not tried as yet with MF

Hi,

If you want sharp stars then you need either:
  • a short enough exposure time (e.g. max exposure time ~= 1000 / focal length) to avoid the apparent movement of the stars to become more than 1 pixel (depends on focal length and sensel pitch and orientation to the sky from your geological position),
  • or use a tracking device which moves the camera at the same pace as the stars, thus keeping them stationary, (but will blur the landscape),
  • or resort to a software generated starry sky for your location and time, and make a montage.

The problem with short enough exposure times, especially when you use longer focal length lenses (which magnify the movement), is that you won't get enough stars to show up, especially when you shoot during dusk or dawn, or when there is a lot of light pollution.

To improve the number of stars you can record during a short exposure, you can register multiple exposures and add them in a composite, although that won't solve the lightpollution issue, and you'll have to mask out the terrestrial elements.

As for a software solution (when the clouds persist and you cannot shoot anyway), you could use a program like Stellarium. You can stitch multiple segments of screen captures of the stars to achieve the same Horizontal field of view (HFOV) as you camera covered for the terrestrial elements, and by zooming in in the software, you can achieve a pixel resolution to match you camera's sensor. So if your sensor has a horizontal resolution or e.g. 7304 pixels, your stitched image should at least have that resolution. That means that, depending on your screen resolution (e.g. 1920 pixels) and a bit overlap for stitching, you could need e.g. 5 horizontal screen captures where each screen has roughly 1/4th of of the HFOV of the final image, and some 4 rows (assuming Landscape orientation).

Cheers,
Bart
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FredBGG
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« Reply #2 on: December 29, 2012, 01:13:33 PM »
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A bit OT, but I know you have Canon too....
If you like astrophotography take a look at the EOS 60Da.
It's a special edition of the 60D that is optimized for astrophotography.
It sees colors other digital cameras simply do not see.

Comparisson:



I have a friend that stitches with this camera and produces incredible 40x120 inch prints.

Also did you see this post?

http://www.luminous-landscape.com/forum/index.php?topic=73505.0

But be careful getting into Astro photography... there is a whole world of addictive gadgetry  Wink

Last two nights were incredibly clear here.
When we get dry cold clearing winds the sky just lights up.
I went for a Night Hike with my dogs up to a mountain peak and it was swarming with
Astro photographers. I didn't take a camera, I just soaked it in.

I even go night surfing and kitesurfing on nights like this.
« Last Edit: December 29, 2012, 01:31:24 PM by FredBGG » Logged
Paul2660
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« Reply #3 on: December 29, 2012, 01:33:22 PM »
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I looked at the 60Da for my night work but from what I could tell it's more suited for work with a telescope where you see the nebulas and the like. 

IMO the 60da for standard star work is also limited by the 1.5 crop factor which greatly limits your view of the sky. 

I prefer the full frame Canons for non telescope night work.

A few other tricks I learned is you need to have the lens as wide open as possible F2.8 or better as you will pull in a lot more stars.  30 seconds is about as long as you canto before you start to see trails.  It is a neat way to shoot as you can capture constellations I the night sky.  Also work with the moon if possible as it will help to mask the standard amber color to the sky you get from light pollution.   Moonlight will give you a nice blue color to the sky.  You will have to work at a higher iso maybe 400 or 800 which tends to rule out MF. 

Paul
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Paul Caldwell
Little Rock, Arkansas U.S.
Photography > http://photosofarkansas.com
Blog> http://paulcaldwellphotography.com
Gel
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« Reply #4 on: December 29, 2012, 01:47:16 PM »
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Thanks Fred, but Paul kinda nailed it.

I'm looking to use the 35mm and a long exposure. Probably overlaying them via software.
Maybe one day when I have time I'll go the scope route but I'm thinking of going up to the Teide observatory for some wide view with the Canon for Timelapse. (With the Hassy for stacked shots).

I'd probably invest in a timelapse Dolly before getting the 60Da
« Last Edit: December 29, 2012, 03:38:13 PM by Gel » Logged

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FredBGG
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« Reply #5 on: December 29, 2012, 02:01:41 PM »
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..
« Last Edit: December 29, 2012, 02:50:56 PM by FredBGG » Logged
jsiva
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« Reply #6 on: December 31, 2012, 10:52:51 AM »
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Take a look at http://www.sanjeevsivarulrasa.com

My twin.  Does pretty much all astro work.  I know he uses a lot of different cameras ranging from modified 40D, 5DII, CCD etc...

Horses for courses ....
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Brian Hirschfeld
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« Reply #7 on: December 31, 2012, 07:58:36 PM »
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I take a short look at astrophotography with MFDB's in my PhaseOne IQ180 review here http://brianhirschfeldphotography.com/2012/01/14/phaseone-iq180-a-love-story/ and I previously owned the H3Dii-39ms which I reviewed here while I do not discuss long exposure in my review of it here http://brianhirschfeldphotography.com/2011/12/07/hasselblad-h3dii-39ms-and-80mm-f2-8-lens-2/ I can say from my own experiences that the camera and its sensor are not made for exposures more then a minute (which is pushing it at best). Excessive heat noise will develop. I know in astrophotography that a dark shot is taken to record the head noise at the same exposure (picture taken with the lens cap on for the same amount of time as the original exposure) and then they are composited together to subtract the noise. However, I question how effective this could be with a MFDB that is not purpose built for long exposures, like the P45+ which can go for up to 60 minutes (http://www.digitaltransitions.com/page/phase-one-plus-series) it does a sort of dark slide process where it takes the exposure for 60minutes and the processes for another 60minutes to attempt to remove this noise. The Hasselblad does not offer either of these services (if you can call it this) provided by the P1...
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www.brianhirschfeldphotography.com / www.flickr.com/brianhirschfeldphotography
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Paul2660
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« Reply #8 on: January 01, 2013, 11:15:41 AM »
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I believe that the "dark frame" is mainly to remove stuck pixels, which are most often red, green or blue but sometimes show as white.  From my usage, the stuck pixels seem to get worse as the camera is used and heat is generated, especially with longer exposures.  Humidity will also make the effect worse.  In the older days before cameras had "long exposure noise reduction" as an option, the technique involved  taking a shot of with the lens cap on after you were done with the shot.  You then could use several software programs that are designed  to blend the dark frame and the actual frame, and blending the stuck pixels out. You can also do this in photoshop with a layering technique but I never found it to work as well as the software programs.   To me the name "long noise or long exposure noise reduction" is a bit misleading as the true digital noise is not really worked on that much, only the stuck pixels. 

The P45+ from my usage did a very good job here, but as Brian pointed out, it has to take a 2nd exposure as long as the first up to 60 minutes.  And getting to 60 minutes really required ideal conditions, outside temp not higher than 69 degrees F  and very low humidity.  It also pretty much took the life of one battery, i.e. two 1 hour exposures.  And if you calculated wrong, and the battery ran out on the dark frame, then the entire sequence was no good.  Still an amazing solution and truly a one of kind for MF long exposures.

The main reason I switched to 35mm for night work, is that you can most times turn off long noise reduction, and stack exposures, which gives you a lot more detail in the night sky.  It also gives a lot more to work with in the landscape part of your shot as over an hour conditions will most times vary.  Wind and clouds, wind more than anything can ruin the shot.  You will pick up some stuck pixels, but if you use LR and shoot raw, most times the stuck pixels will be mapped out by LR.  If you shoot as jpg, then you have to revert to the manual method to remove the stuck pixels. The other thing to remember is that most times on each shoot, you will get a different set of stuck pixels so if you take the "shoot a manual dark frame" you need to remember to do it each time.  Enabling "long noise reduction" will create gaps due to the necessary dark frame (when stacking) and also the camera will eventually buffer out (Canon) Nikon has no buffer and works just like Phase One i.e. shoot one, wait one for the same time.

Again, this is only in regards to night shooting mainly to work with stars and sky.  I realize that there are many other applications, studio or daytime long exposures were the P45+ is a great solution. 

Paul


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Paul Caldwell
Little Rock, Arkansas U.S.
Photography > http://photosofarkansas.com
Blog> http://paulcaldwellphotography.com
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