Shooting Star Trails - long exposure or stacking

What method do you use to shoot star trails


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emlee

Senior Member
Mar 10, 2008
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Ang Mo Kio
#1
Hi,
I am interested to know if anyone still use single long exposures to take star trail photography. Especially on digital cam where hot pixels can be a problem.

Been reading the use of stacking in post process to combine hundreds of pictures to create star trails. Keen to explore.
EM
 

Ian

Senior Member
Feb 20, 2002
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Perth Australia
#2
Hi,
I am interested to know if anyone still use single long exposures to take star trail photography. Especially on digital cam where hot pixels can be a problem.

Been reading the use of stacking in post process to combine hundreds of pictures to create star trails. Keen to explore.
EM
Stacking works better unless you are using film where a long exposure is still the best way.

Go play with it.
 

Jan 19, 2008
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#4
To suppress the noise, stacking multiple photos with same settings will give you good result.

Normally you don't even need bulb mode, 30s exposures will do.
 

Estherfu

Senior Member
Feb 28, 2008
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www.estherfu.blogspot.com
#5
To suppress the noise, stacking multiple photos with same settings will give you good result.

Normally you don't even need bulb mode, 30s exposures will do.
arh...that will certainly reduce noise, hot spots and the number of stars captured(gets very messy when there are too many of them)
Did you leave 1 sec between shots and what focal length were you at?

esther
 

Jan 19, 2008
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#6
Steps as follows say you want an 1 hour startrail:

  1. take 120 continuous 30s exposures at proper aperture or ISO settings depending on enviroment.
  2. optional, take a dark frame using the same settings by putting on the lens cap.
  3. stack the photos
    • by Photoshop: use "lighten" mode in layer blending options, this will remove the random noise if you take enough frames; substract the resultant image with the dark frame to remove hot pixels, place the dark frame layer above the startrail layer, set blending mode to "difference".
    • use the software in the following link, it will do the job automatically, fast and straight forward.
      http://www.startrails.de/html/software.html
 

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Jan 19, 2008
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#7
arh...that will certainly reduce noise, hot spots and the number of stars captured(gets very messy when there are too many of them)
Did you leave 1 sec between shots and what focal length were you at?

esther
I borrowed a remote timer control from my friend for the Canon 50D I used for the photo, it seems compulsory to have a 1s gap between exposures.

The focal length I used was 16mm.

Actually I didn't use 30s exposures. The objective then was to capture the stars as well as the moon-lit snow mountains. It was a not-so-bright last quarter moon, so that if I want the mountains to show in in the picture, I needed to go max aperture f/2.8 and ISO3200. At f/2.8 the mountains were not focused perfectly...So I used 6 5min exposures at f/5.6 and ISO 400. By stacking 6 frames only, the noise performance doesn't improve much at all...
 

AReality

Senior Member
Jun 9, 2003
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#8
I tried both before.

Stack if the foreground light is too bright.

Basically is find the maximum length of time you can open your shutter at an apporiate f-number, I use f/4-5.6, iso 100-200. Then stack if the length of your star trails is not long enough.

But when you stack, the breaks between the lines can be seen very clearly.
So if you want exhibition quality, don't stack. Noise is a secondary issue.
 

Lolrence

New Member
Oct 15, 2006
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#9
I've done a 40min long exposure with a Canon 40d, there's a bit of noise, but that can be removed in PP.
 

night86mare

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Aug 25, 2006
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#10
I've done a 40min long exposure with a Canon 40d, there's a bit of noise, but that can be removed in PP.
did you turn long exposure noise reduction off?

if there's one thing i could change about my camera, it would be that. i wish i could be able to turn the bloody noise reduction off.

you'd think that waiting for a 4 minute exposure is gruelling enough, but waiting for another 4 minutes for your camera to somehow spit out the image so you can see if you did a botched job... ... well we've all been spoilt in the digital age.
 

#11
The focal length I used was 16mm.
.....So I used 6 5min exposures at f/5.6 and ISO 400. By stacking 6 frames only, the noise performance doesn't improve much at all...
Thanks.. Your picture turned out very clean and tidy. :thumbsup:
Did you have the noise reduction function on for each frame?
Erh..did you erase any "extra stars"?

if there's one thing i could change about my camera, it would be that. i wish i could be able to turn the bloody noise reduction off.

you'd think that waiting for a 4 minute exposure is gruelling enough, but waiting for another 4 minutes for your camera to somehow spit out the image so you can see if you did a botched job... ... well we've all been spoilt in the digital age.
I turned off the noise reduction, according to a "web-tutorial" but the pictures were noisy ( plenty of hot spots) even with 3 minutes exposure...may be I should try a lower ISO..
Actually the instruction was to obtain the first base frame with the NR on, then off the rest which are to be stacked..because NR consumes too much battery.
Won't the hot spots be accumulated with the overlay blending?

:bsmilie: yeah imagine lkkang shoots without seeing his products everytime...until hours/days later..
 

Jan 19, 2008
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#12
Thanks.. Your picture turned out very clean and tidy. :thumbsup:
Did you have the noise reduction function on for each frame?
Erh..did you erase any "extra stars"?
For stacking of many frames, turn off the NR, otherwise the camera will take a dark frame at the same exposure after each frame, you will end up with dashed trails instead of continuous ones. For random noise, the stacking will remove most of them if you stack enough.

For hot pixels, they cannot be removed by simple stacking. A dark frame subtracting is needed. Please refer to my post above. One advantage of taking short exposures is that you don't need a dark frame at long exposure.
 

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Ian

Senior Member
Feb 20, 2002
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Perth Australia
#13
did you turn long exposure noise reduction off?

if there's one thing i could change about my camera, it would be that. i wish i could be able to turn the bloody noise reduction off.

you'd think that waiting for a 4 minute exposure is gruelling enough, but waiting for another 4 minutes for your camera to somehow spit out the image so you can see if you did a botched job... ... well we've all been spoilt in the digital age.
Wait till it's a 180 minute exposure using hypersensitised film and a hand guided telescope, now that takes REAL SKILL ... sadly it's a dying art these days as there's few of us left who have the patience to do it.

On a general note:

Image stacking has been around in astrophotography years and years. I've been stacking B&W shots to produce a colour shot for years and image stacking sofware has been around for 15 years at least that I can recall. Registax was one of the first, then there's MaximDL (awsome but $400 USD or so for the full package) and many others.
 

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aspenx

New Member
Aug 10, 2008
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#14
Wait till it's a 180 minute exposure using hypersensitised film and a hand guided telescope, now that takes REAL SKILL ... sadly it's a dying art these days as there's few of us left who have the patience to do it.

On a general note:

Image stacking has been around in astrophotography years and years. I've been stacking B&W shots to produce a colour shot for years and image stacking sofware has been around for 15 years at least that I can recall. Registax was one of the first, then there's MaximDL (awsome but $400 USD or so for the full package) and many others.
Hand-guided telescope as in this kind of contraption?

As for hypersensitised film, do you mean films like Ilford SFX?

Anyways, a 40min exposure on a digital body sounds crazy. I don't know much but I would have worried about the camera overheating. No worries on a mechanical film camera though. Film reciprocity will allow much longer exposures without blowing it if you meter it right.
 

Jan 19, 2008
102
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#15
Wait till it's a 180 minute exposure using hypersensitised film and a hand guided telescope, now that takes REAL SKILL ... sadly it's a dying art these days as there's few of us left who have the patience to do it.

On a general note:

Image stacking has been around in astrophotography years and years. I've been stacking B&W shots to produce a colour shot for years and image stacking sofware has been around for 15 years at least that I can recall. Registax was one of the first, then there's MaximDL (awsome but $400 USD or so for the full package) and many others.
Are you the Ian on Singastro? If yes, long time no see man!
 

Jan 19, 2008
102
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#16
Hand-guided telescope as in this kind of contraption?

As for hypersensitised film, do you mean films like Ilford SFX?

Anyways, a 40min exposure on a digital body sounds crazy. I don't know much but I would have worried about the camera overheating. No worries on a mechanical film camera though. Film reciprocity will allow much longer exposures without blowing it if you meter it right.
Maybe ten or twenty years ago people used Hydrogen/Nitrogen hypersensitized films to capture those dim Hydrogen-emitting nebulae. One purpose of this is to get rid of the film reciprocity, which hinders capturing dim deep-sky objects.

I used to dream of doing astrophotography with that kind of films. But now things becomes much easier in digital age. However, if one seriously wants to capture the dim nebulae like those hpersensitized films, the IR block filter in front of the sensor needs to be removed to dig out the full potential of the sensor in capturing Hydrogen-alpha emission light.
 

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nuts

Senior Member
Jan 21, 2002
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#17
I usually use film for star trails. But one time my film SLR spoilt, so I use my EOS 50D. Exposed for 3609 secs and the NR kicked in. I had to wait 2 hrs to see my shot :)
At least it was reasonably clean. Haven't tried stacking, will do so one day.......... although it seems that stacking s/w is Windows only... :(



did you turn long exposure noise reduction off?

if there's one thing i could change about my camera, it would be that. i wish i could be able to turn the bloody noise reduction off.

you'd think that waiting for a 4 minute exposure is gruelling enough, but waiting for another 4 minutes for your camera to somehow spit out the image so you can see if you did a botched job... ... well we've all been spoilt in the digital age.
 

aspenx

New Member
Aug 10, 2008
1,350
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0
here
#19
Maybe ten or twenty years ago people used Hydrogen/Nitrogen hypersensitized films to capture those dim Hydrogen-emitting nebulae. One purpose of this is to get rid of the film reciprocity, which hinders capturing dim deep-sky objects.

I used to dream of doing astrophotography with that kind of films. But now things becomes much easier in digital age. However, if one seriously wants to capture the dim nebulae like those hpersensitized films, the IR block filter in front of the sensor needs to be removed to dig out the full potential of the sensor in capturing Hydrogen-alpha emission light.
I'm not open to removing the anti-IR filter on my digital body sadly.

How long will the exposures be say if I'm using the Ilford SFX film on a clear night at f/2.8?
 

Jan 19, 2008
102
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#20
I'm not open to removing the anti-IR filter on my digital body sadly.

How long will the exposures be say if I'm using the Ilford SFX film on a clear night at f/2.8?
Have never used the Ilford SFX film before, cannot make any comments on this...
 

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