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Blurry stars. :(

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LRodney

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Hi All,

I was trying my hands on astro photography with my canon 40D and 50 f1.4 lens. All my pictures came up blurry and looks out of focus. Here are the settings that I have set.

1) Camera set on a tripod on a quiet road.
2) There's a 2 second timer delay
3) The mirror is set to lock up
4) No other known disturbance around.
5) Aperture set between f1.4 and 2.8 with ISO set to 1600
6) Focus set to infinity.

Is there anything I can do to improve on the photos? I've attached some of the photos below.

Thanks!















 
LRodney said:
I was trying my hands on astro photography with my canon 40D and 50 f1.4 lens. All my pictures came up blurry and look out of focus...

Is there anything I can do to improve on the photos? I've attached some of the photos below....
Click to expand...
Well, even with a 30sec exposure, you'll tend to get star "trails" due to the earth's rotation. That appears to be what you're seeing with the sample photos you've attached. You'll notice that each of the "stars" appears as a short "trail" [approximately upper left to lower right], which you're interpreting as being "out of focus".

If you get a motor-drive equatorial telescope mount [that will "track" the stars], you can pretty much eliminate that effect which would make your sky/star photos look "sharper". Also, with this kind of motorized "tracking", you'd be able to use longer exposures [at lower ISO and smaller aperture] which would also help the quality of the images.

Hope this helps.
 
Agree on the 30-second issue - that will likely introduce visible star movement even with a wider lens. Shorter exposure would likely help, and as those look a bit overexposed, you should be able to take shorter shutters and still get a properly exposed sky.

Also just to note: many lenses actually focus 'beyond' infinity - they actually can go just a hair out of focus if turned all the way to the infinity setting. Many lenses actually need to be dailed back just a smidge from maximum infinity focus to achieve proper infinity focus. Sounds strange I know - but you might have that situation with the lens you are using.

I would also strongly recommend using Live View mode and manual focus, if you haven't already. Live View will allow you to zoom in 7x or more and manually focus the lens. I believe if I remember correctly your camera has a live view mode...when shooting this type of scene, live view can be very helpful due to the zooming in ability when manually focusing.

--
Justin
galleries: http://www.pbase.com/zackiedawg
 
Probably due to Earth's rotation making star trails. Evidence is the final frame where the tree branches are sharp and the stars are blurred.

I'm not 100 percent sure your lens is sharp when focusing on infinity wide open, though--you might check this, too.
 
Infinity isn't always infinity. Manually focus on a bright star. Zoom in during playback, and check focus. This is how I do a quick focus when photographing thru my scope as well.

And this isn't star trail issues. Using a 50mm lens, you can go about 40+ seconds without much in the way of trailing. This is just a focus issue.
 
These shots appear out-of focus to me.

Here's a cropped section from one of my shots with an exposure time of 30 seconds:





Notice the stars are elongated into typical trails, caused by the rotation on the earth.

The samples posed do not look like this at all, the dominant effect seems to be the lens not correctly focussed at infinity.

Regards,
Peter
 
Agreed. It's a focus issue. Trailing isn't evident in the shots all that much. Depending upon where you're pointing in the sky, you can go from about 15 seconds to a minute with a 50mm lens.
 
Not too bad. You must have really dark skies. If you want pinpoint stars, then you'll have to reduce exposure to say 20 sec at f/3.5 or smaller at ISO 800+

If you really are serious, get a tracking mount, then you can expose 5 min or more.

Ciao....BC
 


try using a wider angle lens this photo was shot with a 20mm 2.8 lens iso800 30sec.



this shot is with a 50mm 1.4 800 at 10 sec
I find that the stars look sharper with the 20mm because the stars look smaller

--
Later
Rick
 
suggest you look into image stacking. this is when you take multiple images of of the same sky scene then let software stack the images. the software takes the info from each image and adds it to the next. images of the planets can be done this way. also night scenes.

see-
http://www.tawbaware.com/imgstack.htm
http://www.astrostack.com/
http://www.astronomie.be/registax/

also-
http://www.astroviewer.com/news.html
http://www.astropix.com/

there is also users who use a camcorder and shoot 200 or so frames of the sky and stack all 200.
 
The last shot yells "mis-focus" to me actually. The branches are quite sharp, while the stars are not. Star-trails would be easy to spot, as that means a blur in one direction, rather than all around. Any motion blur from an unsteady tripod or something similar would show on the branches as well.

So after excluding subject-motion and camera-motion, the only remaining cause of unsharpness, focus-problem, remains. As some have mentioned, the far end of the focussing ring on most lenses is actually past infinity. And with apertures of f/1.4 to f/2.8 you won't get much depth of field. The hyperfocal distance of a 50mm lens at f/1.4 is around 100 meter. So if you focus on something at that distance, you should get the stars in focus. At f/2.8 it's 50 meters.
 
GaryDeM said:
suggest you look into image stacking. this is when you take multiple images of of the same sky scene then let software stack the images. the software takes the info from each image and adds it to the next. images of the planets can be done this way. also night scenes.

see-
http://www.tawbaware.com/imgstack.htm
http://www.astrostack.com/
http://www.astronomie.be/registax/

also-
http://www.astroviewer.com/news.html
http://www.astropix.com/

there is also users who use a camcorder and shoot 200 or so frames of the sky and stack all 200.
Click to expand...
Sorry....but what does this have to do with fixing his problem? Stacking will not solve a focus issue. It only helps increase SNR, and makes it easier to deal with multiple flat fields, dark frames, and extending exposure time.
 
GideonW said:
The last shot yells "mis-focus" to me actually. The branches are quite sharp, while the stars are not. Star-trails would be easy to spot, as that means a blur in one direction, rather than all around. Any motion blur from an unsteady tripod or something similar would show on the branches as well.

So after excluding subject-motion and camera-motion, the only remaining cause of unsharpness, focus-problem, remains. As some have mentioned, the far end of the focussing ring on most lenses is actually past infinity. And with apertures of f/1.4 to f/2.8 you won't get much depth of field. The hyperfocal distance of a 50mm lens at f/1.4 is around 100 meter. So if you focus on something at that distance, you should get the stars in focus. At f/2.8 it's 50 meters.
Click to expand...
The hyperfocal distance gives a minimum distance for the chosen substitute subject. By substitute, I mean, instead of attempting to focus on the stars, choose some alternative. My point is, it should be no closer than the figures quoted, but can be further away. Examples would be a well-lit building, or simply a street light, somewhere at a far distance.

Then either auto or manually focus on that subject, and switch to manual-focus mode so that the lens will not refocus when aimed at the actual subject to take the sky photo.

Regards,
Peter
 
I don't shoot any star trails, but I do a lot of moon shots, and from my experience, any shutter speed longer than 2 seconds will give motion blur.

Lunar eclipse 8-28-2007 (Panasonic Lumix FZ50 on tripod, manual focus & exposure):
  • First shot: f/5.6, 1/400th sec, ISO 100

  • Second shot: f/5.6, 1/400th sec, ISO 100

  • Third shot: f:5.6, 1/125th sec, , ISO 100

  • Fourth shot: f/5.6, 1.6 sec, ISO 100

  • Fifth shot: f/5.6. 4 seconds, ISO 100


--
J. D.
Colorado
 
Using a 50mm lens, depending upon how far from the pole you're exposing, expsosueres can run between 15 and 45 seconds with virtually no motion blur. Lunar photography (far more difficult) needs reduced exposure times because of increased focal length required.
 
sorry. it will fix his problem. since with image stacking you can use 1/2 the exposure time. this ordinarlily would give too little image info, but since the images will be stacked the info is additive. and it cuts the apparent movement in half. so instead of using a 30sec exposure, you use a 15sec exposure then stack as many as you wish. the say 6-9 images all with too little exposure at 15sec are now stacked the total image info is now available. also note the jerry lodriguss website. this has a tremendous info base on not only taking the shots buy pping with photoshop later to bring out the very best image. jerry's before and after images are very impressive.
 
GaryDeM said:
sorry. it will fix his problem. since with image stacking you can use 1/2 the exposure time. this ordinarlily would give too little image info, but since the images will be stacked the info is additive. and it cuts the apparent movement in half. so instead of using a 30sec exposure, you use a 15sec exposure then stack as many as you wish. the say 6-9 images all with too little exposure at 15sec are now stacked the total image info is now available. also note the jerry lodriguss website. this has a tremendous info base on not only taking the shots buy pping with photoshop later to bring out the very best image. jerry's before and after images are very impressive.
Click to expand...
Stacking will NOT fix a focus problem. It will fix an issue with poor tracking or trailing on an unguided mount. Stacking multiple blurry, out of focus images will not produce a sharper image.

I've done enough of this type of photography to know the difference between guiding errors and OOF images....and these images are OOF.

If I'm photographing thru my Celestron CGE1400, if I stack a bunch of OOF images...they don't get sharper. Sorry!
 
this is the image #2. actually therew isn't much wrong with it. the image blur was off by 4 pixels and that was fixed in focus magic. and then some levels work.

 
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