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72-minute Bulb exposure problem

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Leakeem
216 posts
72
Message posted at 11/13/2012, 00:39:44 AM by Leakeem
Last week, I did a 72 minute bulb exposure of the night sky. I was trying to photograph the stars. I was on Manual mode, f/22 and ISO 100. My Noise reduction settings were set to not do any noise reduction on long time exposures. After the exposure I noticed that my fully charged battery is almost empty and the camera is recording the image for a long time. It took about 20+ minutes before my battery ran out and my camera shut down.

Does anyone have experience with very long bulb exposures? Does it really take that long to record? or something is wrong with my camera? I'm guessing wrong settings but what could have it been?
Canon EOS 550D, Nikon 50mm f/1.4, Nikon P100, ASUS K24Jl

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Bogdan
360 posts
70
Message posted at 11/13/2012, 02:31:26 AM by Bogdan
72 minutes is way too long. Use shorter (in astrophotography 3 or 5min exposures are usually employed) and then stack them in post-processing... Newer cameras can record the image faster after the exposure, but it still takes some time.

Bogdan

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Igordabari
3702 posts
62
Message posted at 11/13/2012, 03:57:01 AM by Igordabari
My maximum exposure was about 45 minutes with noise supression switched ON, so practically it was 90 min exposure. The battery was not completely discharged, though it lost more than half of its charge. Maybe much more than half - I do not remember.

Here in my DT porfolio there are two shots which were done wiyj 31 min and 22 min exposures, correspondingly:

   Star trails space   

   Seliger lake: night stars   

By the way, what was a reason to use f/22? I guess that nothing except for the moon could be visible at such a low aperture. Or I am wrong?

I, me, myself + cameras: Canon 450d (for astrophoto...

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Nospmisk
364 posts
61
Message posted at 11/13/2012, 08:29:57 AM by Nospmisk
My longest exposure is no more than 10 minutes. After that sensor damage can occur from the heat.
Rack em and stack em.

Here is a 10 minute:
   Natural Bridge in Santa Cruz   
© Kyle Simpson | Dreamstime.com
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Leakeem
216 posts
72
Message posted at 11/13/2012, 09:11:48 AM by Leakeem

Originally posted by Bogdan:
Quoted Message: 72 minutes is way too long. Use shorter (in astrophotography 3 or 5min exposures are usually employed) and then stack them in post-processing... Newer cameras can record the image faster after the exposure, but it still takes some time. Bogdan


That was my 2nd try with bulb LT exposure. my first was 15 minutes but I was not happy with the "star trails" so I thought: "make it longer." I didn't know those long trails were stacked in photoshop. thanks!
Canon EOS 550D, Nikon 50mm f/1.4, Nikon P100, ASUS K24Jl

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Leakeem
216 posts
72
Message posted at 11/13/2012, 09:17:53 AM by Leakeem

Originally posted by Igordabari:
Quoted Message:  By the way, what was a reason to use f/22? I guess that nothing except for the moon could be visible at such a low aperture. Or I am wrong?


I was "guessing" that time. I was itching to try another bulb exposure of the stars so even if the sky is glowing because of the city lights and the smog I still tried to go with the shot. Besides, there's no harm in trying. Stars were partly visible but the sky's glow is also evident. so I thought: small aperture + longer exposure time might give me a nice nightscape with star trails as background. I never found out if the guess was right.
Canon EOS 550D, Nikon 50mm f/1.4, Nikon P100, ASUS K24Jl

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Leakeem
216 posts
72
Message posted at 11/13/2012, 09:22:58 AM by Leakeem

Originally posted by Nospmisk:
Quoted Message: My longest exposure is no more than 10 minutes. After that sensor damage can occur from the heat.Rack em and stack em.


I heard (and seen) of noise due to heat around that times but this is the first time I heard of damage due to heat. I guess I need to be more careful next time.
Canon EOS 550D, Nikon 50mm f/1.4, Nikon P100, ASUS K24Jl

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Nospmisk
364 posts
61
Message posted at 11/13/2012, 09:25:42 AM by Nospmisk

Originally posted by Leakeem:
Quoted Message: I heard (and seen) of noise due to heat around that times but this is the first time I heard of damage due to heat. I guess I need to be more careful next time.
It causes sensor hot spots (single pixel destruction).
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Igordabari
3702 posts
62
Message posted at 11/13/2012, 09:34:27 AM by Igordabari

Originally posted by Nospmisk:
Quoted Message: It causes sensor hot spots (single pixel destruction).


"Hot pixels" are easily eliminated when shooting (by applying noise suppression) and the rest of them can be removed in post-processing. Antway, I never had problems with hot pixels even when exposure was as long as 30 minutes. I am quite sure that even 60-min expositions are possible given that sky is dark enough.
I, me, myself + cameras: Canon 450d (for astrophoto...

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Igordabari
3702 posts
62
Message posted at 11/13/2012, 09:42:49 AM by Igordabari

Originally posted by Leakeem:
Quoted Message: Stars were partly visible but the sky`s glow is also evident. so I thought: small aperture + longer exposure time might give me a nice nightscape with star trails as background.


If sky is dirty of city-light one can try what Bogdan said: multiple relatively small exposures + stacking. But on my experience it is impossible to get nice picture with star trails near city, one shoud go to countryside.

In any case I think that f/22 is not a good solution. For most lenses the good compromise is about f/5...f/6 which allows to get light enough (on the one hand) and avoid chromatic abberations (on the other hand).

Good luck for sky shooting and I would be grateful to you if you let me know the ID of your first results. Thanks in advance!
I, me, myself + cameras: Canon 450d (for astrophoto...

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