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Old 29-09-2008, 11:59 AM
Ian Robinson
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Not necessarily, you'd be surprised the difference it makes to the final image.
Try it first before forming an opinion, temp differentials in darks causes horrible black dots everywhere in the image.
The closer your darks are in temp to your lights the better.
Interesting .... so from experience .... how many "lights" can you get away between "darks" and still get good noiseless stacked images post processing using a 40D ?

How does this change with exposure length (of each "light" / "dark") ? with effective speed (ISO) ?

I know I have a lot to learn about this digital imaging "black witchcraft". Film imaging was heaps simpler .... you took the battery out , aimed , focused , set the camera to manual , and pressed the T button (if you had one) or the pressed the B button and locked the cable to down until you were ready end the exposure , at the end of the session or roll of film , you took the roll out and gave it to photolab to process and print .... nice !!!

Last edited by Ian Robinson; 29-09-2008 at 12:09 PM.
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  #22  
Old 29-09-2008, 12:35 PM
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RB (Andrew)
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Originally Posted by Ian Robinson View Post
Interesting .... so from experience .... how many "lights" can you get away between "darks" and still get good noiseless stacked images post processing using 40D ?
Depends on how much time you are spending on an object per night and the length of exposure.
If you are doing say 5 or 10 min subs then you can take a dark every second or third shot.
Temps can change within that time frame especially in the warmer months and regions.

Quote:
How does this change with exposure length (of each "light" / "dark") ? with effective speed (ISO) ?
Obviously if you're only doing shorter exposures say between 30 sec to 120 sec you can fit more lights in between darks.

ISO?? same deal.

Quote:
I know I have a lot to learn about this digital imaging "black witchcraft". Film imaging was heaps simpler .... you took the battery out , aimed , focused , set the camera to manual , and pressed the T button (if you had one) or the pressed the B button and locked the cable to down until you were ready end the exposure , at the end of the session or roll of film , you took the roll out and gave it to photolab to process and print .... nice !!!
People also use to ride around on horses, nice and simple hah?

The astute film astro imager would develop their own film, even make colour prints, which was more complicated.
They didn't trust the lab to get it right, most of the time you had to remind them not to cut the negs.

And lets not forget that you needed to keep very good records of your procedures when exposing so you could analyze what when wrong on Saturday night when you get your photos back from the lab the following Wednesday. (no instant feedback on what you're doing wrong).
Nice and simple huh?

Digital is similar, the astute astro imager will learn from other's experience and apply the techniques to their work and get results.

The other option with DSLR's is to pop the battery in, focus, put it in bulb mode, release the shutter and save the image off the card in jpg ready for the web .....nice ??

My point is to get results you need to put the effort in to learn first from others and from your own mistakes and experience, in anything you do in life.
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  #23  
Old 30-09-2008, 02:01 PM
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g__day (Matthew)
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I suggest a USB -> Camera Bulb serial connector (DSUB unit) from ShoeString Astronomy plus Craig Stark's DSLR Shutter (freeware) or Nebulosity to run your Canon Camera.
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