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Old 21-06-2008, 02:21 PM
TrevorW
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DSO Newbie

How many images of what exposures are required to produce a reasonable image of a star field resembling what you may see through the EP or in magazines and on the image pages of this forum.

Are these images acheivable using a DSLR with standard lenses or is it preferable to use the DSLR attached to a scope at prime focus.

Images I've taken so far using the DSLR with lens seem just like lifeless uninspriing dots on a dark background.

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Old 21-06-2008, 05:18 PM
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Matty P (Matt)
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Hi Trevor,

It really depends on what you want to image and how you want to do it.

If you want to do widefield images, a DSLR with a standard lens on a tracking mount will allow you to get some great shots of the Milky Way.

Prime focus photography with a scope will allow you to image Galaxies and Nebulas because you are using a longer focal length.

As for the exposure time, anywhere between 4min-8min is probably the ideal exposure time for long expsoure photography with a DSLR. You will want to capture as many exposures as possible in an imaging session to get the best results.

Pretty basic but I hope it helps.
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Old 21-06-2008, 06:09 PM
TrevorW
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Matty, 4-8 minute exposures may be problematic with a motor driven EQ5 mount. Looks like that EQ6 with autoguider may be a necessity for those long exposure times. Also is it preferable to take the images in RAW mode.

Thanks
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Old 21-06-2008, 09:18 PM
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Tandum (Robin)
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RAW mode is prefered as once you have a dozen or so images, you combine them with dark, flat and bias images in software to reduce the noise, and basically this is like doing maths on a large spreadsheet file except the numbers in each box are huge with lots of decimal points. RAW files from my 450D are 14bit files making the numbers possibly enormous.

My scope is out back now imaging M83 again, this time with my new light pollution filter. Just done 4 x 10minutes @ 800 iso but I can see from the images that my mount and guiding isn't up to 10 minute exposures so it's now running at 5 minutes @ iso 800. After I get a stack of those I'll try 5 minutes @ iso 1600 and see what they look like.
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Old 22-06-2008, 04:22 AM
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Tandum (Robin)
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Update ... they where all crap ... low ISO is best to beat the noise. I'll try again next week when that moon isn't so bad...
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Old 22-06-2008, 11:08 AM
TrevorW
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Quote:
Originally Posted by Tandum View Post
Update ... they where all crap ... low ISO is best to beat the noise. I'll try again next week when that moon isn't so bad...
Yeah know what you mean trying to get a half decent shot of the moon and Jupiter are hard when the moons full and it's not halfway through the night. Clear and cold hear last night but a lot of turbulence around 8:30-9:00pm tried a couple of sessions both with the DSLR and Afocal but crap as well.

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