Newbie Question: Aperture?

jrtf83 · 31st of December 2008 (Wed)

Hi guys,

It seems like the consensus is to shoot at higher ISO levels to achieve faster shutter speeds (less blur due to Earth's rotation).

What about aperture?

I've read some places that stars and things are "point" sources of light and so aperture does not affect them. This leads me to believe that stopping down might be the best thing to do, to hopefully mitigate some of my light pollution. Any truth to this theory?

As to my specific setup, I've just got my DSLR on my tripod with an infrared remote. So far i've just been shooting shortish (1-5 min) exposures and stitching 'em in CS3.

Thanks in advance for sharing all your wisdom,
Ross

Adrena1in · 31st of December 2008 (Wed)

As a relative beginner I tend to go for the lowest aperture possible when shooting anything but the moon. This is because I want to grab as much light as I can and as quickly as possible, to minimise any field rotation or drift error while tracking. So I usually shoot at ISO1600 as well.

I gather that on some lenses you can reduce certain aberrations by stopping down the aperture, but I don't know much about that myself.

Karl Johnston · 31st of December 2008 (Wed)

Lowest as possible, everything lowest as possible. Small numbers are = goooood.

Sorarse · 31st of December 2008 (Wed)

I too will use a wide open aperture to capture as much light as possible - including stars that would be too faint to see otherwise.

If light pollution gives you a funny coloured sky, that can be corrected in PS or similar.

PM01 · 1st of January 2009 (Thu)

Quote:

Originally Posted by jrtf83

Hi guys,

It seems like the consensus is to shoot at higher ISO levels to achieve faster shutter speeds (less blur due to Earth's rotation).

What about aperture?

I've read some places that stars and things are "point" sources of light and so aperture does not affect them. This leads me to believe that stopping down might be the best thing to do, to hopefully mitigate some of my light pollution. Any truth to this theory?

***Aperture affects plenty! Without it you will be capturing only the brighter stars. Getting the faint ones help too! When you stop down, you're effectively cutting down the amount of stars, nebulosity, etc that you can record. Simple Dawes Law.***

As to my specific setup, I've just got my DSLR on my tripod with an infrared remote. So far i've just been shooting shortish (1-5 min) exposures and stitching 'em in CS3.

***Which lens?***

Thanks in advance for sharing all your wisdom,
Ross

The larger the aperture, the more you can record. When you stop down, you're just using the "better" part of the lens. Now if it's a high end telescope, then stopping down won't help any as they are made to very critical specifications - ie - Astro Physics, takahashi, telescope engineering company, etc. With commercially made optics, it will.

fritzd · 1st of January 2009 (Thu)

A good lens is the tokina 11-16mm f2.8.. Very wide for a f2.8! A very good lens!

sam walker · 1st of January 2009 (Thu)

Love my depth of field as from f7 or 8 Also like focus and illumination of subject. Moving things are shot at 1/100-1/125 Shutter P ISO 100 Pretty safe. Crazy things like hummingbirds go 1/300+
Sam

jrtf83 · 1st of January 2009 (Thu)

I'm just getting started, so i'm still using the kit lenses.
Nikkor 18-55mm 3.5-5.6
and
Nikkor 55-200mm 4-5.6

was trying to get a decent shot of the venus/moon combo last night, but it didn't come out too well. I guess its time to upgrade my optics...

PM01 · 2nd of January 2009 (Fri)

Blurring?

Karl Johnston · 2nd of January 2009 (Fri)

Quote:

Originally Posted by fritzd

A good lens is the tokina 11-16mm f2.8.. Very wide for a f2.8! A very good lens!

here here

Jeff · 2nd of January 2009 (Fri)

Quote:

Originally Posted by sam walker

Love my depth of field as from f7 or 8 Also like focus and illumination of subject. Moving things are shot at 1/100-1/125 Shutter P ISO 100 Pretty safe. Crazy things like hummingbirds go 1/300+
Sam

Stars move a little slower than hummingbirds.

BestVisuals · 2nd of January 2009 (Fri)

Also realize that the smallest aperture isn't always the best, either. Around f/11 and smaller diffraction starts to noticeably effect the image quality. DOF expands but image quality actually degrades.

Adrena1in · 8th of January 2009 (Thu)

Quote:

Originally Posted by Jeff

Stars move a little slower than hummingbirds.

As a matter of fact, they move a heck of a lot faster. They're just so so far away it only *looks* like they're moving slowly!

31st of December 2008 (Wed)	#1
jrtf83 Junior Member Join Date: Dec 2008 Posts: 3	Newbie Question: Aperture? Hi guys, It seems like the consensus is to shoot at higher ISO levels to achieve faster shutter speeds (less blur due to Earth's rotation). What about aperture? I've read some places that stars and things are "point" sources of light and so aperture does not affect them. This leads me to believe that stopping down might be the best thing to do, to hopefully mitigate some of my light pollution. Any truth to this theory? As to my specific setup, I've just got my DSLR on my tripod with an infrared remote. So far i've just been shooting shortish (1-5 min) exposures and stitching 'em in CS3. Thanks in advance for sharing all your wisdom, Ross

31st of December 2008 (Wed)	#2
Adrena1in Senior Member Join Date: Aug 2007 Location: Winchester, Hampshire, UK. Posts: 1,703 IMAGE EDITING OK	Re: Newbie Question: Aperture? As a relative beginner I tend to go for the lowest aperture possible when shooting anything but the moon. This is because I want to grab as much light as I can and as quickly as possible, to minimise any field rotation or drift error while tracking. So I usually shoot at ISO1600 as well. I gather that on some lenses you can reduce certain aberrations by stopping down the aperture, but I don't know much about that myself. __________________ Canon EOS 450D, Sigma 18-200mm, Canon 50mm f/2.5 Macro, 2x TC, Revelation 12" f/5 Dobsonian, Mintron PD2285-EX webcam.

31st of December 2008 (Wed)	#3
Karl Johnston Rare exception that I didn't say anything stupid" Join Date: Jul 2008 Location: Canadian Arctic Posts: 9,020	Re: Newbie Question: Aperture? Lowest as possible, everything lowest as possible. Small numbers are = goooood. __________________ Adventure The Canadian Arctic With Me Canadian Features Editor of Let's Be Wild Adventure Magazine

31st of December 2008 (Wed)	#4
Sorarse Goldmember Join Date: Jan 2008 Location: Kent, UK Posts: 2,159 IMAGE EDITING OK	Re: Newbie Question: Aperture? I too will use a wide open aperture to capture as much light as possible - including stars that would be too faint to see otherwise. If light pollution gives you a funny coloured sky, that can be corrected in PS or similar. __________________ At the beginning of time there was absolutely nothing. And then it exploded! Terry Pratchett http://www.scarecrowimages.com Canon PowerShot G2

1st of January 2009 (Thu)	#6
fritzd Member Join Date: May 2008 Location: Currently in Ghent, Belgium but from Cebu City, Philippines Posts: 92	Re: Newbie Question: Aperture? A good lens is the tokina 11-16mm f2.8.. Very wide for a f2.8! A very good lens! __________________ FLICKR MULTIPLY

1st of January 2009 (Thu)	#7
sam walker Senior Member Join Date: Jan 2006 Location: cleveland ohio usa Posts: 1,899	Re: Newbie Question: Aperture? Love my depth of field as from f7 or 8 Also like focus and illumination of subject. Moving things are shot at 1/100-1/125 Shutter P ISO 100 Pretty safe. Crazy things like hummingbirds go 1/300+ Sam __________________ We'll rape the horses and ride off on the women rebel xs 18-55is,55-250is promaster2500 flash

1st of January 2009 (Thu)	#8
jrtf83 Junior Member Join Date: Dec 2008 Posts: 3	Re: Newbie Question: Aperture? I'm just getting started, so i'm still using the kit lenses. Nikkor 18-55mm 3.5-5.6 and Nikkor 55-200mm 4-5.6 was trying to get a decent shot of the venus/moon combo last night, but it didn't come out too well. I guess its time to upgrade my optics...

2nd of January 2009 (Fri)	#9
PM01 Senior Member Join Date: Dec 2007 Location: USA! Posts: 1,184	Re: Newbie Question: Aperture? Blurring?

2nd of January 2009 (Fri)	#12
BestVisuals Member Join Date: Apr 2007 Posts: 763	Re: Newbie Question: Aperture? Also realize that the smallest aperture isn't always the best, either. Around f/11 and smaller diffraction starts to noticeably effect the image quality. DOF expands but image quality actually degrades.

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