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PostPosted: Fri Sep 14, 2007 4:43 pm 
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Hi folks,

I am still getting ready to try my 40D out at night for the first time but today I came across a very detailed article at Christian Buil's web-site. It describes the pros and cons of using the 40D in astrophotography, including a nice illustration of using the PC to control everything on the camera including focussing.

Bob.

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OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Fri Sep 14, 2007 10:27 pm 
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Great article Bob - I was tempted to include more detail on the subject in my main review but thought I might alienate some people!

But for newcomers to astrophotography, one of the biggest challenges is focusing, so being able to magnify a portion in Live View AND electronically focus the lens using PC software is the holy grail for astro-photographers!

As I mentioned in my review though, unless you have a super bright lens, you'll only see the very brightest stars on the screen- but that's still enough to get your focus.

Another neat feature of the 40D's software is being able to program-in a Bulb exposure using your PC, eliminating the need for a cable release and stop watch - so long as you have a computer within the USB cable's length of the camera of course!

Gordon


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PostPosted: Fri Sep 14, 2007 10:31 pm 
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Gordon wrote:
of the biggest challenges is focusing

Please enlighten me: Since when is focussing to infinity a challenge?

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PostPosted: Fri Sep 14, 2007 10:49 pm 
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Thomas, it's too dark for a camera to auto focus on stars, so you have to do it manually. Trouble is, infinity isn't actually at the end of a lens focusing range! As you know most focusing rings can be turned a bit beyond infinity (hang on, didn't Buzz Lightyear say that?), and the actual infinity marking on the lens can't be relied upon. So I'm afraid it all has to be done visually through the optical v/f.

And remember the camera could also be mounted on a telescope which doesn't have an infinity setting...

This is why a magnified view is such a boon for astro-photographers...

Gordon


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PostPosted: Fri Sep 14, 2007 10:54 pm 
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tombomba2 wrote:
Gordon wrote:
of the biggest challenges is focusing

Please enlighten me: Since when is focussing to infinity a challenge?

I hope you don't mind me butting in.

For me, the problem is that my lenses all focus "beyond" infinity when you turn the focus ring all the way around. That's actually a good thing as it allows some leeway for filters placed in the optical path after the lens.

Stars are incredibly good at showing up the least bit of misfocussing and are generally too dim to allow normal manual focussing anyway. Hence the usual series of test exposures while tweaking the focus.

The Live View plus notebook display facility should solve all this if you can find a star bright enough for the lens in use as you can not only focus in real time and in comfort from the computer but you are actually focussing using the sensor itself.

Give the old way a try one evening and take some star trails.

Bob.

P.S. SNAP - simultaneous posting!

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OM-D E-M1 + ED 12-40mm f/2.8, H-F007014E, M.ZUIKO DIGITAL 45mm 1:1.8, M.ZUIKO DIGITAL ED 75mm 1:1.8, L-RS014150E.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Thu Oct 04, 2007 11:41 am 
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I think this would interest you a fair bit Bob.

Live View 40D Autofocus

DavidL

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PostPosted: Thu Oct 04, 2007 8:58 pm 
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Hi David, hope you don't mind, I modified your link to go straight to the supplier's page. I've actually been in touch with the developer Chris Breeze, and hope to test this software next time I get the 40D in.

I asked Chris to explain the differences between his program and the supplied EOS utility:

"DSLR Remote Pro offers an number of enhancements over EOS Utility in live view. In live view you can focus using the left and right cursor keys or the mouse wheel - both methos work better than having to take you eye off the image to find the near/far focus buttons. It also has an autofocus option that works by adjusting the focus and comparing the images before and after to assess whether the focus is better or worse and then loops round again until optimum focus is achieved. This can take several seconds and isn't foolproof. The focusing is an open loop control system i.e. there is no feedback for the lens focal length, and this works better with some lenses than others. I find it generally works well with Canon USM lenses and less well with my Sigma and Tamron lenses.
Live view also has an onion skinning option which is useful for stop motion animation and for lining up multi-shot panoramas.

In addition to live view DSLR Remote Pro has an auto-bracket option which can take up to 15 shots keeping the aperture the same and varying the shutter speed making it ideal for HDR photography.

I also have a multi-camera version. It was used by a Hollywood special effects company to control 120 Canon EOS 30D cameras using 5 laptops."

Sounds good!

Gordon


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PostPosted: Fri Oct 05, 2007 1:45 am 
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Thanks Gordon for the news from the horses' mouth.
Sounds very good !
I'll be waiting for your review on it - soon I hope.
May just tip the scale for me and change me to a "Canonite"

DavidL

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