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Old 01-01-2012, 07:24 AM
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Comet Lovejoy 1-1-12

Hi all, this morning comet Lovejoy has moved further away from the Milky Way to reveal the full extent of its tail and still visible to the naked eye. Many have asked how dark are my skies so I did a few tests this morning while exposing the comet. I can easily see the star within the Coalsack, counted 26 and up to 30 stars within Orion and the hardest was 3 stars within Corvus. I have not checked a star chart to see what magnitude they are as yet.

This image was taken with 50mm Canon F1.4 lens at F2, with 2 minute exposure using Canon 20Da at ISO 800. After taking this image and seeing I was not capturing the whole tail I replaced the 50mm lens with the 24mm F1.4L lens.

http://i638.photobucket.com/albums/u...s/6053b4cd.jpg

24mm lens at F3.2, 4 minute exposure

http://i638.photobucket.com/albums/u...s/5ef979a2.jpg

24mm lens at F3.2, 6 minute exposure

http://i638.photobucket.com/albums/u...s/64c83cf5.jpg
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  #2  
Old 01-01-2012, 07:30 AM
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You guys are blessed with a nice New Years Comet !!!!
Freddy
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Old 01-01-2012, 07:57 AM
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Nice work, Lester! The 24 f/1.4 is a ripper lens, isn't it?

I like Samir Kharusi's approach to measuring the sky fog because it's quick and easy - i.e. point the lens in a dark region near zenith and do a few test exposures to work out what exposure time would be needed for a middle-histogram sky fog peak at ISO 800 and f/4. He's also provided a translation scale between the exposure time and mag/sq arc sec for a Canon 1Ds.

http://www.pbase.com/samirkharusi/image/37608572
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Old 01-01-2012, 11:01 AM
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Great shots, Lester

I think we're going to see the full extent of the tail once the top half of it migrates over into the darker area next to the MW.
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Old 01-01-2012, 11:36 AM
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Thanks Freddy, Dave and Carl for your comments, as always.

Dave my lens is not the latest II version only the I model, and would like to know how much better the II is. This lens is okay, but I have heard the latest model is an improvement. Also I will look into that sky fog measuring, thanks.

All the best chaps for 2012.
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Old 01-01-2012, 12:18 PM
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You have done well Lester, lovely captures indeed.

Leon
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Old 01-01-2012, 12:21 PM
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Beautiful stuff Lester.

Steve
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Old 01-01-2012, 02:11 PM
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Great pics there.
Hope you dont mind, I used Iris gradient removal on your pic, what do you think?
Scott
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Click for full-size image (64c83cf5flat.jpg)
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Old 01-01-2012, 04:14 PM
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Aah, I only have the mark II version of the lens so all I can say is that it's quite fantastic (even compared to other L primes). My usually dilemma is trying to decide whether to open it up to f/1.4 for maximum light vacuuming (still remarkably sharp), or stop it down to f/2.8 - f/4 for better corners.
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Old 01-01-2012, 04:22 PM
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another beauty Lester. regards Ray
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Old 01-01-2012, 05:11 PM
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Thanks Leon, Steve, Scott, Dave and Ray for your comments, I appreciate them all.

Scott I like the gradient removal that program does = a real improvement. I will do a search and see how much that costs. I have tried Photoshop before but with mixed results.

Dave my 24mm L lens can produce seagulls wide open that I don't enjoy seeing. It would be good to be able to try before one buys these expensive lenses.
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Old 01-01-2012, 06:08 PM
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Nice new years comet capture Lester.

Cheers Kev.
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Old 01-01-2012, 06:32 PM
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Lester, Iris is free

Go here... http://astrosurf.com/buil/us/iris/iris.htm
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Old 01-01-2012, 06:45 PM
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Another beauty Lester, top stuff.

Cheers
Trevor
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Old 01-01-2012, 06:48 PM
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Thanks Kev, Carl and Trevor for your comments. I have just downloaded Iris, but the help menu doesn't work, so got no clue how to do a gradient removal. Is it easy?
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Old 01-01-2012, 06:53 PM
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Yeah, you have to download the help files separately, which is a bit strange.

Actually, if you look onsite, there's tutes that take you through how to do various things with Iris. I haven't had cause to use the gradient removal routine in any pics, so far, so you may have to ask Scott.

Should learn how it works
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Old 02-01-2012, 09:14 AM
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Howdy
In Iris, load the image you want to get rid of gradients from, then go to Processing, go down to Remove Gradient (polynomial fit), tick balance background colour then hit ok, normally the other default settings work well as they are.
Iris is free though has a steepich learning curve, theres all sorts of hidden functions, even I am still discovering things. The main help pages are here
http://astrosurf.com/buil/us/iris/iris.htm
under tutorial.
Hope that is of assistance
Cheers
Scott
Scott
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Old 02-01-2012, 09:34 AM
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Thanks for your help there Scott, I just tried and get message saying
"cannot save file" after I hit okay. Cannot procede from there.
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Old 02-01-2012, 10:34 AM
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hmm not sure why it did that. Normally when you click save, it will ask where you want to save it, and in what format eg jpeg.
Scott
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