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  #1  
Old 20-08-2008, 02:50 PM
Dennis
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M8, M20, M21 and Comet Lulin - Canon 400mm F5.6 test

Hello,

Last night (Tue 19th August) I tried some long exposure, wide field imaging with the Canon 40D and Canon 400mm F5.6, despite a nearby almost full Moon. The lens was set to F5.6 (wide open) and no Flat Fields were taken. I used “In Camera Noise Reduction” after seeing the results of Bert’s tests with his 5D. The location was suburban Brisbane, some 7kms from the CBD.

I selected M8, M20, M21 and Comet Lulin as the target for the lens test. The final shot was a combination of 3 x 3 min and 5 x 2 min exposures, each captured with ICNR. Apart from a small tweak of levels, no processing has been done.

Here is an inventory:
  • Raw Frames 3888x2592 aligned and combined in ImagesPlus and saved as full sized TIF.
  • TIF opened in CS3, down sampled and saved as a 1600x1062 jpg.
  • Sub-Frames cropped from full size TIF and saved as 1280x960 JPGs in CS3.
Needless to say, I was simply blown away with the performance of this lens, wide open and will certainly be looking forward to exercising its potential at a dark sky site. I particularly like the star colours! Oh the unbridled joy of wide field imaging!

Thanks to Clive and Roger for their help in teaching me how to generate the constrained crops for this exercise.

Warning: Large file sizes and 1600x1062 images.

Cheers

Dennis
Attached Thumbnails
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Click for full-size image (Full-frame-1600-Overlays-Text.jpg)
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Click for full-size image (Comet-Lunlin.jpg)
109.6 KB125 views
Click for full-size image (M20-M21.jpg)
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Click for full-size image (Centre-crop.jpg)
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Click for full-size image (M8.jpg)
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  #2  
Old 20-08-2008, 04:04 PM
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Jeffkop (Jeff)
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They look great Dennis, I was thinking of getting a 18 to 300mm for my 40D. By the look of it 400mm is better !!!
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  #3  
Old 20-08-2008, 05:15 PM
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Very nice indeed Dennis.. The M20/M8 image is a real stunner, and with minimal processing its actually very very pleasing..

The 400 5.6 is a great little wide field APO hey!

MORE! I demand MORE!
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Old 20-08-2008, 05:33 PM
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Matty P (Matt)
Star Struck

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Great work Dennis, looks like a great widefield lens.

The one thing that really stands out is the star colours. The colours are very vivid and range from deep reds to blues. Very nice indeed. I love it.

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  #5  
Old 20-08-2008, 06:22 PM
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strongmanmike (Michael)
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You are quite right Denis, that does appear to be a ripper of a lens What lens is it exactly ie if I wanted to buy one for a Canon DSLR what would I ask for to ensure I got the same one?

Mike
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  #6  
Old 20-08-2008, 06:58 PM
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Striker (Tony)
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Nice work Dennis.

It always amazes me what is capable frpm the city suburbs.

Mike here it is cost approx $1500.00 http://www.canon.com.au/products/cam...mmF56lUsm.aspx
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  #7  
Old 20-08-2008, 07:09 PM
Dennis
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Thanks guys, I think my prime focus, long focal length imaging through an F12 optical tube are over! It was so sweet to not have star trailing and guide star issues with the 400mm F5.6.

I’m not sure if the “central hot spot” is a hot spot/vignetting artefact or simply the Sagittarius star clouds? Next time, I’ll take some Flats to see what results I get.

Mike – the 400mm F5.6 cost me just over $1400 from Discount Digital Photographics and it pairs up nicely with the Canon 40D. Remote Live View running on the notebook was an essential aid for manual focusing, absolutely indispensible IMHO.

Cheers

Dennis
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Old 20-08-2008, 08:16 PM
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You /KNOW/ you want a 600 F/4L now don't you..
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Old 20-08-2008, 09:22 PM
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strongmanmike (Michael)
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Thanks Tony and Dennis

It looks to be a nice lens but I think F5.6 is just a bit slow, any recomendations on something faster? I guess more expensive too but a 300mm F2.8 (or faster) would be good.

Mike
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Old 20-08-2008, 10:17 PM
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mmm my 300 2.8 is yet to be tested for astro work, have not managed to find a way to securely mount it yet... (its HEAVY!)

The 300 2.8 with a 1.4TC gives a nice 420 at F/3.5 Thats the winner right there...
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Old 20-08-2008, 10:41 PM
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Chippy (Nick)
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Hi Dennis,

Fantastic images from Brissy!!! What was your mount, etc?
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  #12  
Old 21-08-2008, 07:45 AM
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RB (Andrew)
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Quote:
Originally Posted by Dennis View Post
Needless to say, I was simply blown away with the performance of this lens, wide open and will certainly be looking forward to exercising its potential at a dark sky site. I particularly like the star colours! Oh the unbridled joy of wide field imaging!
Cheers

Dennis
I don't blame you Dennis, excellent results, love the star colours and wide open there's no CA evident.
Very nice lens.

Quote:
Originally Posted by Jeffkop View Post
They look great Dennis, I was thinking of getting a 18 to 300mm for my 40D. By the look of it 400mm is better !!!
Which 18-300mm were you thinking of?

Quote:
Originally Posted by strongmanmike View Post
It looks to be a nice lens but I think F5.6 is just a bit slow, any recomendations on something faster? I guess more expensive too but a 300mm F2.8 (or faster) would be good.

Mike
Yes a 300mm f2.8 is expensive but it is stunning.
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  #13  
Old 21-08-2008, 07:55 AM
Dennis
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If you search on 300mm F2.8, you should see some of the superb results from Scott, Bert and Leon who from memory, have posted several wide open images from this lens.

Cheers

Dennis
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  #14  
Old 21-08-2008, 11:29 AM
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Lovely widefields Dennis, That 400mm lens certainly sounds like a beauty.

Cheers
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  #15  
Old 21-08-2008, 02:18 PM
Dennis
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Thanks Ric – it was an absolute pleasure to be imaging at only 400mm instead of the usual 1700+mm!

Cheers

Dennis
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  #16  
Old 21-08-2008, 03:47 PM
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Hi Dennis!
They're awesome images!
Just one thing i'd like to add is, this demonstrates that not only should one be looking out for the nebulae subject but also whats going on around it! Notice the movements of C/2007 N3 Lulin! Even though stacked images boost S-N Ratio's they also have the knack of bringing out any potential discoveries!
I'd like to see if anyone out there has compared an image to an older one of the same region in case of objects like comets and novae/supernovae etc.....
While ever you are photographing the stars the chances for discovery are much higher if you take notice of any changes! Of course we wouldn't want to flood the CBAT of false alarms (they HATE that!) but anything in suspicion should be backed up by other observers....a forum such as this and others is a very reliable and up-to-date tool that shouldn't be overlooked!
Great stuff Dennis!
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  #17  
Old 23-08-2008, 08:17 AM
jase (Jason)
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Excellent work Dennis. I like how you've display a map of the individual frames to put targets into perspective. The lens appears to be a real performer. Look forward to seeing more. Well done.
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Old 23-08-2008, 12:19 PM
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Very nice Dennis. Your lens is a real performer yielding good star images.
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  #19  
Old 23-08-2008, 12:52 PM
Dennis
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Thanks for the nice comments guys. Just to make sure there is no confusion, there is only a single image here of that entire region. The 5 off crops at 1280x960 are full resolution crops from the original single frame, just to show how the lens performs.

Cheers

Dennis
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  #20  
Old 24-08-2008, 08:32 AM
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multiweb (Marc)
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great widefields - it puts all those targets into perspective and stars are consistantly round all over. real cool
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