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  #21  
Old 09-10-2007, 08:19 PM
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RB (Andrew)
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Quote:
Originally Posted by Ingo View Post
Canon Optics are better Takahashi uses Canon's Fluorite Elements
Used 400 F2.8 IS's are very much under the new price, and can be sold for the same price again when you bought it used.
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Originally Posted by Benny L View Post
I have the 400 f2.8L IS USM, bought it new for 12K you can pick up ex-press ones for 5-6 K or you can hire from some places for 150-200 bucks a day
Firstly, I think this thread's wondered off topic because the OP (Andrew) specifically stated a budget of around $1500 not $5-6K and is looking at a relatively widefield lens.

My reply to Ingo was meant more as a subtle hint to this fact than anything else but since the point is brought up - here is my point of view.

There are specific pieces of equipment for specific jobs, in this thread we are solely talking about astro imaging and since we're putting cost to one side let's compare the two glasses and let's say both the Canon 400mm F/2.8 IS and FSQ 106 can be bought for around $6K (AU).
Which would be better suited for astro imaging ???

The FSQ 106 has a 4" Rotatable Focuser, has an imaging circle of 88mm, comes with a 10 to 1 focuser and is an astrograph.

The Canon 400mm IS f/2.8 L is a super sharp wildlife/action/sports lens with one Fluorite element that is designed for these purposes. The fact that it has IS means nothing since IS serves no purpose for astro imaging and since astro imaging places a huge demand on the optics we run the risk of CA showing up due to the IS mechanism not always being perfectly placed in the park position when turned off.
This of course doesn't really show up in terrestrial shots but in astro imaging it has an effect.

Now as you know I'm a big fan of the Canon super primes but if I was to specifically buy glass for astro imaging, my choice would be to get the right tool for the job.
If I wanted to use it for daytime shots as well then I'd consider the Canon lens only because I can use it for other purposes.

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  #22  
Old 09-10-2007, 08:33 PM
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Originally Posted by andrew View Post
I'm definitely looking at wide-field. As for budget.....less than $1500 is preferable.. The main incentive is to take a step up from the standard lens kit that came with the camera, as it doesn't seem appropriate for astrophotography.
Andrew I'd seriously be considering any of the following lenses depending on your FOV preference.
These prices are aprox only.

Canon 135mm f/2 L ($1599)
Canon 200mm f/2.8 L ($995)
Canon 17-40mm L f/4 ($955)
Canon 10-22mm EF-S ($899)
Sigma 17-70mm f/2.8 ($515)
Canon 50mm f/1.4 ($459)
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  #23  
Old 10-10-2007, 12:02 AM
mymoon (Aziz)
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this dude did a comparison between a Canon 600mm f4 and a TV140

http://www.samirkharusi.net/televue_canon.html

and using his technique here

http://www.pbase.com/samirkharusi/beginners

a picture of the Milky way using Canon 20D and a 50mm f1.4 from my lense bin (although he suggested a 50mm f1.8) single exposure

http://www.pbase.com/aziz/image/79623788.

AF on jupiter and recompose. Are the M's correctly labelled?

cheers
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  #24  
Old 10-10-2007, 01:19 PM
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There are also the cheaper plastic case lens types. The Canon 50mm f/1.8 is only $150 at teds camera house. How would the images from this lens compare with the Canon 50mm f/1.4 ($459) ??? Im only planning the occassional night shot with my Canon400D
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  #25  
Old 10-10-2007, 02:18 PM
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Quote:
Originally Posted by Domol View Post
There are also the cheaper plastic case lens types. The Canon 50mm f/1.8 is only $150 at teds camera house. How would the images from this lens compare with the Canon 50mm f/1.4 ($459) ??? Im only planning the occassional night shot with my Canon400D
I have one 135mm Hanimex lens (plastic case) and I found it awful (completely out of centre).

In the course of my testing I found that Pentacon 50mm f1.8 lens (Praktica, ~$50 on ebay) produces quite decent star images, provided it is stopped down to f4 - f5.6. The same applies to majority of Zenit lenses as well.
Generally, prime lenses perform better than zoom's... Of course, if they are in the same price category.
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  #26  
Old 10-10-2007, 05:02 PM
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The 50mm f/1.8 does a pretty respectable job stopped down to around f/3 or slowere. For a very inexpensive lens it does a good job. It's not an L, but then you aren't paying for it either.

LMC
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  #27  
Old 10-10-2007, 08:47 PM
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paul,
you siad that you need to "stopped down to around f/3", so what happens if you use the full 1.8 apature? Fuzzy?
Also what's an "L"............that's right i'm a newbie!
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  #28  
Old 10-10-2007, 09:30 PM
Benny L (Ben)
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Quote:
Originally Posted by Domol View Post
paul,
you siad that you need to "stopped down to around f/3", so what happens if you use the full 1.8 apature? Fuzzy?
Also what's an "L"............that's right i'm a newbie!
Using a lens "wide open" will make the imperfections/errors of the glass in the lens more obvious... for me and my work i always stay between 1 stop from fully open and 1 stop from fully stopped down.

so for a 50mm f1.4 i would shoot between f2 and f11, as a general rule the "mid-point" of a lens i.e f5.6-f11 gives the lenses sharpest result. this is because the lens is using the centre most bits of glass in the lens which does not have as much curvature as the outer parts of a lens would. aspheric lenses elements offset this.

if you close a lens all the way down the lens will suffer from diffraction, which is where the image is still sharp but light bounces off of the aperture blades, affecting image quality.

finally an "L" lens is Canon's pro line of lenses but unfortunately they come with a pro price as well. they feature things like weather proofing, more coatings, and various high cost elements like ED and aspherical elements.
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  #29  
Old 11-10-2007, 09:01 PM
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Having done a bit of research I think at the moment I'm leaning towards the Canon EF 50mm f/1.4 lens. I have to say the price is very appealing to me.

One thing though, a problem I have at the moment is being able to accurately focus on the stars with what I use. Will I have any such difficulties if I purchase this lens? I wouldn't expect so given what I've been reading, I guess I just need some reassurance

Thanks for all the info guys, I really appreciate it
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  #30  
Old 11-10-2007, 10:05 PM
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Quote:
Originally Posted by Domol View Post
paul,
you siad that you need to "stopped down to around f/3", so what happens if you use the full 1.8 apature? Fuzzy?
Also what's an "L"............that's right i'm a newbie!
Hello,
Check Bill Christie's pics with the 50mm f1.8... very nice!!
http://www.zodiaclight.com/galleria/wideField.htm
Cheers
Doug
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  #31  
Old 12-10-2007, 05:24 AM
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Quote:
Originally Posted by andrew View Post
One thing though, a problem I have at the moment is being able to accurately focus on the stars with what I use. Will I have any such difficulties if I purchase this lens? I wouldn't expect so given what I've been reading, I guess I just need some reassurance
Focusing will still be an issue. It's always an issue and always difficult to get right. It's always something you should spend a lot of time on at the start of your imaging session. Nothing worse than taking a whole run and when you get them back on the computer, realise your focus was slightly off and you have blobby soft stars everywhere.

Take some test exposures (ISO1600 for 10-15 seconds) and zoom in on the LCD to check the tightness of the stars. Go back and forth through the focus repeating the test until you get the smallest tightest stars.

You can also hook your DSLR up to a laptop and use software like DSLRFocus, ImagesPlus and others to do effectively the same thing, but it's using maths to determine the quality of the focus and you just look at the numbers as you go back and forth through focus until you find the lowest number (tightest focus).
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  #32  
Old 12-10-2007, 06:46 AM
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For the 400D look for a freeware program called "Focus Assist". It makes life much easier. I also found that using an on screen magnifier (not the Accessories>Accessibility>Magnifier ) so I can see the pixels makes it much more accurate as well.
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  #33  
Old 12-10-2007, 07:35 AM
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Quote:
Originally Posted by [1ponders] View Post
For the 400D look for a freeware program called "Focus Assist". It makes life much easier. I also found that using an on screen magnifier (not the Accessories>Accessibility>Magnifier ) so I can see the pixels makes it much more accurate as well.
Hi Paul, could you give us a link? I tried to google it but found nothing (except general articles about focus)
BTW, this website has a huge software link library (but not yhis one..) http://astrotips.com/
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  #34  
Old 12-10-2007, 08:19 AM
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Quote:
Originally Posted by dugnsuz View Post
Hello,
Check Bill Christie's pics with the 50mm f1.8... very nice!!
http://www.zodiaclight.com/galleria/wideField.htm
Cheers
Doug
This looks very acceptable, but.. image was taken with lens stopped down to f6.3, so it is not easy to judge... On first occasion (when Melbourne weather permits) I will try my Pentacon 50mm with f6.3 to compare the quality of star images.

What I would really like to see here (or anywhere else) is the simple study of various lenses. cheap and more expensive, with images of reach starfields with some bright stars in the centre and at corners (this milky way is a good test target) taken at the same f settings, so that people can compare apples with apples and pears with pears.
The very good example (but not for what we are talking about here) is this website suggested by mymoon: http://www.samirkharusi.net/televue_canon.html

Unfortunately, most of the time the test reports on lenses (especially if done by non astro-photographers) are very vague, using colourful (poetic even) language with not much real hard data in them.
Also some people belong to Canon club, some to Nikon.. or whatever. Sometimes a lot of money is paid for the specific gear and then it is not easy to admit that almost the same if not better results could have been achieved with significantly lesser investment... the objectivity could be lost very easily if we do not standardize the test method.
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  #35  
Old 12-10-2007, 08:49 AM
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focusing problems... take the lens off auto focus for one if yu havent done so already and swing it around manually to infinity...

unlike canon, with nikon if it fits the camera you can get focus confirmation, even with an adapted lens... but his doesnt help you.
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  #36  
Old 12-10-2007, 09:09 AM
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Originally Posted by ving View Post
focusing problems... take the lens off auto focus for one if yu havent done so already and swing it around manually to infinity...
That will not help either... Mechanical infinity on lens is more than optical infinity...

Also, focus confirmation is not helpful really.
The result depends on how accurate the camera is adjusted (secondary mirror position).

The only way to focus is what Iceman wrote in his reply.. trial and error. But only first time...
If you mark the infinity position on the lens (by lightly scratching it so that you can put it in the same position again), the next time you do not have to repeat the whole procedure.
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  #37  
Old 12-10-2007, 09:15 AM
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FocusAssist

Only works on 400D and possibly 30D
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  #38  
Old 12-10-2007, 09:31 AM
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Originally Posted by [1ponders] View Post
FocusAssist

Only works on 400D and possibly 30D
Paul,
thanks for the link.

That's exactly what I need
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  #39  
Old 12-10-2007, 11:12 AM
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You're welcome. Just remember to name your first DSO discovery after me.

Hmmm... ....[Bok Ponders] has a certain appeal to it
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  #40  
Old 12-10-2007, 12:28 PM
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You're welcome. Just remember to name your first DSO discovery after me.

Hmmm... ....[Bok Ponders] has a certain appeal to it
No worries
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